A GREEN CHEMISTRY APPROACH TO A DEVELOPMENT OF NOVEL

ANTIBACTERIAL AGENT
Contents
Abstract:.....................................................................................................................................................3
Keywords: Antimicrobial, Antibacterial agents, Phage therapy, Multi drug struggle.....................3
Introduction:..............................................................................................................................................3
Preventing pathogenesis:..........................................................................................................................4
1. Anti-toxins......................................................................................................................................5
2. Neutralization of toxins.................................................................................................................5
3. Immunoconjugates........................................................................................................................5
4. Immune-modulating antibodies....................................................................................................6
Biofilm prevention agent...........................................................................................................................6
Inhibitor of quorum sensor production...................................................................................................7
Inhibitor of QS signal receptor.................................................................................................................7
New antimicrobials against novel targets................................................................................................8
1. Cell wall target...............................................................................................................................8
Inhibitor of chorismate biosynthesis........................................................................................................9
Inhibitor of isoprenod biosynthesis........................................................................................................10
Alternative methods for combating microbes.......................................................................................11
1. Treatment with bacteriophages..................................................................................................11
Conclusion:..............................................................................................................................................11
REFERENCES:.......................................................................................................................................12
A GREEN CHEMISTRY APPROACH TO A DEVELOPMENT OF NOVEL
ANTIBACTERIAL AGENT

Abstract:
Over the past 50 years, antibiotics have helped advance modern medicine and save a great deal
more lives. the growth of medication resistance, which puts these treatments' ability to save lives
in danger. This clearly demonstrates the urgent necessity for brand-new, superior antibacterial
medications with a distinctively focused and innovative chemical structure agent to stop cross-
resistance. This study looked into prospective new approaches to the search for brand-new
antibacterial substances. Quorum sensor biosynthesis, numerous virulence factors, bacterial
division construction equipment, cellular membrane fabrication, PDF siderophore, monomeric
oxidases, bioconversion pathway synthesis, biofilm fabrication, and lipid biosynthesis are some
of the most thoroughly researched novel bacterial targets for drug development. There are now
drugs in preclinical trials thanks to these novel discovery pathways. The alternative methods that
operate on bacteria or other methods that target the person are also covered in this study. Phages
and antimicrobial peptides are two of the most cutting-edge techniques now in preclinical and
clinical research, respectively. These alternate methods may be used as complementary therapy,
indicating that traditional antibacterial drugs are still necessary.

Keywords: Antimicrobial, Uncontaminated agents, Phage therapy, Multi drug struggle

Introduction:
Human society has consistently utilized antibacterial medications for more than 70 years to treat
infections brought on by dangerous germs [1]. Despite the fact that these antibacterial drugs have
saved many lives and are a vital component of contemporary medicine, they have also caused
evolutionary stress on microorganisms and the need for drug-resistant mutations, which has
diminished their efficacy and caused them to be pulled from use [2]. Drug resistance causes a
tremendous deal of pain to people and is currently one of the biggest problems of the twentieth
century. The inappropriate or excessive use of antimicrobial drugs has led to the emergence of
species such the vancomycin-resistant Escherichia coli and methicillin-resistant S. aureus [3].
This amplifies the urgent need to develop and better antibacterial agents, which has prompted
extensive research into new molecular structures with novel modes of deed for application in
experimental practice [4]. Unfortunatelys, the pharmaceutical industry has identified too few
antibacterial medicines to replace those that are ineffective for this many kinds of diseases after
more than 50 years [5]. The pharmaceutical industry has been addressing this issue up to this
point by altering the current antibacterial medicines and creating new ones. But in the past forty
years, only a small number of antibacterial agent classes namely, triazoles, pleuromutilins,
tiacumicins, diarylquinolines lipopeptides, and streptogramins have been commercially
available, and the majority of them are used to treat gram-positive pathogenic bacteria [6], [7].
The issue of this illness has to be addressed from a wider perspective. One of the key strategies is
to find and advance new antiseptic medicines that will be effective against resistant species by
identifying, validating, and using prospective targets. Although there are many different
medicines utilized in clinical practice, there are only a few different targets that they can block
[8]. Through the screening of gene products produced by the expression of genes collected
directly from the ecosystem, microbiological genome analysis has revealed a significant number
of potentially relevant targets and helped to access uncultivable bacteria [8], [9].

Preventing pathogenesis:
Bacteria use virulence factors to influence the tissues of the host. The species and demography at
the time of the initial exposure determine its pathogenicity. These microorganisms quickly
activated the target genes once the infection has started in the host and create virulence
influences that help the microbe infiltrate the host, start the infection, and fight against the host
invulnerable classification [10],. These virulence factors include lipopolysaccharide toxins,
siderophores, polysaccharide capsules, invasion factors, and adhesion factors [11]. Without
actually killing the bacteria, preventing the production of these bacterial pathogens lowers the
evolutionary pressure on resistant genes, which reduces the likelihood of host invasion by the
bacteria. Inhibition of quorum-sensing compounds, toxin, obedience to the host cell, and life
form gene products expression are some of the primary pro strategies [12].
 1. Anti-toxins
Toxins are antigens that are released by in order to affect the healthy cells and trigger certain
antibodies known as antitoxins. Soluble exotoxins and bacterial surface targets are the targets of
bactericidal mAbs. Anti-exotoxin mAbs reduce bacterial pathogenicity in a variety of ways,
including exotoxin neutralization, monoclonal phagocytosis, counterbalance bactericidal action,
and death that is independent of the immune system [13], [14].

2. Neutralization of toxins
Through generating antibody-toxin complexes, antibacterial mAbs neutralize soluble exotoxins.
These complexes are predominantly eliminated by the reticuloendothelial. All of the antibacterial
mAbs that are currently on the market work by neutralizing toxins. Their ability to attach to the
poison determines how effective they are [15]. The first biologic product containing an anti-
protective antigen (PA) that has been authorized for use in treating anthrax infection with
antimicrobials is raxibacumab. It prevents the entry of anthrax edoema and deadly factor, which
are responsible for the infectious things of anthrax poison, into the cell. Another anti-PA mAb,
obilotoximab, was authorized to provide protection against the anthrax toxin by preventing PA
from interacting with receptor molecules on host cells [16], [21]. Bezlotoxumab is a human IgG1
that has been licensed to lower the risk of Caused by clostridium infection (CDI) recurrence in
people who are receiving antibiotics for CDI. It binds and prevents the host cell-toxin B binding.
As a result, it stops cells' downstream signaling pathways and Rho GTPases from being
inactivated by toxin B. Bezlotoxumab is therefore not recommended for treating CDI; rather, it is
solely suggested for preventing its recurrence [17].

In contrast to the medications mentioned above, other mAbs are undergoing clinical trials right
now. These six monoclonal antibodies (mAbs) were created to target S. aureus P.

3. Immunoconjugates

In order to effectively destroy intracellular microorganisms, the antibody promotes absorption

into lysosomes, where a strong sterile chemical shipment is unconfined. Compared to other
approaches, this one was more effective in killing vancomycin-resistant S. aureus [19].
Conjugates of antibodies and antigens are thought to have good pharmacokinetics (extended
half-lives) and reduce toxicity. Antibacterial medicines that failed in medical studies due to
undesirable pharmacokinetics or toxicities may also be used with immunoconjugates [20]. It
facilitates the precise delivery of radiation that kills bacteria to microorganisms. The
pneumococcal internal polysaccharide was the target of an example Bismuth-213-linked mAb
that demonstrated dose-dependent death in vitro. The IgG coupled to a sulfonamide equivalent is
an antibody that attaches to surfaces proteins of Staphylococcus aureus and releases the
medication to kill intracellular Staphylococcus aureus in a clinical study that is now in phase 1.

3. Immune-modulating antibodies
It could speed up the removal of microorganisms from the body by boosting the immune system
of the host. Anti-Programmed Death (PD)-1 mAb was found to be beneficial for treating
tuberculosis (TB) infection, according to studies. After receiving standard-of-care medication,
CD4+ and CD8+ T cells from TB patients showed a reduction in PD-1 and its ligands. T cells
obtained from TB patients were treated with anti-PD-1 mAb to restore cytokine production and
antigen response .

Biofilm prevention agent

Two-thirds of illnesses are brought on by biofilms, which are sticky clumps formed by bacteria.
The bacteria are protected by biofilm, which also increases their resistance to drugs by a factor of
a thousand. Due to their sophisticated lowest bactericidal absorption values, antimicrobial
therapy typically fails to remove biofilm from the infection area. The production of biofilms and
pathogenicity are facilitated by an increase in c-di-GMP level, according to studies. It is critical
to screen new anti-biofilm drugs with new therapeutics and modes of action since biofilm
development influences pathogenicity and sensitivity to antimicrobial treatments. To minimize
biofilm infections, the first technique involves altering c-di-GMP, while the second involves
blocking the community sensing pathway. Biofilm dispersion is brought on by the signaling
molecule nitric oxide (NO). External NO treatment activates the enzyme phosphodiesterases,
which breaks down the crucial biofilm formation regulator c-di-GMP, causing a shift to a
diatoms phenotype. Biofilm production is inhibited by synthetic cationic peptides made from
natural peptides such human cathelicidin LL-37, the antimicrobial peptide indolicidin, and
cathuitamycins. Guanosine method of generating 3′-diphosphate rnas, a signal in biofilm
development and maintenance, are bound and made easier to degrade by antimicrobial peptide
1018, which possesses strong broad-spectrum anti-biofilm action.
Inhibitor of quorum sensor production
Bacteria produce signaling molecules known as auto inducers that aid in communication and
population estimation. Bacteria simply reproduce to grow in number when the auto inducer level
is too low. When a certain amount is achieved, the pathogenicity increases, biofilms develop, and
their production is automatically induced. Quorum sensing (QS) is a possible target for future
antimicrobial drugs since they can stop QS from activating in vivo and lessen pathogenicity. The
inhibiting actions of QS compounds do not put pressure on the development of resistance since
QS does not contribute significantly to bacterial growth. Quorum quenching, also known as QS
Inhibition, is accomplished by devices and networks with antagonistic substances, preventing the
formation of autoinducers, and destroying the autoinducers.

Inhibitor of QS signal receptor

The most popular approach is a QS Signal receptor blocker using an analogue of the AHL
antigen of interest. It is a really big shot to say that receptor blockers will reduce virulence in
vivo, despite the fact that they function effectively in vitro. Utilizing Caenorhabditis worms, a
straightforward model of P. aeruginosa virulence has been developed. When these nematode
worms graze on a P. aeruginosa lawn, they quickly perish despite feeding on innocuous bacteria.
The creation of HCN and large number, both of which are under QS control, is what caused the
worm to die. When the worms consume wild-type P. aeruginosa, they are completely eradicated.
The killing is decreased to 10% when the QS knockout worms fed on P. aeruginosa, showing
that QS systems are necessary for the expression of complete virulence. Garlic extract decreased
the lifespan of worms fed adventurous P. aeruginosa to 40% and 5%. (Fig. 1).

Figure 1 QS signal receptor binding lead genes activation (B) QS-regulated phenotype inhibition.
New antimicrobials against novel targets
1. Antimicrobial agents' aim for C55-PP and lipid II

Bactoprenol, also known as undecaprenyl phosphate (C55-P), is a crucial lipid needed for the
production of PG, teichoic compounds, lipopolysaccharides, enteroantigens, and capsule
polysaccharides. Dephosphorylation of bactoprenol (C55-PP) has been suggested as a possible
target to find novel antibacterial substances. By sequestering C55-PP, the antibacterial
medication amphotericin b and tripropeptin C prevents PG production, leading to cell lysis and
the loss of cell integrity. A cyclic lipopeptide called friulimicin B suppresses the development of
new cell walls by generating a Ca2+-dependent complex with the bactoprenol phosphorus carrier
C55-P. Since C55-P serves as a transporter during the production of teichoic acid. Although
Lipid II, a membrane-anchored PG precursor, is required for PG production and is unknown to
play any function in eukaryotes, it might be a low-toxicity target. Different antimicrobial agents,
including as glycopeptides (such as vancomycin), nisin, ramoplanin, and mannopeptimycins,
inhibit lipid II. Additionally, colicin M was shown to be an enzyme that speeds up the
breakdown of lipids I and II.

Figure 2 PG synthesis with antimicrobial agents sited at the position corresponding to the step in the synthesis that they can
inhibit.
Inhibitor of chorismate biosynthesis
For the production of the aromatic amino acids, p-aminobenzoic acid, ubiquinone, vitamin K,
and enterchelin, bacteria need the Chorismate biosynthetic pathway. Since mammals lack this
route, it makes for a fresh antibacterial target. Since bacteria cannot obtain the pathway's
byproducts from the host, it is essential for their growth and development. Highly virulence-
attenuated strains are produced in vivo when one of the synthesis pathway, such as 5-
enolpyruvylshikimic acid-3-phosphate (EPSP) synthase, is altered or deleted. The
commercialized herbicide methotrexate, an inhibitor of EPSP synthase, uses the shikimate
pathway. The likelihood of targeting this route in these species is highlighted by the fact that it is
present in several microorganisms, including bacteria, fungus, and apicomplexan parasites. In
vitro, glyphosate prevents the development of gram-negative and gram-positive bacteria. It has
also been demonstrated that a few chorismate mutases, reverse transcriptase reductase, and
chorismate synthases are crucial.

Inhibitor of isoprenod biosynthesis

Because isoprenoids are essential for the production of peptidoglycans, A novel target for the
development of novel antimicrobials is the inhibition of isoprenoid synthesis. The source of
isoprenoid is isopentyl diphosphate (IPP) or its isomer, dimethylallyl pyrophosphate (DMAPP),
which are both created by different mechanisms, the mevalonate pathway and the other cm) in
diameter 4-phosphate (MEP) pathway. With a few exceptions, most organisms have two
different, mutually exclusive pathways, with the exception of several species of Streptomyces
and Legionella monocytogenes. The main method of IPP production in the majority of bacteria is
the MEP route, which necessitates several enzymatic steps. The mevalonate route is used by
eukaryotes to synthesize IPP, hence the novel antimicrobial medicines would block an enzyme
implicated in the MEP process.
 Figure 3 Isopreniod biosynthesis.

Alternative methods for combating microbes

1. Treatment with bacteriophages
Phages, sometimes known as "bacterium eaters," are viruses that infect bacteria. Phage therapy
employs viruses as a kind of infection prevention or treatment. Lysogenic phages are different
from lytic phages in that they integrate into the host genome as prophages, where they simulate
along with the host's cell DNA without lysing the host, making them suitable for treatment
because they cause the bacterium to burst and release phages to infect other bacteria. With the
release of offspring, the prophage may transition to the lytic phase, however these progeny may
not have the same medical applications as lytic phages. Phages can also transmit genes that
encode antimicrobial agents, synthesize AMP, target antimicrobial drug carriers, and infect
susceptible bacteria while still alive. Virolysins, a muralytic enzyme that degrades PG, are
encoded by tail phages. Because of its high potency (g/l) and lower resistance due to a mutation
in the bacterial cell wall, virolysins have lower immunogenicity and allergic reactions. Phages
contain chemical peptides like lytic factors, which function similarly to the virolysin-holin
system. Holin is a peptide that forms disruptive membrane lesions when it oligomerizes with
membrane, enabling virolysins to pass through the cell wall.
Conclusion:
Even though various research have been conducted over the past ten years to find new
antibacterial medicines by blocking the new targets, the outcomes have fallen short of
expectations. Technology advancements in bioinformatics, microbial genomes, target validation,
and screening methodologies have greatly improved the early phase of antibacterial drug
development, which include isolating, validating, and using prospective targets. Infectious illness
has been addressed in a promising way thanks to microbial genomics, which has presented a
viable target for the development of medicines with a target-based approach. By making the
cloning and production of desired genes easier, target-based approaches can replace direct
antibacterial screening. As possible targets for the isolation of novel antibacterial drugs, several
metabolic pathways have been discovered. The majority of these are crucial for screening,
increasing both the quantity and variety of agents being examined. Fatty acid manufacturing
inhibitor CG400549 (phase 2) and protein deformylase inhibitor GSK1322322 (phase II) are two
examples of antibacterial pipelines with unique targets. Murepavadin and brilacidin, which are
antibiotic alternatives, are in the second phase of a clinical investigation.

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