Nourah Z. Alzoman

Simultaneous determination of selected tyrosine kinase inhibitors with corticosteroids and antiemetics in rat plasma by solid phase extraction and ultra-performance liquid chromatography–tandem mass spectrometry: Application to pharmacokinetic interaction studies

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 0.2 mL/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 0.05-100 ng/mL plasma (PRED, DEX) with very low lower limit of quantification of 0.025 (GEF, ERL, OND) and 0.05 ng/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.

Analytical Study for the Charge-Transfer Complexes of Rosuvastatin Calcium with π-Acceptors

Studies were carried out to investigate the charge-transfer (CT) reaction of ROS-Ca, as a n-electron donor with various π-acceptors: tetracyanoethylene, p-chloranilic acid, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone, 2,3,5,6-tetrabromo-1,4-benzoquinone, 1,3,5-trinitrobenzene, 2,3,5,6-tetrachloro-1,4-benzoquinone, 7,7,8,8-tetracyano-quinodimethane, and 2,4,7-trinitro-9-fluorenone. Different colored CT complexes were obtained. The reaction mechanism and site of interaction were determined by ultraviolet-visible spectrophotometric techniques and computational molecular modeling. The formation of the colored complexes was utilized in the development of simple, rapid and accurate spectrophotometric methods for the determination of ROS-Ca. Under the optimum reaction conditions, linear relationships with good correlation coefficients (0.9984–0.9995) were found between the absorbances and the concentrations of ROS-Ca in the range of 2–200 μg mL−1. The limits of detection ranged from 0.41 to 12.24 μg mL−1. No interference could be observed from the additives commonly present in the tablets or from the drugs that are co-formulated with ROS-Ca in its combined formulations. The methods were successfully applied to the analysis of tablets with good accuracy and precision; the recovery percentages ranged from 99.54–100.46 ± 1.58–1.82%. The results were compared favorably with the reported method. The proposed methods are practical and valuable for routine application in quality control laboratories for determination of ROS-Ca in its bulk form and tablets.

Simultaneous determination of erlotinib and tamoxifen in rat plasma using UPLC–MS/MS: Application to pharmacokinetic interaction studies

Tamoxifen (TAM) is a non-steroidal estrogen receptor antagonist that enhances erlotinib (ERL)-induced cytotoxicity in the treatment of NSCLC. ERL and TAM are metabolized by CYP3A4 enzymes. In addition, both drugs have the potential of altering the enzymatic activity through either inhibition (ERL) or induction (TAM). Thus it was expected that pharmacokinetics (PK) drug-drug interactions (DDIs) could be encountered following their co-administration. In this respect, a bioanalytical UPLC-MS/MS method has been developed and validated for the simultaneous determination of ERL and TAM in rat plasma samples, using ondansetron (OND) as an internal standard (IS). Plasma samples were prepared using mixed mode cationic solid phase extraction (SPE) STRATA™ -X-C 33μm cartridges with good extraction recovery of both drugs from rat plasma (Er% from -13.92 to -3.32). The drugs were separated on a Waters BEH™ C18 column with an isocratic elution using a mobile phase composed of a mixture of acetonitrile and water, each with 0.15% formic acid, in the ratio of 80: 20, v/v. Quantitation was carried out using the positive ionization mode with multiple reaction monitoring (MRM) at m/z 394.20>278.04 (ERL), m/z 372.25>72.01 (TAM), and m/z 294.18>170.16 (OND). The method was fully validated as per the FDA guidelines over the concentration range of 0.2-50ng/mL with very low lower limit of quantification (LLOQ) of 0.2ng/mL for both ERL and TAM. The intra- and inter-day assay precision (in terms of relative standard deviation, RSD) and accuracy (in terms of percentage relative error, % Er) were evaluated for both drugs and the calculated values evaluated at four different concentration levels were within the acceptable limits (<15%) for concentrations other than LLOQ and 20% for LLOQ. The method was successfully applied to the study of possible PK-DDI following the oral administration of ERL and TAM in a combination, compared to their single administration.

Determination of Luteolin and Apigenin in Herbs by Capillary Electrophoresis with Diode Array Detection

Capillary electrophoresis with a diode array detector was employed for the determination of luteolin and apigenin in plant extracts. The experimental factors affecting the elution of the analytes were carefully optimized. The final analysis was achieved utilizing a fused silica capillary (58 cm effective length, 75 μm ID) and a background electrolyte solution consisting of borax buffer (20 mM, pH 10.0) and methanol (90: 10, v/v) with a 23 kV driving voltage and detection at 210 nm. The method was fully validated as per the guidelines of the International Conference on Harmonization for Analytical Procedures. The relationship between peak area and concentration was linear between 3 and 800 μg/mL for both compounds with detection limits of 1.05 for luteolin and 0.53 μg/mL for apigenin. The method was employed for the determination of the analytes in extracts of thyme and parsley. Both compounds were resolved from interfering peaks that were present in the extracts. Recovery studies were performed by fortifying the extracts with standards and demonstrated good accuracy with recovery values between 97.29 and 104.88% for luteolin and 96.89 and 105.18% for apigenin. Thyme and parsley were shown to contain high concentrations of luteolin and apigenin.

UPLC–ESI–MS/MS study of the effect of green tea extract on the oral bioavailability of erlotinib and lapatinib in rats: Potential risk of pharmacokinetic interaction

Green tea (GT) is one of the most consumed beverages worldwide. Tyrosine kinase inhibitors (TKIs) belong to the oral targeted therapy that gained much interest in oncology practice, among which are erlotinib (ERL) and lapatinib (LAP). Since green tea polyphenols (GTP) are known to be inhibitors of receptor tyrosine kinases, GTE could likely potentiate the anticancer effect of TKIs, but with a possibility of pharmacokinetic (PK) interaction with co-administered TKIs. In this study, the effect of GTE on the PK of ERL/LAP in rats was studied. UPLC-ESI-MS/MS method has been developed and validated for the quantification of ERL and LAP in rat plasma, using gefitinib (GEF) as the internal standard. Plasma samples were treated extensively by protein precipitation (PPT) followed by solid phase extraction (SPE) using octadecyl C 18/14% cartridges. Chromatographic analysis was carried out on Acquity UPLC BEH™ C18 column with a mobile phase consisting of water: acetonitrile (20: 80, v/v), each with 0.15% formic acid. Quantification was performed in the positive electrospray ionization (ESI+) mode with multiple reaction monitoring (MRM) of the transitions m/z 394.29→278.19 (ERL), m/z 581.07→365.13 (LAP), and m/z 447.08→128.21 (GEF). The method was fully validated as per the FDA guidelines showing linearity over the range of 0.4-1000 (ERL) and 0.6-1000 (LAP) ng/mL with very low lower limit of quantification (LLOQ) of 0.4 and 0.6ng/mL for ERL and LAP, respectively. The applicability of the method was extended to perform a comparative study of the PK of ERL/LAP following short-term and long-term administration of GTE, compared with their single oral administration. The results revealed that a significant reduction in the oral bioavailability was recorded with both ERL and LAP following the ingestion of GTE particularly for short-term administration. A reduction in Cmax (AUC) by 67.60% (69.50%) and 70.20% (73.96%), was recorded with short-term administration of GTE, compared with only 16.03% (21.09%) and 13.53% (22.12%) reduction for ERL and LAP, respectively, with long-term administration. Thus patients taking TKIs should preferably avoid drinking GT or ingesting GTE capsules during the period of treatment with TKIs.

Spectroscopic investigation (FT-IR and FT-Raman), vibrational assignments, HOMO-LUMO, NBO, MEP analysis and molecular docking study of 2-((4-chlorobenzyl)sulfanyl)-4-(2-methylpropyl)-6- (phenylsulfanyl)-pyrimidine-5-carbonitrile, a potential chemotherapeutic agent

Vibrational spectral analysis of 2-[(4-chlorobenzyl)sulfanyl]-4-(2-methylpropyl)-6-(phenylsulfanyl)-pyrimidine-5-carbonitrile was carried out using FT-IR and FT-Raman spectroscopic techniques. The equilibrium geometry and vibrational wave numbers have been computed using density functional B3LYP method with 6-311++G(d,p)(5D,7F) as basis set. Stability of the molecule arising from hyper conjugative interactions, charge delocalization has been analyzed using NBO analysis. The nonlinear optical behavior of the title compound is also theoretically predicted. From the MEP, it is evident that the negative charge covers the C≡N group and the positive region is over the phenyl and the pyrimidine rings. From the potential energy scan it is clear that the lone pairs of the sulfur atom prefer to point away from the pyrimidine ring and the C≡N group resulting with two possible minimum conformations at the N4C8S1C25 angle equal nearly 0° or 150°. Molecular docking results suggest that the compound might exhibit inhibitory activity against GPb and may act as potential anti-diabetic compound.

Charge-transfer reaction of 1,4-benzoquinone with crizotinib: spectrophotometric study, computational molecular modeling and use in development of microwell assay for crizotinib.

The reaction of 1,4-benzoquinone (BQ) with crizotinib (CZT); a novel drug used for treatment of non-small cell lung cancer) was investigated in different solvents of varying dielectric constants and polarity indexes. The reaction resulted in the formation of a red-colored product. Spectrophotometric investigations confirmed that the reaction proceeded through charge-transfer (CT) complex formation. The molar absorptivity of the complex was found to be linearly correlated with the dielectric constant and polarity index of the solvent; the correlation coefficients were 0.9425 and 0.8340, respectively. The stoichiometric ratio of BQ:CZT was found to be 2:1 and the association constant of the complex was found to be 0.26×10(3)lmol(-1). The kinetics of the reaction was studied; the order of the reaction, rate and rate constant were determined. Computational molecular modeling for the complex between BQ and CZT was conducted, the sites of interaction on CZT molecule were determined, and the mechanism of the reaction was postulated. The reaction was employed as a basis in the development of a novel 96-microwell assay for CZT. The assay limits of detection and quantitation were 5.2 and 15.6μgml(-1), respectively. The assay was validated as per the guidelines of the International Conference on Harmonization (ICH) and successfully applied to the analysis of CZT in its bulk and capsules with good accuracy and precision. The assay has high throughput and consumes minimum volume of organic solvent thus it reduces the exposures of the analysts to the toxic effects of organic solvents, and significantly reduces the analysis cost.

Novel Stereoselective High-Performance Liquid Chromatographic Method for Simultaneous Determination of Guaifenesin and Ketorolac Enantiomers in Human Plasma

A novel method was developed for the simultaneous determination of guaifenesin (GUA) and ketorolac tromethamine (KET) enantiomers in plasma samples. Since GUA probably increases the absorption of coadministered drugs (e.g., KET), it would be extremely important to monitor KET plasma levels for the purpose of dose adjustment with a subsequent decrease in the side effects. Enantiomeric resolution was achieved on a polysaccharide-based chiral stationary phase, amylose-2, as a chiral selector under the normal phase (NP) mode and using ornidazole (ORN) as internal standard. This innovative method has the advantage of the ease and reliability of sample preparation for plasma samples. Sample clean-up was based on simply using methanol for protein precipitation followed by direct extraction of drug residues using ethanol. Both GUA and KET enantiomers were separated using an isocratic mobile phase composed of hexane/isopropanol/trifluoroacetic acid, 85:15:0.05 v/v/v. Peak area ratios were linear over the range 0.05-20 µg/mL for the four enantiomers S (+) GUA, R (-) GUA, R (+) KET, and S (-) KET. The method was fully validated according to the International Conference on Harmonization (ICH) guidelines in terms of system suitability, specificity, accuracy, precision, robustness, and solution stability. Finally, this procedure was innovative to apply the rationale of developing a chiral high-performance liquid chromatography (HPLC) procedure for the simultaneous quantitative analysis of drug isomers in clinical samples.

Stereoselective HPLC analysis of tertatolol in rat plasma using macrocyclic antibiotic chiral stationary phase

Enantiomeric resolution of teratolol was achieved on a vancomycin macrocyclic antibiotic chiral stationary phase known as Chirobiotic V with UV detection set at 220 nm. The polar ionic mobile phase (PIM) consisted of methanol-glacial acetic acid-triethylamine (100:0.01:0.015, v/v/v) has been used at a flow rate of 0.8 ml min(-1) . The calibration curves in plasma were linear over the range of 5-500 ng ml(-1) for each enantiomer with detection limit of 2 ng ml(-1) . The proposed method was validated in compliance with the international conference on harmonization (ICH) guidelines. The developed method applied for the trace analyses of tertatolol enantiomers in plasma and for the pharmacokinetic study of tertatolol enantiomers in rat plasma. The assay proved to be suitable for therapeutic drug monitoring and chiral quality control for tertatolol formulations by HPLC.

Comparative pharmacokinetic profiles of selected irreversible tyrosine kinase inhibitors, neratinib and pelitinib, with apigenin in rat plasma by UPLC–MS/MS

&NA; Neratinib (NER) and pelitinib (PEL) are irreversible tyrosine kinase inhibitors (TKIs) that have been recently employed in cancer treatment. Apigenin (API), among other flavonoids, is known to have antioxidant, anti‐proliferative, and carcinogenic effect. API can potentiate the antitumor effect of chemotherapeutic agents and/or alleviate the side effects of many anticancer agents. Since TKIs are mostly metabolized by CYP3A4 enzymes and that API could alter the enzymatic activity, potential drug interactions could be expected following their co‐aministration. In the present study, a bioanalytical UPLC–MS/MS method has been developed and validated for the quantification of NER and PEL in rat plasma, using domperidone (DOM) as an internal standard. Sample preparation was carried out using solid phase extraction (SPE) with C18 cartridges with good extraction recovery of not less than 92.42% (NER) and 89.73% (PEL). Chromatographic analysis was performed on a Waters BEH C18 column with a mobile phase composed of acetonitrile and water, (70:30, v/v), each with 0.1% formic acid. Quantitation was performed using multiple reaction monitoring (MRM) of the transitions from protonated precursor ions [M+H]+, at m/z 557.30 (NER), m/z 468.21 (PEL), and at m/z 426.27 (DOM), to selected product ions at m/z 112.05 (NER), m/z 395.22 (PEL), and at m/z 175.18 (DOM). The method was fully validated as per the FDA guidelines over the concentration range of 0.5–200 ng/mL with very low lower limit of quantification (LLOQ) of 0.5 ng/mL for both NER and PEL. The intra‐ and inter‐day assay precision and accuracy were evaluated for both drugs and the calculated values of percentage relative standards deviations (%RSD) and relative errors (%Er) were within the acceptable limits (<15%) for concentrations other than LLOQ and 20% for LLOQ. The applicability of the method was extended to study the possibility of drug interactions following the oral co‐administration of NER/PEL with API. Thus, this study could be readily applied in therapeutic drug monitoring (TDM) of cancerous patients receiving such drug combinations. Graphical abstract Figure. No caption available. HighlightsIt is the first time to report the simultaneous determination of neratinib and pelitinib in rat plasma.The proposed SPE‐ UPLC–MS/MS method was fully validated.The method offers great selectivity with low limits of quantification.The method has been successfully applied to pharmacokinetic interaction studies with apigenin.