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Search Results (582)

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22 pages, 10199 KiB  
Article
Novel Benzimidazole-Endowed Chalcones as α-Glucosidase and α-Amylase Inhibitors: An Insight into Structural and Computational Studies
by Prashasthi V. Rai, Ramith Ramu, P. Akhileshwari, Sudharshan Prabhu, Nupura Manish Prabhune, P. V. Deepthi, P. T. Anjana, D. Ganavi, A. M. Vijesh, Khang Wen Goh, Mohammad Z. Ahmed and Vasantha Kumar
Molecules 2024, 29(23), 5599; https://doi.org/10.3390/molecules29235599 - 27 Nov 2024
Viewed by 587
Abstract
In search of novel antidiabetic agents, we synthesized a new series of chalcones with benzimidazole scaffolds by an efficient ‘one-pot’ nitro reductive cyclization method and evaluated their α-glucosidase and α-amylase inhibition studies. The ‘one-pot’ nitro reductive cyclization method offered a simple route for [...] Read more.
In search of novel antidiabetic agents, we synthesized a new series of chalcones with benzimidazole scaffolds by an efficient ‘one-pot’ nitro reductive cyclization method and evaluated their α-glucosidase and α-amylase inhibition studies. The ‘one-pot’ nitro reductive cyclization method offered a simple route for the preparation of benzimidazoles with excellent yield and higher purity compared to the other conventional acid- or base-catalyzed cyclization methods. 1H, 13C NMR, IR, and mass spectrum data were used to characterize the compounds. Single-crystal XRD data confirmed the 3D structure of compound 7c, which was crystalized in the P1¯ space group of the triclinic crystal system. Hirshfeld surface analysis validates the presence of O-H..O, O-H…N, and C-H…O intermolecular hydrogen bonds. From the DFT calculations, the energy gap between the frontier molecular orbitals in 7c was found to be 3.791 eV. From the series, compound 7l emerged as a potent antidiabetic agent with IC50 = 22.45 ± 0.36 µg/mL and 20.47 ± 0.60 µg/mL against α-glucosidase and α-amylase enzymes, respectively. The in silico molecular docking studies revealed that compound 7l has strong binding interactions with α-glucosidase and α-amylase proteins. Molecular dynamics studies also revealed the stability of compound 7l with α-glucosidase and α-amylase proteins. Full article
(This article belongs to the Section Medicinal Chemistry)
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Graphical abstract

Graphical abstract
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<p>Reported antidiabetic agents containing benzimidazole (<b>BN-1–BN-4</b>), chalcone moiety (<b>BN-5–BN-7</b>), and molecules synthesized in present work (<b>7a–l</b>).</p>
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<p>Thermal displacement ellipsoids of compound <b>7c</b> are drawn at the 50% probability.</p>
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<p>Packing of compound <b>7c</b> when viewed down along <span class="html-italic">b</span>-axis involved in hydrogen bond interactions.</p>
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<p>Hirshfeld surface of compound <b>7c</b> mapped with normalized distance contact.</p>
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<p>Hirshfeld surface (<b>a</b>): mapped with curvedness and (<b>b</b>): shape index map of compound <b>7c</b>.</p>
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<p>Fingerprint plots of individual hydrogen contacts of compound <b>7c</b>.</p>
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<p>(<b>A</b>) HOMO/LUMO of compound <b>7c</b>; (<b>B</b>) HOMO/LUMO of compound <b>7l</b>.</p>
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<p>Molecular electrostatic potential map of compound <b>7c</b>.</p>
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<p>Cytotoxicity analysis of compounds <b>7b</b>, <b>7e,</b> and <b>7l</b> against HEK 293 cell lines. (The data are the mean (<span class="html-italic">n</span> = 3) ± SD. One-way ANOVA followed by Dunnett’s post hoc test. The significant levels **** <span class="html-italic">p</span> &lt; 0.0001 when compared with control group (0 μg/mL). * Indicates statistically significant difference).</p>
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<p>Two-dimensional (<b>A</b>) and three-dimensional (<b>B</b>) representation of compound <b>7l</b> interacting with the amino acids of α-glucosidase protein.</p>
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<p>Two-dimensional (<b>A</b>) and three-dimensional (<b>B</b>) representation of compound <b>7l</b> interacting with the amino acids of α-amylase protein.</p>
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<p>Visualization of MD trajectories of compound <b>7l</b> and acarbose complexed with α-glucosidase protein run for 50 ns. (<b>A</b>) Protein–ligand complex RMSD, (<b>B</b>) protein–ligand complex RMSF, (<b>C</b>) protein–ligand complex Rg, (<b>D</b>) protein–ligand complex SASA, (<b>E</b>) ligand hydrogen bonds (red: apoprotein; green: protein–compound <b>7l</b> complex; orange: protein–acarbose complex).</p>
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<p>Visualization of MD trajectories of compound <b>7l</b> and acarbose complexed with α-amylase run for 50 ns. (<b>A</b>) Protein–ligand complex RMSD, (<b>B</b>) protein–ligand complex RMSF, (<b>C</b>) protein–ligand complex Rg, (<b>D</b>) protein–ligand complex SASA, and (<b>E</b>) ligand hydrogen bonds (red: apoprotein; green: protein–compound <b>7l</b> complex; orange: protein–acarbose complex).</p>
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<p>Synthesis of benzimidazole-endowed chalcone derivatives (<b>7a–l</b>). Reagents and conditions: (i) Conc. HNO<sub>3</sub>, Conc.H<sub>2</sub>SO<sub>4</sub>; (ii) methylamine, triethylamine, DMF, RT, 12 h; (iii) 30% NaOH, ethanol, RT, 6–8 h; (iv) sodium dithionite, DMSO, 90 °C, 3–4 h.</p>
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26 pages, 7300 KiB  
Article
Computational Evidence for Bisartan Arginine Blockers as Next-Generation Pan-Antiviral Therapeutics Targeting SARS-CoV-2, Influenza, and Respiratory Syncytial Viruses
by Harry Ridgway, Vasso Apostolopoulos, Graham J. Moore, Laura Kate Gadanec, Anthony Zulli, Jordan Swiderski, Sotirios Tsiodras, Konstantinos Kelaidonis, Christos T. Chasapis and John M. Matsoukas
Viruses 2024, 16(11), 1776; https://doi.org/10.3390/v16111776 - 14 Nov 2024
Viewed by 1231
Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), influenza, and respiratory syncytial virus (RSV) are significant global health threats. The need for low-cost, easily synthesized oral drugs for rapid deployment during outbreaks is crucial. Broad-spectrum therapeutics, or pan-antivirals, are designed to target multiple viral [...] Read more.
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), influenza, and respiratory syncytial virus (RSV) are significant global health threats. The need for low-cost, easily synthesized oral drugs for rapid deployment during outbreaks is crucial. Broad-spectrum therapeutics, or pan-antivirals, are designed to target multiple viral pathogens simultaneously by focusing on shared molecular features, such as common metal cofactors or conserved residues in viral catalytic domains. This study introduces a new generation of potent sartans, known as bisartans, engineered in our laboratories with negative charges from carboxylate or tetrazolate groups. These anionic tetrazoles interact strongly with cationic arginine residues or metal cations (e.g., Zn2+) within viral and host target sites, including the SARS-CoV-2 ACE2 receptor, influenza H1N1 neuraminidases, and the RSV fusion protein. Using virtual ligand docking and molecular dynamics, we investigated how bisartans and their analogs bind to these viral receptors, potentially blocking infection through a pan-antiviral mechanism. Bisartan, ACC519TT, demonstrated stable and high-affinity docking to key catalytic domains of the SARS-CoV-2 NSP3, H1N1 neuraminidase, and RSV fusion protein, outperforming FDA-approved drugs like Paxlovid and oseltamivir. It also showed strong binding to the arginine-rich furin cleavage sites S1/S2 and S2′, suggesting interference with SARS-CoV-2’s spike protein cleavage. The results highlight the potential of tetrazole-based bisartans as promising candidates for developing broad-spectrum antiviral therapies. Full article
(This article belongs to the Special Issue Molecular Epidemiology of SARS-CoV-2, 3rd Edition)
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Figure 1

Figure 1
<p>Docking of experimental sartans (e.g., ACC519TT, Cpd13, BisA, etc.), FDA-approved sartans (e.g., candesartan, olmesartan, losartan, etc.), and known inhibitors (e.g., R1104 and R7335) of the SARS-CoV-2 NSP3 Mac1 domain. (<b>A</b>) Overview of the docking setup showing the X-ray crystallographic structure for the SARS-CoV-2 Mac1 domain, PDB 6YWL, rendered as gray ribbons, and the water-accessible surface (blue shading) with its bound native ligand, ADPR (yellow atoms as spheres). The docking region of interest in which energy grids were constructed is indicated by the walled “periodic” box with colored lines of dimensions (x/red = 26 Å, y/green = 22 Å, and z/blue = 20 Å). (<b>B</b>) Docking results for 27 selected ligands targeting the NSP3 Mac1 domain of SARS-CoV-2. Docking was carried out against two PDB crystallographic structures: 6YWL (blue bars) and 7KQP (light green bars). Ligand docking was performed using AutoDock VINA with AMBER14 force field point charges and dihedral barriers (900 runs per ligand). Docking results are expressed as ligand binding energies (kcal/mol) and calculated dissociation constants (Log10Kd in pM units). Of the 27 docked ligands, Cpd13, a di-phenylcyano-derivative of the anionic bisartan ACC519TT, exhibited the strongest Mac1 binding at 11.45 and 12.41 kcal/mol for the 6YWL and 7KQP Mac1 receptors, respectively. Compared to ACC519TT binding (10.59 and 11.84 kcal/mol, respectively, for binding to the 6YWL and 7KQP receptors), ADPR, which is the native ligand for the Mac1 domain, exhibited somewhat weaker binding (10.32 and 10.07 kcal/mol, respectively, for 6YWL and 7KQP). Surprisingly, compounds R1104 and R7335, which are experimentally proven inhibitors of the NSP3 Mac1 domain [<a href="#B52-viruses-16-01776" class="html-bibr">52</a>], exhibited poor binding energies compared to nearly all the FDA-approved and experimental sartans. (<b>C</b>) Structures of ADPR, the di-phenylcyano-(bisartan)-derivative Cpd13, and bisartan ACC519TT. Chemical key: H, hydrogen; N, nitrogen; O, oxygen; P, phosphorus. (<b>D</b>) Docking validation for ADPR: Docked ADPR pose (green C atoms as spheres) in the Mac1 receptor superimposed onto the 6YWL X-ray structure with bound ADPR (cyan C atoms as spheres). RMSD for the superimposed protein-ligand complexes was ≤ 0.0001 Å. These data indicate that AutoDock VINA was able to accurately calculate the correct X-ray pose for this complex ligand. ADPR was stabilized in the Mac1 domain by approximately six hydrogen bonds (thick yellow dashed lines), as well as pi–pi (red lines) and hydrophobic interactions (green lines). (<b>E</b>) Binding mechanism of Cpd13 (di-phenylcyano-derivative of ACC519TT) in the NSP3 Mac1 domain. The docked ligand was stabilized mainly by ionic pi–cation interactions (thin red lines) between one of the terminal phenylcyano groups and Mac1 residue Phe132. The other phenylcyano group entered hydrophobic interactions (thin green lines) with Phe156 and Ala52. Phe156 also was bonded to the phenyl group adjacent to the benzimidazole group of Cpd13 by pi–cation interactions (thin red or magenta lines). (<b>F</b>) Binding of ACC519TT (yellow C atoms rendered as tubes) in the Mac1 pocket involved numerous hydrophobic interactions (green lines) between the phenyl groups of ACC519TT and residues Ala52, Ile131, Ala129, Pro136, Leu160, Leu126, Val155, Val49, Ile23, and Phe156. Additional pi–pi interactions (red line) were observed between Phe156 and one of the phenyl groups of ACC519TT. Abbreviations: ACC519TT, benzimidazole bis-N,N’-biphenyltetrazole; ACC519T[1], benzimidazole-N-biphenyltetrazole; ADPR, adenosine 5′-diphosphoribose; Ala, alanine; AMBER, Another Model Building Energy Refinement; Asn, asparagine; Asp, aspartic acid; Azil, azilsartan; Bis, bisartan; Cande, candesartan; Epro, eprosartan; EXP3174, Gly, glycine; Irbe, irbesartan; Ile, isoleucine; Leu, leucine; Lo, losartan; Mac1- macrodomain-1; NSP3, non-structural protein 3; Olme, olmesartan; PDB, Protein Data Bank; Phe, phenylalanine; Pro, proline; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; Ser, serine; Telm, telmisartan; Val, valine; Å, angstrom.</p>
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<p>Docking of selected ligands to the SARS-CoV-2 NSP3 PLpro (PDB: 7LBR and 7JRN). Experimentally proven drugs investigated include PLpro inhibitors (i.e., XR8-89 [<a href="#B56-viruses-16-01776" class="html-bibr">56</a>]; GRL0617, Jun9-72-2, and Jun9-74-4 [<a href="#B14-viruses-16-01776" class="html-bibr">14</a>]). <b>Upper panel</b>, (<b>A</b>): The 7LBR PLpro domain X-ray crystallographic structure (blue ribbons) superimposed onto PLpro 7JRN (maroon ribbons). Overall RMSD for aligned structures = 0.478 Å. Approximate boundaries of the docking region, which contained the catalytic Cys11 residue, are indicated by the gray rectangle. The 2-phenylthiophene-based inhibitor “7LBRLignd” (XR8-89) [<a href="#B56-viruses-16-01776" class="html-bibr">56</a>] bound in the “BL2” groove proximal to the catalytic site is also indicated (cyan atoms). The 7LBR structure has been rendered as the Van der Waals surface (yellow shading). <b>Upper panel</b>, (<b>B</b>): Docked bisartan ACC519TT (dusty blue carbon atoms) superimposed on the docked PLpro inhibitor XR8-89 (maroon carbon atoms) for the 7LBR receptor. ACC519TT adopted a conformation along the BL2 groove that was similar to XR8-89 (molecule pair RMSD = 9.49 Å), with both ligands sharing a number of close contacts with 7LB6 residues, including Leu162, Tyr273, Tyr264, Pro299, Tyr268, and Gln269. Non-bond drug–receptor interactions included hydrophobic (green lines), pi–pi resonance (red lines), cation–pi (blue to light-blue lines), and hydrogen bonds (dashed yellow lines). Locations of the dual anionic tetrazole groups are labeled in blue as Tet#1 and Tet#2. <b>Upper panel</b>, (<b>C</b>): The bisartan tetrazole functionalities appeared bioisosteric with the terminal aminocyclobutane and cyclopentane groups of XR8-89. A similar relationship was observed for the central benzimidazole group of ACC519TT that overlapped the central benzene ring of XR8-89. <b>Lower panel</b>, (<b>D</b>): Docking results expressed as ligand binding energies in kcal/mol. Log<sub>10</sub>Kd values in pM units were computed from the binding energies [<a href="#B32-viruses-16-01776" class="html-bibr">32</a>]: color key: blue bars = docking to the PLpro domain of PDB 7LBR and green bars = docking to the PLpro domain of PDB 7JRN. Abbreviations: ACC519TT, benzimidazole <span class="html-italic">bis</span>-<span class="html-italic">N,N′</span>-biphenyltetrazole; ACC519T[1], benzimidazole-<span class="html-italic">N</span>-biphenyltetrazole; Azil, azilsartan; Bis, bisartan; Cande, candesartan; cpd, compound; DIZE, diminazene aceturate; Epro, eprosartan; Gln, glutamine; Gly, glycine; Irbe, irbesartan; Leu, leucine; Lo, losartan; Mac1, macrodomain-1; Met, methionine; Nirmat, nirmatrelvir; NSP3, non-structural protein 3; Olme, olmesartan; PLpro, papain-like protease; Pro, proline; RMSD, root-mean-standard deviation; RSV, respiratory syncytial virus; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; Tyr, tyrosine; XR8-89, 7:BR-Ligand; Å, Angstrom.</p>
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<p>(<b>A</b>) Docking results of selected ligands targeting the RSV F-postfusion (i.e., drug-induced) protein that mediates virus entry into host cells. In its native (host-free) state, the homotrimeric F-protein exists in a metastable “prefusigenic or prefusion” conformation and must undergo a structural rearrangement that facilitates membrane fusion [<a href="#B61-viruses-16-01776" class="html-bibr">61</a>]. Ligands were docked into the three-fold symmetric domain (3FSD) of the virion F-protein (PDB 5EA4) located in the upper (surface) central cavity where the three chains intersect, denoted in the side-view projection by the red square in (<b>B</b>). Induced-fit binding of the potent RSV F-protein inhibitor JNJ-49153390 within the 3FSD interlocks two of the protomers in the pocket, effectively stabilizing the prefusion conformation and preventing host cell fusion and infection. Docking results indicated the bisartan ACC519TT bound significantly more strongly (12.53 kcal/mol) into the 3FSD pocket compared to all other drugs tested. The binding energy of JNJ-49153390 (8.28 kcal/mol), as well as those of two other structurally similar experimentally proven F-protein inhibitors (i.e., cpd2-5EA4 and cpd44-5EA4) were substantially lower. (<b>C</b>) Structure of 5EA4 with docked ACC519TT (in the drug-bound postfusogenic conformation) showing the three color-coded protomers (Key: yellow = Chain-A; magenta = Chain-B; gray = Chain-C) in the down-axis view rotated 90° from the side view in B. (<b>D</b>) Magnified down-axis view from C showing binding mechanism of ACC519TT involving a putative tethering of all three protomers by interactions with symmetrically arranged 5EA4 residues Phe488 and Phe140 (in each chain). Unlike the binding of JNJ-49153390, ACC519TT binding also involved strong electrostatic (salt bridge/pi–cation) interactions (blue lines) of the tetrazole#2 (Tet#2) functional group with a deeply buried Arg339 residue in Chain-B. The tetrazole#1 (Tet#1) group of ACC519TT was effectively coordinated by two of the symmetrically arranged phenylalanine residues (Phe488-A and Phe488-C) through pi–pi resonance bonding (red lines). This type of dual protomer binding by ACC519TT was similar to that reported by Battles and coworkers [<a href="#B61-viruses-16-01776" class="html-bibr">61</a>] regarding JNJ-49153390. Finally, additional hydrophobic interactions (green lines) between Phe140-C and one of the phenyl groups proximal to Tet#1 and adjacent to the central benzimidazole moiety also contributed to ACC519TT stability in the 3FSD pocket. (<b>E</b>) Side-view image rotated 90° from D showing docked ACC519TT (yellow C atoms) superimposed onto the X-ray crystallographic pose of the F-protein antagonist JNJ-41953390 (magenta C atoms). This view illustrates more clearly the interaction of Tet#2 with the buried Arg339 residue of Chain-B through ionic (blue lines) and hydrogen bonding (thick dashed yellow line). (<b>F</b>) Chemical structures of the six ligands evaluated. Chemical key: O. oxygen; S, sulfur; Br, bromine; N, nitrogen. Abbreviations: ACC519TT, benzimidazole <span class="html-italic">bis</span>-<span class="html-italic">N,N′</span>-biphenyltetrazole; ACC519T[1], benzimidazole-<span class="html-italic">N</span>-biphenyltetrazole; Asp, aspartic acid; Arg, arginine; cpd, compound; F-protein, fusion protein; PDB, Protein Data Bank; Phe, phenylalanine; RSV, respiratory syncytial virus; S, sulfur; Tet, tetrazole; JNJ49153390, 5EA4-Ligand; 3FSD, 3-fold-symmetric domain.</p>
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<p>Binding of bisartan ACC519TT to the furin cleavage sites of the SARS-CoV-2 spike (S) protein. (<b>A</b>) Full-sequence homology model (Swiss Model 05) of the SARS-CoV-2 spike protein showing locations of the S’ and S1/S2 FCSs. The three homotrimeric chains are color coded: Chain-A = yellow with Van der Waals surface (yellow shading); Chain-B = green; Chain-C = blue. The model is rotated so that the S2′ FCS of Chain-A with docked bisartan ACC519TT (cyan carbon atoms) is shown located in the center of the model. (<b>B</b>) Docked pose of bisartan ACC519TT in the S1/S2 spike FCS consensus loop region showing the interaction of tetrazole#1 (Tet#1) with Arg685. (<b>C</b>) ACC519TT conformation following 90 ns of an NPT MD simulation at 311 °K, 0.9%wt/vol saline with periodic boundaries (see Methods) of an isolated model “fragment” of the S1/S2 FCS binding domain depicted in (<b>E</b>). Water and NaCl ions have been hidden for clarity. The four terminal fragment residues of the FCS model in (<b>E</b>) were capped and frozen during the MD simulation. Analysis of the MD trajectory indicated the total system energy was essentially equilibrated throughout the simulation (blue line in (<b>F</b>)). Despite the significant thermal motion of the FCS model (RMSD ranged from about 1 to 4 Å), the bisartan remained stably bound for the 90 ns duration of the MD simulation (drug RMSD ranged from about 1 to 5 Å). The comparison of the initial docked drug pose in (<b>B</b>) with that following the MD simulation (<b>C</b>) revealed that the bound ligand re-oriented, abandoning its initial Tet#1 interaction with Arg685 and establishing new stabilizing interactions with Arg residues 682 and 683 via ionic pi–cation bonding mechanisms (blue lines). Additional drug–receptor bond types included hydrophobic (green lines) and pi–pi (red lines) interactions. (<b>D</b>) Magnified view of the conformational pose of bisartan ACC519TT in the S2′ FCS pocket following VINA docking (see Methods). Details of the ligand–receptor interactions in the S2′ site are shown to the right (blue arrow). Color key: thin colored lines = primary intermolecular interactions; green = hydrophobic interactions; red = pi–pi; magenta = ionic; blue = pi–cation. Abbreviations: ACC519TT, benzimidazole <span class="html-italic">bis</span>-<span class="html-italic">N,N′</span>-biphenyltetrazole; Ala, alanine; Arg, arginine; Cys, cysteine; FCS, furin cleavage site; Ile, isoleucine; Gln, glutamine; Glu, glutamic acid; Gly, glycine; His, histidine; Leu, leucine; Lys, lysine; Phe, phenylalanine; Pro, proline; RMSD, root-mean-standard deviation; S, subunit; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; Ser, serine; Tet, tetrazole; Thr, threonine; Tyr, tyrosine.</p>
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<p>Docking of three FDA-approved drugs (orange borders), experimental drugs (purple borders), theoretical tri-tetrazole compounds (green borders), and our imidazole-biphenyltetrazole, ACC519TT (black border) to five influenza neuraminidases from the PDB. The four-letter name prefixes indicate the PDB complex from which the ligand was extracted prior to docking to the Arg-rich catalytic pocket of the apo-receptor. The number of AutoDock VINA runs per ligand ranged from 100 to 300 using AMBER14 charges and parameters. Abbreviations: ACC519TT, benzimidazole <span class="html-italic">bis</span>-<span class="html-italic">N,N′</span>-biphenyltetrazole; AMBER, Another Model Building Energy Refinement; Arg, arginine; PDB, Protein Data Bank. Chemical key: H, hydrogen; N, nitrogen; O, oxygen; S, sulfur.</p>
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<p>Mechanism of bisartan ACC519TT interactions with residues comprising the different neuraminidase catalytic domains. In four of the five neuraminidase models (i.e., 2HTQ, 6BR6, 6HP0, and 2HTU) both anionic tetrazole groups of the bisartan formed strong salt bridges (blue lines = cation–pi interactions) with two or more cationic arginine residues (carbon represented by yellow spheres). In the case of 2HU0, only one of the terminal tetrazole groups formed bonds with arginine residues (R371 and R118). The other tetrazole group formed pi–pi (red lines) and hydrophobic (green lines) interactions with Tyr347. In all the cases, the ligand displayed a “wrapped” conformation in which the tetrazole moieties were docked into positions relatively close to one another. Abbreviations: ACC519TT, benzimidazole <span class="html-italic">bis</span>-<span class="html-italic">N,N′</span>-biphenyltetrazole; Ala, alanine; Arg, arginine; Asn, asparagine; Asp, aspartate; Glu, glutamic acid; Ile, isoleucine; Lys, lysine; Pro, proline; Ser, serine; Thr, threonine; Trp, tryptophan; Tyr, tyrosine; Val, valine.</p>
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<p>Equilibrium MD of ACC519TT docked in the neuraminidase 6BR6 catalytic site (NVT ensemble, 311 °K, 0.9 wt/% NaCl, pH 7.4). (<b>A</b>) Cuboid periodic cell with boundaries = 8.0 Å from any protein atom (Na and Cl atoms are shown as yellow and green balls in solution). (<b>B</b>) Docked ACC519TT (gray carbon atoms) at t = 0 ns showing main interactions with 6BR6 receptor (Key: green lines = hydrophobic; blue lines = salt bridge [cation–pi]; and red lines = pi–pi). (<b>C</b>) <b>Upper panel:</b> Ligand binding energy in kcal/mol (blue line); note that higher values = stronger binding to the receptor. Orange line = overall system potential energy. <b>Middle panel:</b> Frame captures of the ligand–receptor complex at designated intervals (ns). <b>Lower panel:</b> Ligand radius of gyration, RMSD (blue and orange lines, respectively), and receptor RMSD (gray line). The ligand remained stably bound in the pocket for the duration of the 36 ns run simulation. This stability was reflected in the relatively consistent ligand–receptor binding energy (blue line, upper panel). Abbreviations: ACC519TT, benzimidazole <span class="html-italic">bis</span>-<span class="html-italic">N,N′</span>-biphenyltetrazole; Arg, arginine; Asp, aspartic acid; Glu, glutamic acid; His, histidine; Lys, lysine; MD, molecular dynamics; RMSD, root-mean-standard deviation; Tyr, tyrosine; Val, valine; Å, angstrom.</p>
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<p>(<b>A</b>) Minimum-energy ACC519TT–neuraminidase complex (at about 10.5 ns) extracted from the 36 ns MD trajectory of 6BR6. Blue transparent shading corresponds to the 6BR6 water-accessible surface. (<b>B</b>) The anionic tetrazole groups form stable salt-bridge (cation–pi) interactions (blue lines) involving R118, R292, and R371. These are the same three Arg residues that were involved in bonding with the dual anionic tetrazole groups of ACC519TT in the original docked configuration at t = 0 ns. Abbreviations: ACC519TT, benzimidazole <span class="html-italic">bis</span>-<span class="html-italic">N,N′</span>-biphenyltetrazole; Arg, arginine; Glu, glutamic acid; Ile, isoleucine; His, histidine; Lys, lysine; MD, molecular dynamics; Thr, threonine; Tyr, tyrosine; Val, valine.</p>
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<p>Re-docking of extracted native ligands into the catalytic pocket of the five neuraminidase models evaluated. In each case, the X-ray crystallographic structure (dusty blue carbon atoms) was superimposed against the docked complex (maroon carbon atoms) before calculating the RMSD values for the superimposed ligands. Docking to 6HP0 (RMSD = 2.7141 Å) and 2HTQ (RMSD = 0.9092 Å) yielded the best fit with their respective X-ray conformations, whereas poorer-quality fits were observed for PDB 2HU0 (RMSD = 3.2189 Å), 6BR6 (RMSD = 5.0573 Å), and 2HTU (RMSD = 4.7050 Ang). Abbreviations: Ala, alanine; Arg, arginine; Asn, asparagine; Asp, aspartic acid; His, histidine; Ile, isoleucine; Glu, glutamic acid; PDB, Protein Data Bank; RMSD, root-mean-square deviation; Ser, serine, Trp, tryptophan, Tyr, tyrosine; Å, angstrom.</p>
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<p>Docking data comparing VINA binding energies and per-atom efficiencies for 10 drugs against three different neuraminidase receptors: neuraminidase in complex with sialic acid, its single mutant 1×Mut (R153A), and the triple mutant 3×Mut (R153A-R294A-R372A).</p>
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19 pages, 2412 KiB  
Article
N-Aryl Benzimidazole and Benzotriazole Derivatives and Their Hybrids as Cytotoxic Agents: Design, Synthesis and Structure–Activity Relationship Studies
by Yulia R. Aleksandrova, Natalia S. Nikolaeva, Inna A. Shagina, Karina D. Smirnova, Alla A. Zubishina, Alexander I. Khlopotinin, Artem N. Fakhrutdinov, Alexander L. Khokhlov, Roman S. Begunov and Margarita E. Neganova
Molecules 2024, 29(22), 5360; https://doi.org/10.3390/molecules29225360 - 14 Nov 2024
Viewed by 693
Abstract
The era of chemotherapy began in the 1940s, which is the basis of traditional antitumor approaches and, being one of the most high-tech treatment methods, is still widely used to treat various types of cancer. A promising direction in modern medicinal chemistry is [...] Read more.
The era of chemotherapy began in the 1940s, which is the basis of traditional antitumor approaches and, being one of the most high-tech treatment methods, is still widely used to treat various types of cancer. A promising direction in modern medicinal chemistry is currently the creation of hybrid molecules containing several pharmacophore fragments of different structures. This strategy is successfully used to increase the therapeutic efficacy of cytotoxic agents and reduce side effects. In this work, we synthesized 10 1-aryl derivatives of benzimidazole and benzotriazole and 11 hybrids based on them. Among the compounds obtained, the most promising hybrid molecules were diphenylamines, containing an amino group and a benzotriazole cycle in the ortho position to the bridging NH group, which showed significant cytotoxic activity, excellent antioxidant properties and the ability to suppress the migration activity of tumor cells. Taken together, our results demonstrate that substituted diphenylamine-based bipharmacophoric compounds may serve as a promising platform for further optimization to obtain effective antitumor compounds. Full article
(This article belongs to the Special Issue Synthesis and Properties of Heterocyclic Compounds: Recent Advances)
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<p>Some examples of azaheterocycle-containing diphenylamines with anticancer activity.</p>
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<p>Chemical structures of synthesized hybrid molecules, which are active pharmaceutical ingredients. (<b>A</b>) Fused hybrid; (<b>B</b>) a hybrid with a linker.</p>
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<p>Effect of <b>6a</b>–<b>d</b> on the lipid peroxidation of rat brain homogenate (2 mg/mL) initiated by Fe(II)-500 μM. (<b>a</b>) Histograms reflecting the content of malondialdehyde in samples under the action of compounds at a concentration of 100 μM. (<b>b</b>) Curves of the “concentration–effect” dependence, reflecting the calculation of the values of IC<sub>50</sub> inhibiting the lipid peroxidation effect. The concentration of the substances ranged from 1 to 300 μM. To assess the statistical significance, a one-sided ANOVA and the Dunnett multiple comparison test were used, where ****, <span class="html-italic">p</span> &lt; 0.0001, when compared to a control taken as 100%.</p>
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<p>The ability of diphenylamines <b>6b</b>, <b>6c</b> and <b>6d</b> to modulate the migratory ability and proliferative potential of A549 cells, studied using the scratch test. Representative images of defect healing, taken immediately after the scratch was applied and 24, 48 and 72 h after cell treatment with the test substances (×40).</p>
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<p>Histogram showing the area of the scratch overgrowth of A549 cells under the action of 2-aminodiphenylamines <b>6b</b>, <b>6c</b> and <b>6d</b> at different time intervals. The concentration of the studied compounds was 1 μM; the control samples contained an equivalent volume of solvent (1% DMSO). **—<span class="html-italic">p</span> ≤ 0.01; ***—<span class="html-italic">p</span> ≤ 0.001 (two-way ANOVA, the Bonferroni post hoc test).</p>
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<p>Synthesis of novel hybrid molecules <b>5a</b>–<b>d</b>, <b>6a</b>–<b>d</b> and <b>7a</b>–<b>c.</b> Reagents and conditions: (<b>i</b>) K<sub>2</sub>CO<sub>3</sub>, DMF, 110 °C for 2 h of <b>3a</b>, 3 h of <b>3c,d</b> or 7 h of <b>3b,e</b>; (<b>ii</b>) TiCl<sub>3</sub>, 10% HCl, <span class="html-italic">i</span>-PrOH, 70 °C, 5 min; (<b>iii</b>) <b>2a</b> or <b>2b</b>, K<sub>2</sub>CO<sub>3</sub>, DMF, 110 °C, 12 h; (<b>iv</b>) TiCl<sub>3</sub>, 10% HCl, <span class="html-italic">i</span>-PrOH, 70 °C, 5 min; (<b>v</b>) HCOOH, DMF, 1 h, 90 °C.</p>
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<p>Destruction of hydrogen bonds in the putative benzotriazole dimer in DMF solution under the influence of temperature.</p>
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<p>Synthesis of <span class="html-italic">N</span>-(2-(1<span class="html-italic">H</span>-benzimidazol-1-yl)-5-(trifluoromethyl)phenyl)hydroxylamine (<b>8a</b>) and <span class="html-italic">N</span>-(2-(1<span class="html-italic">H</span>-benzotriazol-1-yl)-5-(trifluoromethyl)phenyl)hydroxylamine (<b>8b</b>)<b>.</b> Reagents and conditions: (i) SnCl<sub>2</sub>∙2H<sub>2</sub>O, 18% HCl, <span class="html-italic">i</span>-PrOH, 70 °C, 5 min.</p>
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6 pages, 725 KiB  
Communication
Water-Mediated Synthesis of (E)-3-(1-Methyl-1H-benzo[d]imidazol-5-yl)-N-phenethylacrylamide, a Caffeic Acid Phenethyl Amide Analogue
by Muppidi Subbarao and Sean M. Kerwin
Molbank 2024, 2024(4), M1915; https://doi.org/10.3390/M1915 - 12 Nov 2024
Viewed by 439
Abstract
Caffeic acid phenethyl ester (CAPE) is a phenolic natural product with diverse biological activities, notably anticancer properties. However, its ester group is metabolically unstable. The amide derivative, CAPA, offers improved metabolic stability to esterases but still possesses a metabolically liable catechol group. In [...] Read more.
Caffeic acid phenethyl ester (CAPE) is a phenolic natural product with diverse biological activities, notably anticancer properties. However, its ester group is metabolically unstable. The amide derivative, CAPA, offers improved metabolic stability to esterases but still possesses a metabolically liable catechol group. In this work, we describe the synthesis of a novel CAPA analogue in which the catechol is replaced with a benzimidazole bioisostere via a water-mediated Wittig reaction. Full article
(This article belongs to the Section Natural Product Chemistry)
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<p>Structure of CAPE and CAPA and the benzimidazole CAPA analogue <b>1</b>.</p>
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<p>Synthesis of 1-methyl-1<span class="html-italic">H</span>-benzo[<span class="html-italic">d</span>]imidazole-5-carbaldehyde <b>7</b>. Conditions: a. MeOH, H<sub>2</sub>SO<sub>4</sub>, 60 °C (95%); b. MeNH<sub>2</sub>, MeOH, (quant.); c. Zn, NH<sub>4</sub>Cl, THF/H<sub>2</sub>O/MeOH, 0 °C (91%); d. formic acid, 150 °C (µwave), (77%); e. LAH, THF (81%); f. DMSO, (ClCO)<sub>2</sub>, Et<sub>3</sub>N, DCM, (85%).</p>
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<p>Synthesis of(<span class="html-italic">E</span>)-3-(1-methyl-1H-benzo[d]imidazol-5-yl)-N-phenethylacrylamide.</p>
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5 pages, 1563 KiB  
Short Note
Dichloro-bis[(Z)-1-styryl-benzimidazole]-zinc(II)
by Neslihan Şahin, İsmail Özdemir and David Sémeril
Molbank 2024, 2024(4), M1913; https://doi.org/10.3390/M1913 - 5 Nov 2024
Viewed by 414
Abstract
We have successfully synthesized the dichloro-bis[(Z)-1-styryl-benzimidazole]-zinc(II) complex, which was fully characterized by IR, elemental analysis, and mass and NMR spectroscopy. The solid-state structure definitively shows that two benzimidazole moieties are coordinated to the zinc atom, which adopts a tetrahedral geometry. Full article
(This article belongs to the Section Structure Determination)
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<p>Targeted zinc(II) complex <b>2</b>.</p>
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<p><sup>1</sup>H NMR spectra of 1-styryl-benzimidazole (<b>1</b>) (top) and its corresponding dichloro-bis[(<span class="html-italic">Z</span>)-1-styryl-benzimidazole]-zinc(II) (<b>2</b>) complex (bottom) in CDCl<sub>3</sub>.</p>
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<p>ORTEP drawing of the zinc(II) complex <b>2</b> (50% probability thermal ellipsoids).</p>
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<p>Synthesis of zinc complex <b>2</b>.</p>
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5 pages, 1162 KiB  
Short Note
Dichloro-Bis(1-cinnamyl-benzimidazole)-Cobalt(II)
by Neslihan Şahin, İsmail Özdemir and David Sémeril
Molbank 2024, 2024(4), M1911; https://doi.org/10.3390/M1911 - 31 Oct 2024
Viewed by 609
Abstract
Dichloro-bis(1-cinnamyl-benzimidazole)-cobalt(II) was prepared in one step using a cobalt precursor CoCl2 and corresponding substituted benzimidazole. The complex was fully characterized using IR, elemental analysis, and mass- and NMR spectroscopy. In the solid state, the cobalt atom displays a typical tetrahedral geometry and [...] Read more.
Dichloro-bis(1-cinnamyl-benzimidazole)-cobalt(II) was prepared in one step using a cobalt precursor CoCl2 and corresponding substituted benzimidazole. The complex was fully characterized using IR, elemental analysis, and mass- and NMR spectroscopy. In the solid state, the cobalt atom displays a typical tetrahedral geometry and is coordinated to two chlorine atoms and two benzimidazole moieties. Full article
(This article belongs to the Section Structure Determination)
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<p>Targeted cobalt(II) complex, <b>2</b>, incorporating two cinnamyl-benzimidazole moieties.</p>
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<p>ORTEP diagram of cobalt(II) complex <b>2</b> (50% probability thermal ellipsoids). Important bond lengths (Å) and angles (°): Co1-N1 2.006(3), Co1-N3 1.998(3), Co1-Cl1 2.2521(11), Co1-Cl2 2.2559(12), N1-C1 1.316(5), C1-N2 1.354(5), N2-C2 1.384(5), C2-C7 1.396(5), C7-N1 1.393(5), N3-C17 1.324(5), C17-N4 1.342(5), N4-C18 1.391(5), C18-C23 1.378(5), C23-N3 1.400(5), N1-Co1-N3 116.07(13), Cl1-Co1-Cl2 116.37(5), Cl1-Co1-N1 104.09(10), N1-Co1-Cl2 108.10(10), Cl2-Co1-N3 108.46(10), N3-Co1-Cl1 104.01(10), C1-N1-Co1 123.2(3), C7-N1-Co1 130.5(3), C17-N3-Co1 124.8(3), and C23-N3-Co1 130.7(3).</p>
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<p>Self-organized structure of complex <b>2</b> formed <span class="html-italic">via</span> CH•••Cl interactions (in red).</p>
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<p>Synthesis of cobalt(II) complex <b>2</b>.</p>
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12 pages, 2035 KiB  
Article
Catalytic Behavior of NHC–Silver Complexes in the Carboxylation of Terminal Alkynes with CO2
by Assunta D’Amato, Marco Sirignano, Francesco Viceconte, Pasquale Longo and Annaluisa Mariconda
Inorganics 2024, 12(11), 283; https://doi.org/10.3390/inorganics12110283 - 30 Oct 2024
Viewed by 418
Abstract
A number of N-heterocyclic carbene–silver compounds (NHCs)AgX were tested in the direct carboxylation of terminal alkynes using carbon dioxide as the C1 carbon feedstock. The reactions proceed at a pressure of 1 atm of CO2 at room temperature, in the presence of [...] Read more.
A number of N-heterocyclic carbene–silver compounds (NHCs)AgX were tested in the direct carboxylation of terminal alkynes using carbon dioxide as the C1 carbon feedstock. The reactions proceed at a pressure of 1 atm of CO2 at room temperature, in the presence of Cs2CO3, and using silver–NHC complexes as catalysts. Thus, phenylacetylene and several alkynes are converted to the corresponding propiolic acids in good to high conversions. The activity of the catalysts is strongly influenced by the substituents on the NHC backbone and the nature of the counterion. Specifically, the most active compound exhibits iodide as the counterion and is stabilized by a benzimidazole derivative. After 24 h of reaction, a quantitative conversion is obtained utilizing DMF as the solvent and phenylacetylene as the substrate. Full article
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<p>Examples of conversion reactions of propiolic acids in organic synthesis.</p>
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<p>Hypothesized mechanism for the silver–NHC catalyzed carboxylation of terminal alkynes.</p>
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<p>Synthesis of NHC–silver(I) complexes <b>1–3a</b> and <b>4a–c</b>.</p>
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<p>Synthetic routes for the exchange of the counterion.</p>
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<p>Kinetic profile of 4a in the reaction.</p>
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16 pages, 2860 KiB  
Article
Computational Approach to Identifying New Chemical Entities as Elastase Inhibitors with Potential Antiaging Effects
by Giovanna Pitasi, Andrea Brancale, Sonia Floris, Antonella Fais, Rosaria Gitto and Laura De Luca
Int. J. Mol. Sci. 2024, 25(20), 11174; https://doi.org/10.3390/ijms252011174 - 17 Oct 2024
Viewed by 639
Abstract
In the aging process, skin morphology might be affected by wrinkle formation due to the loss of elasticity and resilience of connective tissues linked to the cleavage of elastin by the enzymatic activity of elastase. Little information is available about the structural requirements [...] Read more.
In the aging process, skin morphology might be affected by wrinkle formation due to the loss of elasticity and resilience of connective tissues linked to the cleavage of elastin by the enzymatic activity of elastase. Little information is available about the structural requirements to efficiently inhibit elastase 1 (EC 3.4.21.36) expressed in skin keratinocytes. In this study, a structure-based approach led to the identification to the pharmacophoric hypotheses that described the main structural requirements for binding to porcine pancreatic elastase as a valuable tool for the development of skin therapeutic agents due to its similarity with human elastase 1. The obtained models were subsequently refined through the application of computational alanine-scanning mutagenesis to evaluate the effect of single residues on the binding affinity and protein stability; in turn, molecular dynamic simulations were carried out; these procedures led to a simplified model bearing few essential features, enabling a reliable collection of chemical features for their interactions with elastase. Then, a virtual screening campaign on the in-house library of synthetic compounds led to the identification of a nonpeptide-based inhibitor (IC50 = 60.4 µM) belonging to the class of N-substituted-1H-benzimidazol-2-yl]thio]acetamides, which might be further exploited to obtain more efficient ligands of elastase for therapeutic applications. Full article
(This article belongs to the Section Molecular Pharmacology)
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<p>Non-peptide-based inhibitors of elastase that have reached (pre)clinical development.</p>
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<p>Chemical structures of the five ligands bound to PPE in the selected ligand/protein complexes available on PDB database (PDB codes: 1 BMA, 1 BTU, 1 ELE, 1 HV7, 1 JIM) [<a href="#B23-ijms-25-11174" class="html-bibr">23</a>,<a href="#B35-ijms-25-11174" class="html-bibr">35</a>,<a href="#B36-ijms-25-11174" class="html-bibr">36</a>,<a href="#B37-ijms-25-11174" class="html-bibr">37</a>,<a href="#B38-ijms-25-11174" class="html-bibr">38</a>].</p>
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<p>(<b>A</b>–<b>E</b>). The 3D structure-based pharmacophore models of PPE bound to different inhibitors derived from X-ray structure of complexes with PDB ID: (<b>A</b>) 1 BMA, (<b>B</b>) 1 BTU, (<b>C</b>) 1 ELE, (<b>D</b>) 1 HV7 and (<b>E</b>) 1 JIM (from references [<a href="#B23-ijms-25-11174" class="html-bibr">23</a>,<a href="#B35-ijms-25-11174" class="html-bibr">35</a>,<a href="#B36-ijms-25-11174" class="html-bibr">36</a>,<a href="#B37-ijms-25-11174" class="html-bibr">37</a>,<a href="#B38-ijms-25-11174" class="html-bibr">38</a>]). Target amino acids are shown as gray-colored sticks. Hydrophobic features are shown as yellow spheres, while hydrogen bond acceptors and donors are represented as red and green arrows, respectively.</p>
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<p>Schematic representation of the contributions of ΔΔG<span class="html-italic"><sub>stability</sub></span> analyzed by using Alanine scanning module in Schrodinger. Each colored bar displays the interaction between each PDB structure and key amino acid residues. The red line represents the threshold of ΔΔG<span class="html-italic"><sub>stability</sub></span> &gt; 3 Kcal/mol.</p>
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<p>Merged pharmacophore composed of six hydrophobic features (yellow spheres, H<sub>1</sub>–H<sub>6</sub>), two hydrogen bond acceptors (red arrows, A<sub>1,2</sub>), one hydrogen bond donor (green arrow, D<sub>1</sub>), and one aromatic ring (Ar<sub>1</sub>). The table shows the label of the features and the corresponding amino acid residues involved in the interaction.</p>
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<p>Molecular dynamics results of complexes of 1 BMA (<b>A</b>), 1 BTU (<b>B</b>), 1 ELE (<b>C</b>), 1 HV7 (<b>D</b>), and 1 JIM (<b>E</b>). Interactions that occurred for more than 30% of the simulation time were examined.</p>
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<p>Refined pharmacophore model for elastase inhibitors composed of two hydrophobic features (yellow spheres, H<sub>2</sub>, H<sub>4,5</sub>), two hydrogen bond acceptor features (red arrows, A<sub>1</sub>–A<sub>2</sub>), one hydrogen bond donor (green arrow, D<sub>1</sub>). The table shows the label of the features and the corresponding amino acid residues involved in the interaction.</p>
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<p>Mapping of the five chemical features 2 HY (H<sub>2</sub>, H<sub>4,5</sub>), 2 HBA (A<sub>1</sub>, A<sub>2</sub>), 1 HBD (D<sub>1</sub>) on <span class="html-italic">N</span>-substituted-1H-benzimidazol-2-yl]thio]acetamides (<b>1</b>–<b>7</b>) selected by virtual screening. Red circle for hydrogen bond acceptor feature; green circle for hydrogen bond donor feature; yellow circle for hydrophobic feature.</p>
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<p>(<b>A</b>) Plausible binding mode of compound <b>2</b> (green stick) in the cavity of elastase protein structure (gray). The hydrogen bond is represented as yellow dashes. This figure was prepared using the program PyMOL (<a href="https://www.pymol.org" target="_blank">https://www.pymol.org</a> accessed on 14 August 2024, The PyMOL Molecular Graphics System, Version 3.0 Schrödinger, LLC., New York, NY, USA). (<b>B</b>) Schematic 2D representation of the interactions between compound <b>2</b> and PPE, the interactions were generated by Maestro.</p>
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22 pages, 2306 KiB  
Review
From Deworming to Cancer Therapy: Benzimidazoles in Hematological Malignancies
by Upendarrao Golla, Satyam Patel, Nyah Shah, Stella Talamo, Riya Bhalodia, David Claxton, Sinisa Dovat and Arati Sharma
Cancers 2024, 16(20), 3454; https://doi.org/10.3390/cancers16203454 - 12 Oct 2024
Viewed by 1234
Abstract
Drug repurposing is a strategy to discover new therapeutic uses for existing drugs, which have well-established toxicity profiles and are often more affordable. This approach has gained significant attention in recent years due to the high costs and low success rates associated with [...] Read more.
Drug repurposing is a strategy to discover new therapeutic uses for existing drugs, which have well-established toxicity profiles and are often more affordable. This approach has gained significant attention in recent years due to the high costs and low success rates associated with traditional drug development. Drug repositioning offers a more time- and cost-effective path for identifying new treatments. Several FDA-approved non-chemotherapy drugs have been investigated for their anticancer potential. Among these, anthelmintic benzimidazoles (such as albendazole, mebendazole, and flubendazole) have garnered interest due to their effects on microtubules and oncogenic signaling pathways. Blood cancers, which frequently develop resistance and have high mortality rates, present a critical need for effective therapies. This review highlights the recent advances in repurposing benzimidazoles for blood malignancies. These compounds induce cell cycle arrest, differentiation, tubulin depolymerization, loss of heterozygosity, proteasomal degradation, and inhibit oncogenic signaling to exert their anticancer effects. We also discuss current limitations and strategies to overcome them, emphasizing the potential of combining benzimidazoles with standard therapies for improved treatment of hematological cancers. Full article
(This article belongs to the Special Issue Drug Repurposing and Reformulation for Cancer Treatment: 2nd Edition)
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<p>Structure of various benzimidazole derivatives that are approved by the FDA as anthelmintic agents. Among these, parbendazole, fenbendazole, oxfendazole, and oxibendazole are used to treat animals, while albendazole, mebendazole, ricobendazole, and flubendazole are used for fighting parasite infections in humans.</p>
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<p>The spectrum of biological activities associated with benzimidazole-based derivatives for human use. Conventionally, benzimidazoles were approved as anthelmintic/antiparasitic agents, and later several other derivatives were developed. Currently, the exploration of benzimidazoles and their derivatives for their anticancer activity is of great interest to researchers.</p>
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<p>Broad mechanisms of action of benzimidazoles as anticancer agents. Benzimidazole derivatives inhibit cell cycle, invasion/metastasis, tubulin polymerization, oncogenic signaling, angiogenesis, and cell viability, along with increasing apoptosis, autophagy, and terminal differentiation for reducing the cancer progression.</p>
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<p>Mechanisms of action of anthelmintic benzimidazole-based derivatives as anti-leukemic agents. As a classical anthelmintic, BMDZs inhibit tubulin polymerization (<b>A</b>) to induce cell death by mitotic cell arrest (<b>B</b>). Albendazole (ABZ) known to accelerate chromosomal missegregation and thus induces loss of heterozygosity in mammalian cells (<b>C</b>). Some BMDZs are known to induce terminal differentiation of leukemic blast cells to granulocytes and/or monocytes and thus cause cell death (<b>D</b>). Treatment with BMDZs promotes proteasomal degradation of transcriptional factors such as GLI and c-Myb, which play a vital role in leukemia development and progression (<b>E</b>). Also, these BMDZs inhibit several oncogenic signaling pathways (Notch1, PI3K/AKT, NF-κB) to achieve remission during the treatment of hematological malignancies (<b>F</b>).</p>
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26 pages, 5799 KiB  
Review
Exploring the Benzazoles Derivatives as Pharmacophores for AChE, BACE1, and as Anti-Aβ Aggregation to Find Multitarget Compounds against Alzheimer’s Disease
by Martha Cecilia Rosales Hernández, Marycruz Olvera-Valdez, Jazziel Velazquez Toledano, Jessica Elena Mendieta Wejebe, Leticia Guadalupe Fragoso Morales and Alejandro Cruz
Molecules 2024, 29(19), 4780; https://doi.org/10.3390/molecules29194780 - 9 Oct 2024
Viewed by 1168
Abstract
Despite the great effort that has gone into developing new molecules as multitarget compounds to treat Alzheimer’s disease (AD), none of these have been approved to treat this disease. Therefore, it will be interesting to determine whether benzazoles such as benzimidazole, benzoxazole, and [...] Read more.
Despite the great effort that has gone into developing new molecules as multitarget compounds to treat Alzheimer’s disease (AD), none of these have been approved to treat this disease. Therefore, it will be interesting to determine whether benzazoles such as benzimidazole, benzoxazole, and benzothiazole, employed as pharmacophores, could act as multitarget drugs. AD is a multifactorial disease in which several pharmacological targets have been identified—some are involved with amyloid beta (Aβ) production, such as beta secretase (BACE1) and beta amyloid aggregation, while others are involved with the cholinergic system as acetylcholinesterase (AChE) and butirylcholinesterase (BChE) and nicotinic and muscarinic receptors, as well as the hyperphosphorylation of microtubule-associated protein (tau). In this review, we describe the in silico and in vitro evaluation of benzazoles on three important targets in AD: AChE, BACE1, and Aβ. Benzothiazoles and benzimidazoles could be the best benzazoles to act as multitarget drugs for AD because they have been widely evaluated as AChE inhibitors, forming π–π interactions with W286, W86, Y72, and F338, as well as in the AChE gorge and catalytic site. In addition, the sulfur atom from benzothiazol interacts with S286 and the aromatic ring from W84, with these compounds having an IC50 value in the μM range. Also, benzimidazoles and benzothiazoles can inhibit Aβ aggregation. However, even though benzazoles have not been widely evaluated on BACE1, benzimidazoles evaluated in vitro showed an IC50 value in the nM range. Therefore, important chemical modifications could be considered to improve multitarget benzazoles’ activity, such as substitutions in the aromatic ring with electron withdrawal at position five, or a linker 3 or 4 carbons in length, which would allow for better interaction with targets. Full article
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Figure 1
<p>Chemical structures of benzazoles. Benzothiazole (<b>a</b>), riluzole (<b>b</b>), thiourea (<b>c</b>), urea (<b>d</b>), dexpramipexole (<b>e</b>), and pramipexole (<b>f</b>). Derivative compounds from riluzole with tioguanidines compound <b>3b</b> (<b>g</b>) and compound <b>3d</b> (<b>h</b>); benzimidazole (<b>i</b>) and benzoxazole (<b>j</b>).</p>
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<p>Chemical structures of benzoxazole derivatives used as AChE and BChE inhibitors. Compounds <b>11</b> (<b>a</b>) [<a href="#B46-molecules-29-04780" class="html-bibr">46</a>], <b>3g</b> (<b>b</b>) [<a href="#B47-molecules-29-04780" class="html-bibr">47</a>], <b>34</b> (<b>c</b>) [<a href="#B48-molecules-29-04780" class="html-bibr">48</a>], <b>5f</b> (<b>d</b>) [<a href="#B49-molecules-29-04780" class="html-bibr">49</a>], <b>32a</b> (<b>e</b>) [<a href="#B50-molecules-29-04780" class="html-bibr">50</a>], <b>33</b> (<b>f</b>) [<a href="#B50-molecules-29-04780" class="html-bibr">50</a>], <b>1g</b> (<b>g</b>) [<a href="#B51-molecules-29-04780" class="html-bibr">51</a>], <b>1a</b> (<b>h</b>) [<a href="#B51-molecules-29-04780" class="html-bibr">51</a>], and <b>1d</b> (<b>i</b>) [<a href="#B51-molecules-29-04780" class="html-bibr">51</a>].</p>
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<p>Chemical structures of benzothiazole compounds used as AChE inhibitors. Compounds <b>10w</b> (<b>a</b>) [<a href="#B53-molecules-29-04780" class="html-bibr">53</a>], <b>7a</b> (<b>b</b>), <b>7b</b> (<b>c</b>), <b>7c</b> (<b>d</b>), <b>7d</b> (<b>e</b>), <b>7e</b> (<b>f</b>) [<a href="#B54-molecules-29-04780" class="html-bibr">54</a>], <b>A5</b> (<b>g</b>), <b>A13</b> (<b>h</b>) [<a href="#B55-molecules-29-04780" class="html-bibr">55</a>], and <b>BPCT</b> (<b>i</b>) [<a href="#B56-molecules-29-04780" class="html-bibr">56</a>].</p>
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<p>Chemical structures of compounds <b>3d</b> (<b>a</b>), <b>3h</b> (<b>b</b>) [<a href="#B61-molecules-29-04780" class="html-bibr">61</a>], <b>2e</b> (<b>c</b>), <b>3c</b> (<b>d</b>), <b>3e</b> (<b>e</b>) [<a href="#B62-molecules-29-04780" class="html-bibr">62</a>], <b>5IIc</b> (<b>f</b>) [<a href="#B63-molecules-29-04780" class="html-bibr">63</a>], <b>4b</b> (<b>g</b>) [<a href="#B64-molecules-29-04780" class="html-bibr">64</a>], <b>7e</b> (<b>h</b>), and of donepezil (<b>i</b>) [<a href="#B65-molecules-29-04780" class="html-bibr">65</a>].</p>
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<p>Chemical structures of compounds <b>A12</b> (<b>a</b>) [<a href="#B67-molecules-29-04780" class="html-bibr">67</a>], <b>A1</b> (<b>b</b>), <b>A2</b> (<b>c</b>), <b>A3</b> (<b>d</b>), <b>A4</b> (<b>e</b>) [<a href="#B68-molecules-29-04780" class="html-bibr">68</a>], <b>16</b> (<b>f</b>), <b>21</b> (<b>g</b>) [<a href="#B69-molecules-29-04780" class="html-bibr">69</a>], <b>11</b> (<b>h</b>) [<a href="#B70-molecules-29-04780" class="html-bibr">70</a>], <b>12d</b> (<b>i</b>), and <b>12k</b> (<b>j</b>) [<a href="#B71-molecules-29-04780" class="html-bibr">71</a>].</p>
Full article ">Figure 6
<p>Chemical structures of compounds <b>1b</b> (<b>a</b>), <b>1c</b> (<b>b</b>), <b>1g</b> (<b>c</b>), <b>2c</b> (<b>d</b>), <b>2e</b> (<b>e</b>), <b>2h</b> (<b>f</b>) [<a href="#B72-molecules-29-04780" class="html-bibr">72</a>], <b>15g</b> (<b>g</b>), <b>15b</b> (<b>h</b>) [<a href="#B73-molecules-29-04780" class="html-bibr">73</a>], <b>12</b> (<b>i</b>), and <b>13</b> (<b>j</b>) [<a href="#B74-molecules-29-04780" class="html-bibr">74</a>].</p>
Full article ">Figure 7
<p>Chemical structures of compounds <b>5</b> (<b>a</b>) [<a href="#B75-molecules-29-04780" class="html-bibr">75</a>], <b>11</b> (<b>b</b>), <b>14</b> (<b>c</b>) [<a href="#B76-molecules-29-04780" class="html-bibr">76</a>], <b>34</b> (<b>d</b>) [<a href="#B77-molecules-29-04780" class="html-bibr">77</a>], and <b>7c</b> (<b>e</b>) [<a href="#B78-molecules-29-04780" class="html-bibr">78</a>].</p>
Full article ">Figure 8
<p>Principal targets to be inhibited by benzazoles as possible multitarget drugs for the treatment of AD. Each row indicated the enzyme or peptide that it inhibited for each benzazole. R<sup>1</sup> indicated the substitution in the benzazole ring in the 2 position. Figure created with <a href="http://BioRender.com" target="_blank">BioRender.com</a>.</p>
Full article ">Figure 9
<p>Compound <b>4f</b> (<b>a</b>) [<a href="#B93-molecules-29-04780" class="html-bibr">93</a>], compound <b>3d</b> (<b>b</b>) [<a href="#B95-molecules-29-04780" class="html-bibr">95</a>], compound <b>TAC-BIM1</b> (<b>c</b>), compound <b>TAC-BIM2</b> (<b>d</b>) [<a href="#B96-molecules-29-04780" class="html-bibr">96</a>], compound <b>4c</b> (<b>e</b>) and compound <b>4g</b> (<b>f</b>) [<a href="#B97-molecules-29-04780" class="html-bibr">97</a>].</p>
Full article ">
12 pages, 4667 KiB  
Article
Multistimuli Luminescence and Anthelmintic Activity of Zn(II) Complexes Based on 1H-Benzimidazole-2-yl Hydrazone Ligands
by Alexey Gusev, Elena Braga, Alexandr Kaleukh, Michail Baevsky, Mikhail Kiskin and Wolfgang Linert
Inorganics 2024, 12(9), 256; https://doi.org/10.3390/inorganics12090256 - 23 Sep 2024
Viewed by 581
Abstract
Three novel Zn(II) mononuclear complexes with the general formula ZnL2Cl2 (L = 2-(4-R-phenylmethylene)benzimidazol-2-hydrazines; R-H (1), R-CH3 (2), and R-OCH3 (3)) were synthesized and fully characterized by various means. These complexes demonstrate excitation-dependent emission, which is detected by a [...] Read more.
Three novel Zn(II) mononuclear complexes with the general formula ZnL2Cl2 (L = 2-(4-R-phenylmethylene)benzimidazol-2-hydrazines; R-H (1), R-CH3 (2), and R-OCH3 (3)) were synthesized and fully characterized by various means. These complexes demonstrate excitation-dependent emission, which is detected by a change in the emission color (from blue to green) upon an increase in the excitation wavelength. Moreover complex 1 shows reversible mechanochromic luminescence behavior due to the reversible loss of solvated methanol molecules upon the intense grinding of crystals. In addition, 1 exhibits vapochromic properties, which originate from the adsorption methanol vapor on the crystal surface. The strengthening of anthelmintic activity at the transition from free hydrazones to zinc-based complexes is shown. Full article
(This article belongs to the Section Coordination Chemistry)
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Figure 1

Figure 1
<p>Crystal and molecular structures of 1 (<b>a</b>), 2 (<b>c</b>), and 3 (<b>d</b>). Solvate molecules are omitted for clarity. Fragment of supramolecular architecture of 1 (<b>b</b>) (Colour of the atoms: grey—C; red—O; green—Cl; blue—Zn; deep blue—N).</p>
Full article ">Figure 2
<p>(<b>a</b>) Emission spectra of as-prepared crystals of 1 at different excitation. (<b>b</b>) Emission spectra of 1 after treatment of CH<sub>3</sub>OH vapor at different excitation. (<b>c</b>) Emission spectra of 1 after grinding (exc. at 430 nm) (inset emission excited at 365 nm). (<b>d</b>) Image of as-prepared crystals after treatment and after grinding under UV lamp. (<b>e</b>) Emission spectra of as-prepared crystals of 2 at different excitation. (<b>f</b>) Emission spectra of as-prepared crystals of 3 at different excitation.</p>
Full article ">Figure 2 Cont.
<p>(<b>a</b>) Emission spectra of as-prepared crystals of 1 at different excitation. (<b>b</b>) Emission spectra of 1 after treatment of CH<sub>3</sub>OH vapor at different excitation. (<b>c</b>) Emission spectra of 1 after grinding (exc. at 430 nm) (inset emission excited at 365 nm). (<b>d</b>) Image of as-prepared crystals after treatment and after grinding under UV lamp. (<b>e</b>) Emission spectra of as-prepared crystals of 2 at different excitation. (<b>f</b>) Emission spectra of as-prepared crystals of 3 at different excitation.</p>
Full article ">Figure 3
<p>Optimized geometries of chemical structures of complexes 1–3.</p>
Full article ">Figure 4
<p>HOMO and LUMO orbitals of all molecules. <span class="html-italic">(pink and purple colours means positive and negative sign of wave function).</span></p>
Full article ">Scheme 1
<p>Ligands L1–L3 used in this study.</p>
Full article ">Scheme 2
<p>Synthesis of the Zn complexes with L1–L3.</p>
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15 pages, 1610 KiB  
Article
Linear and Angular Heteroannulated Pyridines Tethered 6-Hydroxy-4,7-Dimethoxybenzofuran: Synthesis and Antimicrobial Activity
by Najla A. Alshaye, Al-Shimaa Badran and Magdy A. Ibrahim
Molecules 2024, 29(18), 4496; https://doi.org/10.3390/molecules29184496 - 22 Sep 2024
Viewed by 587
Abstract
2-Chloropyridine-3-carbonitrile derivative 1 was utilized as a key precursor to build a series of linear and angular annulated pyridines linked to a 6-hydroxy-4,7-dimethoxybenzofuran moiety. Reaction of substrate 1 with various hydrazines afforded pyrazolo[3,4-b]pyridines. Treatment of substrate 1 with 1,3-N, [...] Read more.
2-Chloropyridine-3-carbonitrile derivative 1 was utilized as a key precursor to build a series of linear and angular annulated pyridines linked to a 6-hydroxy-4,7-dimethoxybenzofuran moiety. Reaction of substrate 1 with various hydrazines afforded pyrazolo[3,4-b]pyridines. Treatment of substrate 1 with 1,3-N,N-binucleophiles including 3-amino-1,2,4-triazole, 5-amino-1H-tetrazole, 3-amino-6-methyl-1,2,4-triazin-5(4H)-one and 2-aminobenzimidazole produced the novel angular pyrido[3,2-e][1,2,4]triazolo[4,3-a]pyrimidine, pyrido[3,2-e][1,2,4]tetrazolo[1,5-a]pyrimidine, pyrido[3′,2′:5,6] pyrimido[2,1-c][1,2,4]triazine and benzo[4,5]imidazo[1,2-a]pyrido[3,2-e]pyrimidine, respectively. Reaction of substrate 1 with 1,3-C,N-binucleophiles including cyanoacetamides and 1H-benzimidazol-2-ylacetonitrile furnished 1,8-naphthyridines and benzoimidazonaphthyridine. Moreover, reacting substrate 1 with 5-aminopyrazoles gave pyrazolo[3,4-b][1,8]naphthyridines. Finally, reaction of compound 1 with 6-aminouracils as cyclic enamines yielded pyrimido[4,5-b][1,8]naphthyridines. Some of the synthesized products showed noteworthy antimicrobial efficiency against all types of microbial strains. Structures of the produced compounds were established using analytical and spectroscopic tools. Full article
(This article belongs to the Special Issue Synthetic Studies Aimed at Heterocyclic Organic Compounds)
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Graphical abstract

Graphical abstract
Full article ">Chart 1
<p>The antibacterial efficiency of synthesized compounds against <span class="html-italic">S. aureus</span>.</p>
Full article ">Scheme 1
<p>Formation of pyrazolo[3,4-<span class="html-italic">b</span>]pyridines <b>4</b> and <b>5</b>.</p>
Full article ">Scheme 2
<p>Formation of pyridotriazolopyrimidine <b>6</b> and pyridotetrazolopyrimidine <b>7</b>.</p>
Full article ">Scheme 3
<p>Formation of angular pyridopyrimidotriazine <b>9</b> and benzoimidazopyrido-pyrimidine <b>10</b>.</p>
Full article ">Scheme 4
<p>Formation of naphthyridines <b>11</b>, <b>12</b> and benzoimidazonaphthyridine <b>13</b>.</p>
Full article ">Scheme 5
<p>Formation of pyrazolo[3,4-<span class="html-italic">b</span>][1,8]naphthyridines <b>14</b> and <b>15</b>.</p>
Full article ">Scheme 6
<p>Formation of pyrimido[4,5-<span class="html-italic">b</span>][1,8]naphthyridines <b>16</b>–<b>18</b>.</p>
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55 pages, 49774 KiB  
Review
Structural Rheology in the Development and Study of Complex Polymer Materials
by Sergey O. Ilyin
Polymers 2024, 16(17), 2458; https://doi.org/10.3390/polym16172458 - 29 Aug 2024
Cited by 2 | Viewed by 1172
Abstract
The progress in polymer science and nanotechnology yields new colloidal and macromolecular objects and their combinations, which can be defined as complex polymer materials. The complexity may include a complicated composition and architecture of macromolecular chains, specific intermolecular interactions, an unusual phase behavior, [...] Read more.
The progress in polymer science and nanotechnology yields new colloidal and macromolecular objects and their combinations, which can be defined as complex polymer materials. The complexity may include a complicated composition and architecture of macromolecular chains, specific intermolecular interactions, an unusual phase behavior, and a structure of a multi-component polymer-containing material. Determination of a relation between the structure of a complex material, the structure and properties of its constituent elements, and the rheological properties of the material as a whole is the subject of structural rheology—a valuable tool for the development and study of novel materials. This work summarizes the author’s structural–rheological studies of complex polymer materials for determining the conditions and rheo-manifestations of their micro- and nanostructuring. The complicated chemical composition of macromolecular chains and its role in polymer structuring via block segregation and cooperative hydrogen bonds in melt and solutions is considered using tri- and multiblock styrene/isoprene and vinyl acetate/vinyl alcohol copolymers. Specific molecular interactions are analyzed in solutions of cellulose; its acetate butyrate; a gelatin/carrageenan combination; and different acrylonitrile, oxadiazole, and benzimidazole copolymers. A homogeneous structuring may result from a conformational transition, a mesophase formation, or a macromolecular association caused by a complex chain composition or specific inter- and supramolecular interactions, which, however, may be masked by macromolecular entanglements when determining a rheological behavior. A heterogeneous structure formation implies a microscopic phase separation upon non-solvent addition, temperature change, or intense shear up to a macroscopic decomposition. Specific polymer/particle interactions have been examined using polyethylene oxide solutions, polyisobutylene melts, and cellulose gels containing solid particles of different nature, demonstrating the competition of macromolecular entanglements, interparticle interactions, and adsorption polymer/particle bonds in governing the rheological properties. Complex chain architecture has been considered using long-chain branched polybutylene-adipate-terephthalate and polyethylene melts, cross-linked sodium hyaluronate hydrogels, asphaltene solutions, and linear/highly-branched polydimethylsiloxane blends, showing that branching raises the viscosity and elasticity and can result in limited miscibility with linear isomonomer chains. Finally, some examples of composite adhesives, membranes, and greases as structured polymeric functional materials have been presented with the demonstration of the relation between their rheological and performance properties. Full article
(This article belongs to the Special Issue Rheology and Processing of Polymer Materials)
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Figure 1

Figure 1
<p>Objects of the study.</p>
Full article ">Figure 2
<p>A generalized flow diagram of materials characterized by Newtonian behavior (<span class="html-italic">1</span>), pseudoplasticity (shear-thinning) typical for polymer melts/concentrated solutions (<span class="html-italic">2</span>) and colloid dispersions (<span class="html-italic">2</span>′), viscoplasticity of non-flowable strong gels (<span class="html-italic">3</span>) and prone-to-creep soft gels (<span class="html-italic">3</span>′), or dilatancy (shear-thickening) (<span class="html-italic">4</span>). The diagram’s right side shows the viscosity ranges inherent to volatile polymer solvents (<span class="html-italic">I</span>); easily flowing liquids such as base oils, plasticizers, and dilute polymer solutions (<span class="html-italic">II</span>); moderately flowing liquids, including oligomers and concentrated polymer solutions (<span class="html-italic">III</span>); poorly flowing liquids such as polymer melts (<span class="html-italic">IV</span>); and systems in a rubbery or glass-like state (<span class="html-italic">V</span>). The top side indicates viscosity drop zones due to the reduction in density of weak van der Waals and supramolecular interactions (<span class="html-italic">a</span>), stronger intermolecular hydrogen bonds and interparticle coagulation contacts (<span class="html-italic">b</span>), and interparticle phase contacts and macromolecular entanglements (<span class="html-italic">c</span>).</p>
Full article ">Figure 3
<p>Frequency dependencies of storage modulus (<span class="html-italic">G</span>′, solid lines) and loss modulus (<span class="html-italic">G</span>″, dashed lines) of materials showing the behavior of Maxwell viscoelastic liquid (<span class="html-italic">1</span>); Kelvin–Voigt elastoviscous solid (<span class="html-italic">2</span>); solid-like gel (<span class="html-italic">3</span>); or a monodisperse polymer having three relaxation states (<span class="html-italic">4</span>): viscous (zone <span class="html-italic">I</span>, curves are the same as shown for <span class="html-italic">1</span>), rubbery (<span class="html-italic">II</span>), and glassy (<span class="html-italic">III</span>). Thus, polymer systems have one more relaxation state due to macromolecular entanglements. The inset shows the moduli’s slopes according to the Maxwell model in the terminal (low-frequency) zone. Potentially, any system is liquid-like at low frequencies of external actions (long observation times) and conversely becomes solid-like with an increase in the frequency, as reflected by the Deborah number—the ratio of the relaxation time to the time of the applied action or its observation <span class="html-italic">De</span> = <span class="html-italic">τ/t</span> [<a href="#B76-polymers-16-02458" class="html-bibr">76</a>,<a href="#B77-polymers-16-02458" class="html-bibr">77</a>].</p>
Full article ">Figure 4
<p>Normalized responses of polyethylene melt (<span class="html-italic">σ</span>/<span class="html-italic">σ</span><sub>0</sub>) to a linear input action, the periodic deformation (<span class="html-italic">γ</span>), according to a harmonic law with different strain amplitudes (<span class="html-italic">γ</span><sub>0</sub>) indicated near the curves (adapted from [<a href="#B91-polymers-16-02458" class="html-bibr">91</a>]).</p>
Full article ">Figure 5
<p>Lissajous figures with linear ((<b>a</b>), <span class="html-italic">γ</span><sub>0</sub> = 100%) and nonlinear ((<b>b</b>), <span class="html-italic">γ</span><sub>0</sub> = 1000%) responses of polyethylene melt (adapted from [<a href="#B91-polymers-16-02458" class="html-bibr">91</a>]).</p>
Full article ">Figure 6
<p>Amplitude dependencies of storage modulus (<span class="html-italic">G</span>′, solid lines) and loss modulus (<span class="html-italic">G</span>″, dashed lines) for Maxwell’s (<span class="html-italic">1</span>), viscoplastic (<span class="html-italic">2</span>), and dilatant (<span class="html-italic">3</span>) media. The vertical dashed lines represent the limit of the linear viscoelasticity region for different systems (<span class="html-italic">γ</span><sub>0</sub> where <span class="html-italic">G</span>′(<span class="html-italic">γ</span><sub>0</sub>) ≠ <span class="html-italic">const</span>): smaller for structured colloids and longer for homogeneous polymeric and glass-forming liquids.</p>
Full article ">Figure 7
<p>Storage and loss moduli versus angular frequency (<b>a</b>) and viscosity versus shear stress (<b>b</b>) at 170 °C: polyisoprene (<span class="html-italic">1</span>; 65 kDa), polystyrene (<span class="html-italic">5</span>; 184 kDa), and SIS containing 13 (<span class="html-italic">2</span>; 144 kDa, 12 nm), 18 (<span class="html-italic">3</span>; 140 kDa, 10 nm), or 44 wt% of styrene units (<span class="html-italic">4</span>; 82 kDa, 5 nm). The values in parentheses represent the number-average molecular weight (<span class="html-italic">M</span><sub>n</sub>) and diameter or thickness of polystyrene domains (according to [<a href="#B103-polymers-16-02458" class="html-bibr">103</a>]). Schematic SIS microstructures are in the middle.</p>
Full article ">Figure 8
<p>Frequency dependencies of storage and loss moduli measured at different temperatures and normalized to 120 °C for random (<b>a</b>) and multiblock (<b>b</b>) vinyl acetate/vinyl alcohol equimolar copolymers having polymerization degrees of 450. Viscoelastic regions represent terminal zone (I), rubbery plateau (II), glass transition (III), and glassy state (IV). The time–temperature superposition principle works well since the curves overlap (<b>a</b>), and vice versa (<b>b</b>). Insets show schematically intermolecular hydrogen bonds—simultaneously intra- and inter-chain (<b>a</b>) and predominantly inter-chain cooperative (<b>b</b>) (adapted from [<a href="#B104-polymers-16-02458" class="html-bibr">104</a>,<a href="#B105-polymers-16-02458" class="html-bibr">105</a>]).</p>
Full article ">Figure 9
<p>Concentration dependencies of the reduced viscosity of vinyl acetate/vinyl alcohol equimolar copolymers in DMF at 20 °C in the coordinates of the Huggins and Kraemer equations (<b>a</b>) and the size distribution of copolymer macromolecules and their associates by light scattering intensity in the solutions with copolymer concentrations of 0.28 g/dL (<b>b</b>) (adapted from [<a href="#B105-polymers-16-02458" class="html-bibr">105</a>]). The reduced viscosity for the random copolymer decreases with dilution (<b>a</b>), as for a usual polymer in its solution, whereas it goes through a minimum for the multiblock copolymer and then increases because of the growing size of the macromolecular associates, which are less likely to break down through mutual hydrodynamic action when their concentration becomes lower. The macromolecular association of the multiblock copolymer appears evident from the much larger sizes of its diffusing formations (<b>b</b>) consisting of dozens of individual chains.</p>
Full article ">Figure 10
<p>Interchain interactions of random (<b>a</b>) and multiblock (<b>b</b>) vinyl acetate/vinyl alcohol copolymers in <span class="html-italic">N</span>,<span class="html-italic">N</span>-dimethylformamide (adapted from [<a href="#B105-polymers-16-02458" class="html-bibr">105</a>]).</p>
Full article ">Figure 11
<p>Temperature dependencies of viscosity for 5% solutions of equimolar vinyl acetate/vinyl alcohol copolymers in DMF at 100 s<sup>−1</sup> (<b>a</b>) (the inset shows dependencies of viscosity on shear stress for these solutions at −20 °C) and shear stress dependencies of viscosity for 10% solutions of the same copolymers in DMF at 20 °C (<b>b</b>) (adapted from [<a href="#B105-polymers-16-02458" class="html-bibr">105</a>]). The viscosity of the random copolymer in its semi-dilute solution increases smoothly upon cooling, like for a usual polymer (<b>a</b>). In contrast, the viscosity rises in a jump-like manner for the multiblock copolymer because of the transition of its solution to the gel state, i.e., the arising of a yield stress of substantial value compared to the negligibly low yield stress of the weakly structured solution of the random copolymer (<span class="html-italic">σ</span><sub>Y</sub> of 19 Pa vs. of 0.012 Pa at −20 °C, see the inset). The transition to concentrated solutions (<b>b</b>) makes multiblock macromolecules metastable—non-flowable at low shear stresses and phase-separable at high ones, unlike the random copolymer having a nearly constant viscosity in the solution.</p>
Full article ">Figure 12
<p>Shear stress dependencies of viscosity (<b>a</b>,<b>b</b>) and frequency dependencies of storage and loss moduli (<b>c</b>,<b>d</b>) for solutions of acrylonitrile homo- (<b>a</b>,<b>c</b>) and terpolymer (<b>b</b>,<b>d</b>) in DMSO at 20 °C. The polymer mass fraction is indicated at the curves or in the legend (adapted from [<a href="#B120-polymers-16-02458" class="html-bibr">120</a>,<a href="#B121-polymers-16-02458" class="html-bibr">121</a>]). The homopolymer in its solution exhibits non-Newtonian behavior only at high shear stresses and high concentrations (<b>a</b>), like an ordinary polymer, also showing the usual Maxwell viscoelasticity (<b>c</b>). In contrast, the terpolymer in solution changes behavior from the standard pseudoplasticity of a concentrated polymer solution to anomalous viscoplasticity typical for gels when its content declines (<b>b</b>), just as its viscoelasticity transforms from a Maxwellian liquid to a gel-like state upon dilution (<b>d</b>).</p>
Full article ">Figure 12 Cont.
<p>Shear stress dependencies of viscosity (<b>a</b>,<b>b</b>) and frequency dependencies of storage and loss moduli (<b>c</b>,<b>d</b>) for solutions of acrylonitrile homo- (<b>a</b>,<b>c</b>) and terpolymer (<b>b</b>,<b>d</b>) in DMSO at 20 °C. The polymer mass fraction is indicated at the curves or in the legend (adapted from [<a href="#B120-polymers-16-02458" class="html-bibr">120</a>,<a href="#B121-polymers-16-02458" class="html-bibr">121</a>]). The homopolymer in its solution exhibits non-Newtonian behavior only at high shear stresses and high concentrations (<b>a</b>), like an ordinary polymer, also showing the usual Maxwell viscoelasticity (<b>c</b>). In contrast, the terpolymer in solution changes behavior from the standard pseudoplasticity of a concentrated polymer solution to anomalous viscoplasticity typical for gels when its content declines (<b>b</b>), just as its viscoelasticity transforms from a Maxwellian liquid to a gel-like state upon dilution (<b>d</b>).</p>
Full article ">Figure 13
<p>Interactions between acrylonitrile/sodium itaconate copolymer macromolecules in anhydrous DMSO (<b>a</b>) or the same solution in the presence of water (<b>b</b>) (adapted from [<a href="#B121-polymers-16-02458" class="html-bibr">121</a>]).</p>
Full article ">Figure 14
<p>Viscosity vs. shear stress (<b>a</b>) and storage and loss moduli vs. angular frequency (<b>b</b>) for 18% solutions of acrylonitrile terpolymer in water-containing DMSO at 20 °C. The legends indicate the water mass fraction in the solutions (adapted from [<a href="#B120-polymers-16-02458" class="html-bibr">120</a>,<a href="#B121-polymers-16-02458" class="html-bibr">121</a>]).</p>
Full article ">Figure 15
<p>Steady-state viscosity and complex viscosity (<b>a</b>) at 20 °C as functions of shear rate and angular frequency, respectively, and the storage modulus (<b>b</b>) as a function of temperature during heating or cooling (directions indicated by arrows) for solutions of the acrylonitrile terpolymer in DMSO. The terpolymer mass fraction and water presence are near the curves (adapted from [<a href="#B120-polymers-16-02458" class="html-bibr">120</a>,<a href="#B121-polymers-16-02458" class="html-bibr">121</a>]).</p>
Full article ">Figure 16
<p>Thermograms of acrylonitrile terpolymer (PAN) and its 5% solutions in DMSO with different water mass fractions (<b>a</b>) and optical transparency of these solutions compared to DMSO at 20 °C (<b>b</b>) (adapted from [<a href="#B99-polymers-16-02458" class="html-bibr">99</a>,<a href="#B120-polymers-16-02458" class="html-bibr">120</a>]).</p>
Full article ">Figure 17
<p>Viscosity as a function of shear stress (<b>a</b>) and storage and loss moduli as functions of angular frequency (<b>b</b>) at 25 °C for 14% cellulose solutions in [EMIM]Ac containing DMSO whose mass fraction in the solvent is near the curves or in the legend (adapted from [<a href="#B130-polymers-16-02458" class="html-bibr">130</a>]).</p>
Full article ">Figure 18
<p>Viscosity vs. shear stress (<b>a</b>) and storage and loss moduli vs. angular frequency (<b>b</b>) for 14% cellulose solutions at 25 °C in [EMIM]Ac containing water whose mass fraction is near the curves or in the legend (adapted from [<a href="#B130-polymers-16-02458" class="html-bibr">130</a>]).</p>
Full article ">Figure 19
<p>Synthesis scheme for sodium salts of poly(1,3,4-oxadiazole-2,5-diyl-3-sulfo-1,4-phenyleneoxy-2-sulfo-1,4-phenylene) (P0), poly(1,3,4-oxadiazole-2,5-diyl-6-sulfo-10,10-dioxophenoxathiine-2,8-diyl) (P100), and their copolymers (P25, P50, and P75).</p>
Full article ">Figure 20
<p>Viscosity as a function of shear stress (<b>a</b>) and storage and loss moduli as functions of angular frequency (<b>b</b>) for solutions of oxadiazole copolymers in an equivolume DMSO/FA mixture at 25 °C. Copolymers P0 and P25 are insoluble (adapted from [<a href="#B137-polymers-16-02458" class="html-bibr">137</a>]).</p>
Full article ">Figure 21
<p>Specific viscosity of oxadiazole copolymers in an equivolume mixture of DMSO/FA (<b>a</b>) or DMSO/FA/water (<b>b</b>) at 25 °C. The insets show microphotographs of mesophases in crossed polarizers (3.5× magnification) (adapted from [<a href="#B137-polymers-16-02458" class="html-bibr">137</a>]).</p>
Full article ">Figure 22
<p>Viscosity as a function of shear stress (<b>a</b>) and storage and loss moduli as functions of angular frequency (<b>b</b>) for polyoxadiazole solutions in an equivolume DMSO/FA/water mixture at 25 °C (adapted from [<a href="#B137-polymers-16-02458" class="html-bibr">137</a>]).</p>
Full article ">Figure 23
<p>Storage modulus vs. temperature at an angular frequency of 6.28 rad/s (<b>a</b>) and viscosity vs. shear stress at 14 °C (<b>b</b>) for gelatin hydrogels (100 kDa, 1 wt%) containing <span class="html-italic">κ</span>-carrageenan (680 kDa), whose mass fraction is in the legends (adapted from [<a href="#B145-polymers-16-02458" class="html-bibr">145</a>]).</p>
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<p>Storage and loss moduli versus angular frequency for gelatin, <span class="html-italic">κ</span>-carrageenan, and their combined hydrogels at 14 °C (<b>a</b>) and the transformation of intermolecular interactions of gelatin macromolecules in the presence of <span class="html-italic">κ</span>-carrageenan with an example of glycine and hydroxyproline units (<b>b</b>). Dashed lines represent hydrogen, ion–dipole, and ionic bonds (adapted from [<a href="#B145-polymers-16-02458" class="html-bibr">145</a>]).</p>
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<p>Viscosity versus temperature at a shear rate of 10 s<sup>−1</sup> (<b>a</b>) or versus shear stress at 25 °C (<b>b</b>) for acetyl tributyl citrate (ATBC) containing cellulose acetobutyrate (CAB), whose mass fraction is near the curves (adapted from [<a href="#B146-polymers-16-02458" class="html-bibr">146</a>]). The viscosity of the pure ATBC grows smoothly upon cooling, whereas the viscosity of the CAB/ATBC solution rises in a step-like manner at 55 °C because of gel formation (<b>a</b>) manifesting itself in a yield stress behavior, where the yield stress value becomes higher with an increase in the CAB mass fraction (<b>b</b>).</p>
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<p>Frequency dependencies of storage and loss moduli for CAB/ATBC gels of different compositions at 25 °C (<b>a</b>) and at different temperatures and a 10% CAB mass fraction (<b>b</b>) (adapted from [<a href="#B146-polymers-16-02458" class="html-bibr">146</a>]). Higher CAB content (<b>a</b>) and cooling (<b>b</b>) elevate gels’ stiffness, but only a temperature as low as −80 °C and high applied frequencies cause their notable mechanical glass transition, i.e., an increase in the moduli upon a rise in angular frequency, indicating a rubbery-like state of the gels at higher temperatures.</p>
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<p>Complex viscosity of a 5% solution of benzimidazole copolymer in DMA as a function of temperature at an angular frequency of 6.28 rad/s, a strain amplitude of 10%, and the heating rate indicated in °C/min near the curves (<b>a</b>), as well as the temperature of the phase separation of this solution as a function of the heating rate (<b>b</b>) (adapted from [<a href="#B100-polymers-16-02458" class="html-bibr">100</a>]).</p>
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<p>Viscosity of a 5% solution of benzimidazole copolymer in DMA as a function of temperature at a heating rate of 10 °C/min and a shear stress indicated in Pa near the curves (<b>a</b>), as well as the temperature of the phase separation of this solution as a function of the shear stress (<b>b</b>). The inset shows the increase in the phase separation temperature under shear action (adapted from [<a href="#B100-polymers-16-02458" class="html-bibr">100</a>]).</p>
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<p>Storage and loss moduli as functions of strain amplitude for a 20% solution of acrylonitrile terpolymer in DMSO at an angular frequency of 6.28 rad/s and 20 °C, as well as photographs of the solution after testing with strains of 1600% ((<b>a</b>), zone I of macromolecular orientation), 4000% ((<b>b</b>), zone II of phase separation), and 250,000% ((<b>c</b>,<b>d</b>), zone III of wall slip) (adapted from [<a href="#B99-polymers-16-02458" class="html-bibr">99</a>]).</p>
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<p>Viscosity as a function of shear stress (<b>a</b>) and storage and loss moduli as a function of angular frequency (<b>b</b>) for a 3 vol% dispersion of fumed silica (7 nm, 388 m<sup>2</sup>/g) in DMSO containing polyethylene oxide (40 kDa) whose mass fraction is indicated near the curves and in the legend. The SiO<sub>2</sub> dispersion and 0.1–10% PEO solutions do not demonstrate viscoelasticity separately. <span class="html-italic">T</span> = 50 °C, preventing crystallization of PEO. The inset shows a schematic change in the structure of the SiO<sub>2</sub> dispersion in the presence of PEO (adapted from [<a href="#B155-polymers-16-02458" class="html-bibr">155</a>]).</p>
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<p>Viscosity as a function of shear stress (<b>a</b>) and storage and loss moduli as a function of angular frequency (<b>b</b>) for a 1% aqueous solution of polyethylene oxide (3 MDa), a 15% aqueous dispersion of bentonite (75 µm, 58 m<sup>2</sup>/g), and their combination at 25 °C. The inset shows a schematic change in the structure of the bentonite dispersion in the presence of PEO (adapted from [<a href="#B156-polymers-16-02458" class="html-bibr">156</a>]).</p>
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<p>Viscosity as a function of shear stress at 25 °C for a 1% aqueous PEO solution containing different bentonite mass fractions (<b>a</b>) and a 15% aqueous bentonite dispersion containing different PEO mass fractions (<b>b</b>) in comparison with the initial bentonite-free PEO solutions (adapted from [<a href="#B156-polymers-16-02458" class="html-bibr">156</a>]).</p>
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<p>Viscosity versus the shear rate at 25 °C for 10% CAB/ATBC gels containing boron nitride (<b>a</b>), graphite (<b>b</b>), or PTFE (<b>c</b>) and a scheme of transforming the initial gel structure (<b>d</b>) with the formation of an additional particle network (<b>e</b>), destruction of the polymer network with the formation of a particle network (<b>f</b>), or the action of particles as inactive fillers (<b>g</b>) (adapted from [<a href="#B146-polymers-16-02458" class="html-bibr">146</a>]).</p>
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<p>Viscosity versus the shear rate at 25 °C for 10% CAB/ATBC gels containing boron nitride (<b>a</b>), graphite (<b>b</b>), or PTFE (<b>c</b>) and a scheme of transforming the initial gel structure (<b>d</b>) with the formation of an additional particle network (<b>e</b>), destruction of the polymer network with the formation of a particle network (<b>f</b>), or the action of particles as inactive fillers (<b>g</b>) (adapted from [<a href="#B146-polymers-16-02458" class="html-bibr">146</a>]).</p>
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<p>Viscosity versus shear stress (<b>a</b>) and storage and loss moduli versus angular frequency (<b>b</b>) at 20 °C for an adhesive mixture of poly(iso)butylenes (40% 4.5 kDa, 50% 51 kDa, and 10% 1.1 MDa) containing pyrogenic silica particles (20 nm, 175 m<sup>2</sup>/g) whose mass fraction is indicated near the curves or in the legend (adapted from [<a href="#B157-polymers-16-02458" class="html-bibr">157</a>]).</p>
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<p>Viscosity versus shear rate for 7% SiO<sub>2</sub> dispersions (7 nm, 388 m<sup>2</sup>/g) in PEO melts having different molecular weights (indicated near the curves) at 120 °C (<b>a</b>) and the relative viscosity of 3% SiO<sub>2</sub> dispersions in PEO (400 Da) at 20 °C versus particles’ specific surface area and size (<b>b</b>) (adapted from [<a href="#B162-polymers-16-02458" class="html-bibr">162</a>]).</p>
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<p>Schematic diagram of the rheological state for dispersions of particles in polymer media depending on their size and volume fraction and the polymer’s molecular weight (adapted from [<a href="#B162-polymers-16-02458" class="html-bibr">162</a>]).</p>
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<p>SEM images of (<b>a</b>) microfibrillated cellulose (MFC) and (<b>b</b>) regenerated cellulose (RC), (<b>c</b>) dependencies of storage and loss moduli on the angular frequency for their 3% hydro- and organogels, and (<b>d</b>) the viscosity curves of these gels (adapted from [<a href="#B168-polymers-16-02458" class="html-bibr">168</a>,<a href="#B169-polymers-16-02458" class="html-bibr">169</a>,<a href="#B170-polymers-16-02458" class="html-bibr">170</a>]).</p>
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<p>Yield stress of gels versus nanocellulose content (<b>a</b>) and temperature dependencies of viscosity for two organogels compared to pure TEC (<b>b</b>) (adapted from [<a href="#B168-polymers-16-02458" class="html-bibr">168</a>,<a href="#B169-polymers-16-02458" class="html-bibr">169</a>,<a href="#B170-polymers-16-02458" class="html-bibr">170</a>]).</p>
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<p>Structural formulas of PBAT and polyfunctional comonomers (<b>a</b>) and shear stress dependencies of the viscosity (<b>b</b>), the first normal stress difference (<b>b</b>), and the relative elasticity coefficient (<b>c</b>) for PBAT melts at 190 °C. The legends indicate the comonomers’ number (adapted from [<a href="#B176-polymers-16-02458" class="html-bibr">176</a>]).</p>
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<p>Structural formulas of pre-catalysts (<b>a</b>) and dependencies of storage and loss moduli at 150 °C on the angular frequency (<b>b</b>) and each other (<b>c</b>) for polyethylenes synthesized at 80 °C with the involvement of the specified pre-catalysts (adapted from [<a href="#B179-polymers-16-02458" class="html-bibr">179</a>]).</p>
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<p>Continuous relaxation spectra for PE melts at 150 °C (<b>a</b>) and their highest Newtonian viscosity versus GPC-measured molecular weight (<b>b</b>). The pre-catalysts and synthesis temperatures are indicated in the legend and near the experimental points. The arrows show long-time shoulders associated with long-chain branching. The dashed line reflects the calculated viscosity for linear PE (adapted from [<a href="#B179-polymers-16-02458" class="html-bibr">179</a>]).</p>
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<p>Viscosity versus shear stress for aqueous solutions of sodium hyaluronate at 25 °C (<b>a</b>) and its gels (<b>b</b>) obtained using BDDE (BDDE/SH = 1/90 wt/wt; 5 mol% disaccharide units contain cross-links) (adapted from [<a href="#B184-polymers-16-02458" class="html-bibr">184</a>,<a href="#B185-polymers-16-02458" class="html-bibr">185</a>]).</p>
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<p>Storage and loss moduli versus angular frequency for the solution of sodium hyaluronate and its two gels (<b>a</b>) and the concentration dependencies of their specific viscosity (<math display="inline"><semantics> <mrow> <mover accent="true"> <mrow> <mi>γ</mi> </mrow> <mo>˙</mo> </mover> </mrow> </semantics></math> = 0.001 s<sup>−1</sup>) and yield stress (<b>b</b>) (adapted from [<a href="#B184-polymers-16-02458" class="html-bibr">184</a>,<a href="#B185-polymers-16-02458" class="html-bibr">185</a>]). Captions near the concentration dependencies indicate their slopes. The inset demonstrates an example of sodium hyaluronate’s cross-linked microgels stained with toluidine blue (adapted from [<a href="#B186-polymers-16-02458" class="html-bibr">186</a>]).</p>
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<p>Phase diagrams for linear/highly-branched siloxane blends ((<b>a</b>), UCST is indicated near the curves) and their viscosity as a function of temperature at <span class="html-italic">M</span><sub>L</sub>/<span class="html-italic">M</span><sub>HB</sub> = 166/12 kDa/kDa ((<b>b</b>), the inset shows the viscosity versus shear stress at 20 °C). The legends indicate molecular weight ratios (<b>a</b>) and volume fraction of highly branched macromolecules (<b>b</b>) (adapted from [<a href="#B187-polymers-16-02458" class="html-bibr">187</a>,<a href="#B189-polymers-16-02458" class="html-bibr">189</a>]).</p>
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<p>Dependencies of the viscosity of linear/highly-branched siloxane blends on the temperature at <span class="html-italic">M</span><sub>L</sub>/<span class="html-italic">M</span><sub>HB</sub> = 166/7.2 kDa/kDa ((<b>a</b>); the inset shows the viscosity versus shear stress at 0 °C) and the calculations of the blend viscosity at the linear variations of the parameters indicated near the curves, the transition from linear macromolecules to highly branched ones, and 0 °C (<b>b</b>) (adapted from [<a href="#B189-polymers-16-02458" class="html-bibr">189</a>]).</p>
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<p>Generalized scheme of structure formation in macromolecular systems.</p>
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<p>The viscosity of the poly(iso)butylene-based pressure-sensitive adhesives as a function of the volume fraction of dispersed particles (<b>a</b>) and the increase in time to failure of adhesive bonds of these adhesives with steel as a function of their viscosity at 25 °C (<b>b</b>) (adapted from [<a href="#B157-polymers-16-02458" class="html-bibr">157</a>,<a href="#B202-polymers-16-02458" class="html-bibr">202</a>,<a href="#B203-polymers-16-02458" class="html-bibr">203</a>,<a href="#B204-polymers-16-02458" class="html-bibr">204</a>]).</p>
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<p>The specific viscosity for asphaltenes (<span class="html-italic">M</span><sub>w</sub> = 828 Da) dissolved in diisooctyl sebacate at 25 °C ((<b>a</b>); the inset shows the frequency dependencies of the storage and loss moduli of the solutions) and the viscosity at 120 °C for SIS melts (44% styrene units, 82 kDa) containing asphaltenes (<b>b</b>). The legends indicate asphaltene mass fractions (adapted from [<a href="#B211-polymers-16-02458" class="html-bibr">211</a>,<a href="#B219-polymers-16-02458" class="html-bibr">219</a>]).</p>
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<p>The loss tangent versus temperature for the asphaltene-containing SIS at <span class="html-italic">ω</span> = 6.28 rad/s (<b>a</b>) and the adhesion strength and apparent work of its adhesive bonds with a steel surface upon pull-off at 25 °C (<b>b</b>) (adapted from [<a href="#B219-polymers-16-02458" class="html-bibr">219</a>]). The dashed line represents the glass-transition temperature for pure SIS.</p>
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<p>Permeability of DMF and retention coefficient for a model pollutant (Remazol Brilliant Blue R, 626 g/mol) when using cellulose nanofiltration membranes ((<b>a</b>), the precipitant and solvent are on the abscissa scale) and the electrical conductivity of polyoxadiazole films versus their sulfonation degree and the type of cation (<b>b</b>) (adapted from [<a href="#B130-polymers-16-02458" class="html-bibr">130</a>,<a href="#B137-polymers-16-02458" class="html-bibr">137</a>]).</p>
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<p>Friction and wear coefficients when testing lubricating greases based on TEC and nanocellulose (<b>a</b>) or ATBC and cellulose acetate butyrate (<b>b</b>) at 25 °C and a contact pressure of 1910 MPa. The cellulose-based thickener mass fraction and the presence of solid particles are indicated on the abscissa scale. Data for Litol and SVEM greases are provided for comparison (adapted from [<a href="#B146-polymers-16-02458" class="html-bibr">146</a>,<a href="#B168-polymers-16-02458" class="html-bibr">168</a>,<a href="#B169-polymers-16-02458" class="html-bibr">169</a>,<a href="#B227-polymers-16-02458" class="html-bibr">227</a>]).</p>
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8 pages, 1286 KiB  
Communication
Synthesis of Diastereomeric 2,6-bis{[3-(2-Hydroxy-5-substitutedbenzyl)octahydro-1H-benzimidazol-1-yl]methyl}-4-substituted Phenols (R = Me, OMe) by Mannich-Type Tandem Reactions
by Diego Quiroga, Jaime Ríos-Motta and Augusto Rivera
Molbank 2024, 2024(3), M1876; https://doi.org/10.3390/M1876 - 28 Aug 2024
Viewed by 610
Abstract
The synthesis and characterization of two novel diastereomeric Mannich bases was carried out from the reaction of the cyclic aminal (2R,7R,11S,16S)-1,8,10,17-tetraazapentacyclo[8.8.1.1.8,170.2,70.11,16]icosane 1 and p-cresol 2a and 4-methoxyphenol 2b [...] Read more.
The synthesis and characterization of two novel diastereomeric Mannich bases was carried out from the reaction of the cyclic aminal (2R,7R,11S,16S)-1,8,10,17-tetraazapentacyclo[8.8.1.1.8,170.2,70.11,16]icosane 1 and p-cresol 2a and 4-methoxyphenol 2b in a water/dioxane mixture. The title compounds (4ab) are interesting because bearing two 3-(2-hydroxy-5-substitutedbenzyl)octahydro-1H-benzimidazol-1-yl]methyl} substituents joined to an arenol ring. The formation of these new Mannich bases in the reaction mixture can be explained by aminomethylation of previously reported di-Mannich base 2,2′-((hexahydro-1H-benzo[d]imidazole-1,3(2H)-diyl)bis(methylene))bis(4-substituentphenol) 3ab. NMR analysis demonstrated that compounds 4ab were formed as diastereomeric mixtures. Subsequent experiments revealed that at longer reaction times, the percentage yield of these new products increased considerably (yield percentages up to 22–27%), suggesting a nucleophilic competition between the p-substituted phenols and Mannich bases of type 3 for aminal 1. Full article
(This article belongs to the Section Organic Synthesis and Biosynthesis)
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Graphical abstract

Graphical abstract
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<p>Labeled chemical structures of the formed diastereoisomers for the title compounds <b>4a–b</b>.</p>
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<p>Two-dimensional nuclear magnetic resonance experiments of compound <b>4a</b>. (<b>a</b>) COSY, (<b>b</b>) HMQC, (<b>c</b>) HMBC, (<b>d</b>) schematic representation of the connectivity between resonances of <sup>1</sup>H and <sup>13</sup>C atoms in <b>4a</b>.</p>
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<p>Sequential synthesis of <b>4a–b</b>.</p>
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13 pages, 4738 KiB  
Article
A Benzimidazole-Based N-Heterocyclic Carbene Derivative Exhibits Potent Antiproliferative and Apoptotic Effects against Colorectal Cancer
by Sarah Al-Nasser, Maha Hamadien Abdulla, Noura Alhassan, Mansoor-Ali Vaali-Mohammed, Suliman Al-Omar, Naceur Hamdi, Yasser Elnakady, Sabine Matou-Nasri and Lamjed Mansour
Medicina 2024, 60(9), 1379; https://doi.org/10.3390/medicina60091379 - 23 Aug 2024
Viewed by 974
Abstract
Background and Objectives: Colorectal cancer (CRC) remains a major global health issue. Although chemotherapy is the first-line treatment, its effectiveness is limited due to drug resistance developed in CRC. To overcome resistance and improve the prognosis of CRC patients, investigating new therapeutic [...] Read more.
Background and Objectives: Colorectal cancer (CRC) remains a major global health issue. Although chemotherapy is the first-line treatment, its effectiveness is limited due to drug resistance developed in CRC. To overcome resistance and improve the prognosis of CRC patients, investigating new therapeutic approaches is necessary. Materials and Methods: Using human colorectal adenocarcinoma (HT29) and metastatic CRC (SW620) cell lines, the potential anticancer properties of a newly synthesized compound 1-(Isobutyl)-3-(4-methylbenzyl) benzimidazolium chloride (IMBZC) were evaluated by performing MTT cytotoxicity, cell migration, and colony formation assays, as well as by monitoring apoptosis-related protein and gene expression using Western blot and reverse transcription–quantitative polymerase chain reaction technologies. Results: Tested at various concentrations, the half-maximal inhibitory concentrations (IC50) of IMBZC on HT29 and SW620 cell growth were determined to be 22.13 µM (6.97 μg/mL) and 15.53 µM (4.89 μg/mL), respectively. IMBZC did not alter the cell growth of normal HEK293 cell lines. In addition, IMBZC inhibited cell migration and significantly decreased colony formation, suggesting its promising role in suppressing cancer metastasis. Mechanistic analyses revealed that IMBZC treatment increased the expression of pro-apoptotic proteins p53 and Bax, while decreasing the expression of anti-apoptotic proteins Bcl-2 and Bcl-xL, thus indicating the induction of apoptosis in IMBZC-treated CRC cells, compared to untreated cells. Additionally, the addition of IMBZC to conventional chemotherapeutic drugs (i.e., 5-fluorouracil, irinotecan, and oxaliplatin) resulted in an increase in the cytotoxic potential of the drugs. Conclusions: This study suggests that IMBZC has substantial anticancer effects against CRC cells through its ability to induce apoptosis, inhibit cancer cell migration and colony formation, and enhance the cytotoxic effects of conventional chemotherapeutic drugs. These findings indicate that IMBZC could be a promising chemotherapeutic drug for the treatment of CRC. Further research should be conducted using in vivo models to confirm the anti-CRC activities of IMBZC. Full article
(This article belongs to the Section Gastroenterology & Hepatology)
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Figure 1

Figure 1
<p>Chemical structure of 1-(Isobutyl)-3-(4-methylbenzyl) benzimidazolium chloride (IMBZC) (MW = 314.85 g/mol).</p>
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<p>Assessment of the cytotoxic potential of compound IMBZC on colon adenocarcinoma HT29 and mCRC SW620 cells, in comparison with normal HEK293 cells, using MTT assay. Determination of percent viability of (<b>A</b>) HT29, (<b>B</b>) SW620, and (<b>C</b>) HEK923 cells after 24 h of incubation in the absence (i.e., control) or presence of increasing concentrations of (3.97 to 31.76 µM) IMBZC. * <span class="html-italic">p</span> &lt; 0.05, ** <span class="html-italic">p</span> &lt; 0.01, *** <span class="html-italic">p</span> &lt; 0.001, **** <span class="html-italic">p</span> &lt; 0.0001 vs. control. (ns: not significant).</p>
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<p>Evaluation of the antiproliferative potential of IMBZC on CRC cell migration using wound healing assay. (<b>A</b>) HT29 and (<b>B</b>) SW620 cells were seeded in 6-well plates and incubated with complete medium until confluence, and then the cell monolayer was scratched with a sterile 200 µL tip and washed with PBS. The medium was replaced with or without IMBZC then incubated for 24 h. Microscopy was used to examine the cells, and digital images were taken.</p>
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<p>The compound IMBZC inhibits HT29 and SW620 cell-based colony formation. Both HT29 (<b>A</b>) and SW620 (<b>B</b>) cells were incubated for 10–12 days at 37 °C for colony formation, along with untreated HT29 (<b>A</b>.<b>A</b>) and SW620 (<b>B</b>.<b>A</b>) cells (i.e., control). The number of colonies is represented by a bar graph and the data are presented as mean ± SD (N = 3). ** <span class="html-italic">p</span> &lt; 0.01, *** <span class="html-italic">p</span> &lt; 0.001, and **** <span class="html-italic">p</span> &lt; 0.0001 vs. control.</p>
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<p>Expression of mRNA levels of anti-apoptotic <span class="html-italic">BCL-2</span> and <span class="html-italic">BCL-xL</span> (<b>A</b>,<b>B</b>) and pro-apoptotic <span class="html-italic">BAX</span> and <span class="html-italic">TP53</span> (<b>C</b>,<b>D</b>) genes monitored in colorectal adenocarcinoma HT29 (<b>A</b>,<b>C</b>) and mCRC SW620 (<b>B</b>,<b>D</b>) (cell lines using RT-qPCR. Bar graphs show the relative gene expression levels calculated as a ratio to <span class="html-italic">GAPDH</span>, the internal control, and data are presented as mean ± SD (N = 3) * <span class="html-italic">p</span> &lt; 0.05, ** <span class="html-italic">p</span> &lt; 0.01, *** <span class="html-italic">p</span> &lt; 0.001, **** <span class="html-italic">p</span> &lt; 0.0001 vs. control.</p>
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<p>The effect of IMBZC on the anti-apoptotic Bcl-2 and Bcl-xl and pro-apoptotic Bax and p53 protein expression levels. (<b>A</b>) HT29 and (<b>B</b>) SW620 cells were treated for 24 h at different concentrations (7.94, 15.88 and 31.76 µM) of IMBZC. Anti-Bcl-2, Bcl-xl, p53, and Bax antibodies were used to target these proteins in whole cell lysates. The strength of protein bands was semi-quantified relative to β-actin, used as a loading control, and was presented as relative to protein expression, compared to the untreated control. The bar graphs show the mean ± SD of three independent experiments. * <span class="html-italic">p</span> &lt; 0.05, ** <span class="html-italic">p</span> &lt; 0.01, *** <span class="html-italic">p</span> &lt; 0.001, and **** <span class="html-italic">p</span> &lt; 0.0001 vs. control.</p>
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<p>IMBZC potentiates the cytotoxicity of CRC conventional drugs (i.e., 5-FU, IRI and OXA) in (<b>A</b>) HT29 and (<b>B</b>) SW620 cells. 5-FU, IRI, and OXA drugs were tested at different concentrations (2.5, 5 and 10 µM) for 24 h of incubation. Combinations of conventional drugs with the IMBZC compound on HT29 (<b>C</b>) and SW620 (<b>D</b>) cell lines. The cell viability percentage was determined using MTT assay. The bar graphs show the mean ± SD of three independent experiments. * <span class="html-italic">p</span> &lt; 0.05, ** <span class="html-italic">p</span> &lt; 0.01, *** <span class="html-italic">p</span> &lt; 0.001, and **** <span class="html-italic">p</span> &lt; 0.0001 vs. control.</p>
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