SARS-CoV-2 virus triggered a worldwide crisis, with world nations putting up massive efforts to h... more SARS-CoV-2 virus triggered a worldwide crisis, with world nations putting up massive efforts to halt its spread. Molnupiravir (MLN) was the first oral, direct-acting antiviral drug approved for nasopharyngeal SARS-CoV-2 infection with favorable safety and tolerability profile. This study aims at determination of MLN and N4-hydroxycytidine (NHC), its main degradation product and its main metabolite, using sensitive, simple, and green HPLC–DAD method. Moreover, under different stress conditions using NaOH, HCl, neutral, H2O2, dry heat and sun light, the method was applied for MLN assay along with kinetics degradation investigation. The linearity range for MLN and NHC were both 0.1–100 µg/mL with LOD and LOQ of 0.013 & 0.043 and 0.003 & 0.011 µg/mL, for MLN and NHC, respectively. MLN was found to be extremely vulnerable to alkali hydrolysis compared with acid and dry heat degradation. In contrast, MLN was stable under conditions of oxidative, neutral, and sunlight-induced deterioration...
The SARS-CoV-2 virus sets up a global catastrophe, and countries all around the world made signif... more The SARS-CoV-2 virus sets up a global catastrophe, and countries all around the world made significant efforts to halt the spread. Nirmatrelvir (NMV) was lately approved by the FDA as a safe and well-tolerated oral direct-acting antiviral medication for SARS-CoV-2 virus infection. Therefore, a fast completely validated stability indicating method was established-for the first time- for NMV determination. The study used NaOH, HCl, neutral, H2O2, and sunlight to test NMV stability under various stress conditions followed by kinetics degradation investigation and derivation of Arrhenius plot. The analysis was performed using Agilent Zorbax Eclipse-C18 column (5 µm, 4.6 × 250 mm) with a mobile phase consisting of acetonitrile: 50 mM ammonium acetate, pH = 5 (50:50, v/v, respectively) at a flow rate of 1.0 mL/min with 5 min run time. Diode array detector (DAD) was set at 225 nm to quantify NMV at the concentration range of 5–500 µg/mL with LOD and LOQ of 0.6 and 2 µg/mL, respectively. Me...
Journal of Pharmaceutical and Biomedical Analysis, 2016
A sensitive and selective ultra-performance liquid chromatography-tandem mass spectrometry method... more A sensitive and selective ultra-performance liquid chromatography-tandem mass spectrometry method has been developed and validated for the simultaneous analysis of selected tyrosine kinase inhibitors (TKIs)(gefitinib GEF, erlotinib ERL), corticosteroids (dexamethasone DEX, prednisolone PRED), and the antiemetic ondansetron (OND) in rat plasma samples. After the addition of domperidone (DOM) as internal standard (IS), spiked plasma samples were prepared using the solid phase extraction (SPE) C 18 cartridges. Chromatographic separation was performed on a Waters BEH C18 column with an isocratic elution using a mobile phase composed of acetonitrile and water, each with 0.1% formic acid, (80: 20, v/v), at a flow rate of 0.2mL/min. Quantitation of the analytes was performed using the multiple reaction monitoring (MRM) mode with the positive ionization mode at m/z 447.25>128.08 (GEF), m/z 394.20>278.04 (ERL), m/z 393.30>147.04 (DEX), m/z 361.29>147.02 (PRED), m/z 294.18>170.16 (OND), and m/z 426.26>175.07 (DOM). The method was validated over the concentration range of 0.025-100 (GEF, ERL, OND) and 0.05-100ng/mL plasma (PRED, DEX) with very low lower limit of quantification of 0.025 (GEF, ERL, OND) and 0.05ng/mL (DEX, PRED). The intra- and inter-day precision (RSD%) evaluated at four different concentration levels were within the acceptable limits (<15%). The method provided good extraction recovery of all analytes from rat plasma (Er% from -14.05 to -1.08). The validated method was successfully applied to the pharmacokinetic studies following the oral administration of selected combinations of the studied drugs. This study can be readily applied in therapeutic drug monitoring (TDM) in patients receiving these drug combinations as well as investigation of possible drug interactions between TKIs and DEX/PRED/OND.
ABSTRACT Two stability-indicating chromatographic methods are reported for the determination of m... more ABSTRACT Two stability-indicating chromatographic methods are reported for the determination of methyl gallate in crude extracts of Bauhinia retusa. Separation by high performance thin layer chromatography was conducted on silica gel aluminum sheets using 9.5:0.5:0.2 (v/v/v) chloroform:methanol:acetic acid at 280 nm. The results from the 2–40 µg/band were used to prepare a linear calibration graph. The limits of detection and quantitation were 0.5 and 1.5 µg/band, respectively. The reverse phase high performance liquid chromatographic isolation of methyl gallate was performed at ambient temperature with an injection volume of 10 μL. The mobile phase consisted of 40:60 (v/v) methanol:0.1% ortho-phosphoric acid. The separation was performed at 1 mL/min using a detection wavelength of 280 nm. The calibration graph for methyl gallate was rectilinear from 0.02–40 µg/mL with limits of detection and quantitation of 0.004 and 0.010 µg/mL, respectively. For both methods, intra-day and inter-day precision were evaluated and the relative standard deviation was less than 2%, indicating good precision. The robustness was evaluated by making small and deliberate changes to appropriate parameters and the calculated relative standard deviation was less than 2%.The chromatographic methods were employed to determine methyl gallate in crude Bauhinia retusa extracts.
Gas chromatography with infrared detection (GC-IRD) provides direct confirmatory data for the ide... more Gas chromatography with infrared detection (GC-IRD) provides direct confirmatory data for the identification of the drug of abuse; 3,4-MDMA and its regioisomer; 2,3-MDMA, from a set of seven tertiary amines which have an isobaric or regioisomeric relationship with the MDMAs. These compounds include three ring substituted regioisomers of 2-dimethylamino-1-(methoxyphenyl)ethanone, two ring regioisomers of N,N-dimethyl-2-(methoxymethylphenyl)ethanamine in addition to N,N-dimethyl-2-(2,3- and 3,4-methylenedioxyphenyl)ethanamine. The major mass spectral fragments for each of these unique isomers occur at equivalent mass and all have equal molecular weight. Thus, gas chromatography with mass spectrometry detection (GC-MS) does not provide sufficient information for the confirmation of identity of any one of these isomers to the exclusion of the other compounds. The infrared spectra for these compounds allow for identification of any one of these amines. This differentiation is accomplished without the aid of chemical derivatization. The IR spectra served to divide the studied compounds into four groups depending on their absorption bands in the region 2700-3100 cm(-1). Moreover, compounds with different ring substitution pattern within each group can be differentiated by several bands in the 700-1700 cm(-1) region. These regioisomeric substances are well resolved by GC on Rtx-1 stationary phase and the vapor-phase infrared spectra clearly differentiate among this set of compounds.
SARS-CoV-2 virus triggered a worldwide crisis, with world nations putting up massive efforts to h... more SARS-CoV-2 virus triggered a worldwide crisis, with world nations putting up massive efforts to halt its spread. Molnupiravir (MLN) was the first oral, direct-acting antiviral drug approved for nasopharyngeal SARS-CoV-2 infection with favorable safety and tolerability profile. This study aims at determination of MLN and N4-hydroxycytidine (NHC), its main degradation product and its main metabolite, using sensitive, simple, and green HPLC–DAD method. Moreover, under different stress conditions using NaOH, HCl, neutral, H2O2, dry heat and sun light, the method was applied for MLN assay along with kinetics degradation investigation. The linearity range for MLN and NHC were both 0.1–100 µg/mL with LOD and LOQ of 0.013 & 0.043 and 0.003 & 0.011 µg/mL, for MLN and NHC, respectively. MLN was found to be extremely vulnerable to alkali hydrolysis compared with acid and dry heat degradation. In contrast, MLN was stable under conditions of oxidative, neutral, and sunlight-induced deterioration...
The SARS-CoV-2 virus sets up a global catastrophe, and countries all around the world made signif... more The SARS-CoV-2 virus sets up a global catastrophe, and countries all around the world made significant efforts to halt the spread. Nirmatrelvir (NMV) was lately approved by the FDA as a safe and well-tolerated oral direct-acting antiviral medication for SARS-CoV-2 virus infection. Therefore, a fast completely validated stability indicating method was established-for the first time- for NMV determination. The study used NaOH, HCl, neutral, H2O2, and sunlight to test NMV stability under various stress conditions followed by kinetics degradation investigation and derivation of Arrhenius plot. The analysis was performed using Agilent Zorbax Eclipse-C18 column (5 µm, 4.6 × 250 mm) with a mobile phase consisting of acetonitrile: 50 mM ammonium acetate, pH = 5 (50:50, v/v, respectively) at a flow rate of 1.0 mL/min with 5 min run time. Diode array detector (DAD) was set at 225 nm to quantify NMV at the concentration range of 5–500 µg/mL with LOD and LOQ of 0.6 and 2 µg/mL, respectively. Me...
Journal of Pharmaceutical and Biomedical Analysis, 2016
A sensitive and selective ultra-performance liquid chromatography-tandem mass spectrometry method... more A sensitive and selective ultra-performance liquid chromatography-tandem mass spectrometry method has been developed and validated for the simultaneous analysis of selected tyrosine kinase inhibitors (TKIs)(gefitinib GEF, erlotinib ERL), corticosteroids (dexamethasone DEX, prednisolone PRED), and the antiemetic ondansetron (OND) in rat plasma samples. After the addition of domperidone (DOM) as internal standard (IS), spiked plasma samples were prepared using the solid phase extraction (SPE) C 18 cartridges. Chromatographic separation was performed on a Waters BEH C18 column with an isocratic elution using a mobile phase composed of acetonitrile and water, each with 0.1% formic acid, (80: 20, v/v), at a flow rate of 0.2mL/min. Quantitation of the analytes was performed using the multiple reaction monitoring (MRM) mode with the positive ionization mode at m/z 447.25>128.08 (GEF), m/z 394.20>278.04 (ERL), m/z 393.30>147.04 (DEX), m/z 361.29>147.02 (PRED), m/z 294.18>170.16 (OND), and m/z 426.26>175.07 (DOM). The method was validated over the concentration range of 0.025-100 (GEF, ERL, OND) and 0.05-100ng/mL plasma (PRED, DEX) with very low lower limit of quantification of 0.025 (GEF, ERL, OND) and 0.05ng/mL (DEX, PRED). The intra- and inter-day precision (RSD%) evaluated at four different concentration levels were within the acceptable limits (<15%). The method provided good extraction recovery of all analytes from rat plasma (Er% from -14.05 to -1.08). The validated method was successfully applied to the pharmacokinetic studies following the oral administration of selected combinations of the studied drugs. This study can be readily applied in therapeutic drug monitoring (TDM) in patients receiving these drug combinations as well as investigation of possible drug interactions between TKIs and DEX/PRED/OND.
ABSTRACT Two stability-indicating chromatographic methods are reported for the determination of m... more ABSTRACT Two stability-indicating chromatographic methods are reported for the determination of methyl gallate in crude extracts of Bauhinia retusa. Separation by high performance thin layer chromatography was conducted on silica gel aluminum sheets using 9.5:0.5:0.2 (v/v/v) chloroform:methanol:acetic acid at 280 nm. The results from the 2–40 µg/band were used to prepare a linear calibration graph. The limits of detection and quantitation were 0.5 and 1.5 µg/band, respectively. The reverse phase high performance liquid chromatographic isolation of methyl gallate was performed at ambient temperature with an injection volume of 10 μL. The mobile phase consisted of 40:60 (v/v) methanol:0.1% ortho-phosphoric acid. The separation was performed at 1 mL/min using a detection wavelength of 280 nm. The calibration graph for methyl gallate was rectilinear from 0.02–40 µg/mL with limits of detection and quantitation of 0.004 and 0.010 µg/mL, respectively. For both methods, intra-day and inter-day precision were evaluated and the relative standard deviation was less than 2%, indicating good precision. The robustness was evaluated by making small and deliberate changes to appropriate parameters and the calculated relative standard deviation was less than 2%.The chromatographic methods were employed to determine methyl gallate in crude Bauhinia retusa extracts.
Gas chromatography with infrared detection (GC-IRD) provides direct confirmatory data for the ide... more Gas chromatography with infrared detection (GC-IRD) provides direct confirmatory data for the identification of the drug of abuse; 3,4-MDMA and its regioisomer; 2,3-MDMA, from a set of seven tertiary amines which have an isobaric or regioisomeric relationship with the MDMAs. These compounds include three ring substituted regioisomers of 2-dimethylamino-1-(methoxyphenyl)ethanone, two ring regioisomers of N,N-dimethyl-2-(methoxymethylphenyl)ethanamine in addition to N,N-dimethyl-2-(2,3- and 3,4-methylenedioxyphenyl)ethanamine. The major mass spectral fragments for each of these unique isomers occur at equivalent mass and all have equal molecular weight. Thus, gas chromatography with mass spectrometry detection (GC-MS) does not provide sufficient information for the confirmation of identity of any one of these isomers to the exclusion of the other compounds. The infrared spectra for these compounds allow for identification of any one of these amines. This differentiation is accomplished without the aid of chemical derivatization. The IR spectra served to divide the studied compounds into four groups depending on their absorption bands in the region 2700-3100 cm(-1). Moreover, compounds with different ring substitution pattern within each group can be differentiated by several bands in the 700-1700 cm(-1) region. These regioisomeric substances are well resolved by GC on Rtx-1 stationary phase and the vapor-phase infrared spectra clearly differentiate among this set of compounds.
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Papers by Hadir Maher