Development and validation of bioanalytical method for quantification of cycloserine in human plasma by liquid chromatography-tandem mass spectrometry: Application to pharmacokinetic study.

A selective, sensitive and high-throughput liquid chromatography-tandem mass spectrometry bioanalytical method has been developed for the estimation of cycloserine in human plasma, employing cytosine as the internal standard. The extraction of the analyte was facilitated by solid-phase extraction using 100 µL of human plasma. The separation was carried out on a BDS Hypersil C18 (150 × 4.6 mm, 5 µm) column using a mixture of 0.2% formic acid in HPLC-grade water, methanol and acetonitrile (70:15:15, v/v/v) as mobile phase at a flow rate of 1.0 mL/min. The method was linear over the range of 0.20-20 µg/mL with r2 > 0.99. Complete validation of the method was performed as per US Food and Drug Administration guidelines and the results met acceptance criteria. Applying the present method, the clinical pharmacokinetics of cycloserine following oral administration of 250 mg cycloserine was studied under fasting conditions. Assay reproducibility was also verified by incurred sample reanalysis.

High sensitive LC-MS/MS method for estimation of eluxadoline in human plasma and its application to pharmacokinetic study.

A selective, sensitive and high throughput liquid chromatography - tandem mass spectrometry (LC-MS/MS) method was developed and validated for estimation of eluxadoline in human plasma. Plasma samples of analyte with internal standard (eluxadoline13CD3) were extracted using solid phase extraction on Orochem Panthera Deluxe cartridges. Chromatographic separation was performed on Ace Phenyl column (150 × 4.6 mm, 5 µm), using a mixture of buffer (2 mM ammonium acetate in 0.01% formic acid), acetonitrile and methanol (20:70:10, v/v/v) as mobile phase at a flow rate of 0.8 mL/min. The run time of analyte was 4.0 min. Tandem mass spectrometry, operating in positive ionization and multiple reaction monitoring modes was used for detection of analyte and internal standard. The method was established with a linear dynamic range of 25.0-5000 pg/mL for eluxadoline using 300 µL human plasma. The sample preparation procedure was consistent and reproducible (accuracy, 96.2-106.1%; precision (%CV), 0.8-6.6%), preventing the ex vivo hydrolysis of acyl glucuronide metabolite of eluxadoline to parent drug. The method was applied successfully to a clinical pharmacokinetic study in six healthy South Indian male subjects under fed conditions and the results were authenticated by incurred sample reanalysis.

Development and validation of bioanalytical liquid chromatography-tandem mass spectrometry method for the estimation of pentoxifylline in human plasma: Application for a comparative pharmacokinetic study.

A method for bioanalysis of pentoxifylline in human plasma was developed using liquid chromatography-tandem mass spectrometry, which is simple, specific, and sensitive. Pentoxifylline D5 was used as the internal standard. Employing only 100 µl of human plasma, processing was done with solid-phase extraction technique. The analyte and the internal standard were separated from endogenous components on Ace phenyl column using a mixture of 5 mM ammonium acetate buffer and high performance liquid chromatography grade acetonitrile (60:40, v/v) as mobile phase at a flow rate of 1 ml/min. The linearity of the method was in the range of 3-1200 ng/ml with r2 > 0.99. Positive ion MRM mode was used for the detection of the analyte and the internal standard. The method was validated as per the US Food and Drug Administration guidelines and the results were within the acceptance limits. The proposed method was applied for comparative pharmacokinetic study of pentoxifylline after oral administration of 400 and 600 mg tablets to South Indian male subjects under fed conditions.

Fe3 O4 nanoparticles mediated synthesis of novel spirooxindole-dihydropyrimidinone molecules as Hsp90 inhibitors.

Heat shock protein 90 (Hsp90) is a validated molecular chaperone considered as the new key recipient for cancer intervention. The current study illustrates the synthesis of novel spirooxindole-dihydropyrimidinones (4a-j) by Fe3 O4 nanoparticles intervened synthesis and their Hsp90 ATPase inhibitory activity was investigated by the malachite green assay. All the compounds in the study demonstrated a moderate to potent ATPase inhibitory profile, with IC50 values ranging from 0.18 to 6.80 µM. Compounds 4j, 4h, 4f, and 4i exhibited maximum inhibitory potential with IC50 values of 0.18, 0.20, 0.35, and 0.55 µM, respectively. They were found to be better than the standard drug, geldanamycin (Hsp9 ATPase inhibition IC50 = 0.90 µM). Compounds 4h and 4j with IC50 values of 22.82 ± 0.532, 20.78 ± 0.234 and 21.32 ± 0.765, 28.43 ± 0.653 µM showed significantly greater potencies against the MCF-7 and HepG2 cell lines, respectively. Compound 4j showed good antioxidant activities in the DPPH test and H2 O2 assay (IC50 = 20.13.23 ± 0.32 and 23.27 ± 0.32 µg/mL) when compared with the standard ascorbic acid (IC50 = 19.16 ± 0.20 and 20.66 ± 1.09 µg/mL). A molecular docking study was performed to observe the binding efficiency and steric interactions of the lead moiety.

Fe3O4 Nanoparticles Mediated Synthesis of Novel Isatin-dihydropyrimidinone Hybrid Molecules as Antioxidant and Cytotoxic Agents.

BACKGROUND: The present study emphasizes on designing a new series of isatin-dihydropyrimidinone derivatives by adopting a hybrid pharmacophore approach. Fe3O4 nanoparticles (Fe3O4 NP) are magnetically recoverable and are effective catalysts adequately used to synthesize Isatin-dihydropyrimidinones. Individual derivatives of Isatin and dihydropyrimidinone are equipotent to treat cytotoxicity. OBJECTIVE: The present work was planned to fuse two pharmacophores (Isatin, dihydropyrimidinone) and to examine any synergistic effect in the anticancer activity. METHOD: The individual compounds are synthesized by adopting appropriate synthetic routes like sandmayers and biginellis reaction and are fused together by using glacial acetic acid and Methanolic KOH to form novel Isatindihydropyrimidinone hybrids. All the new series of hybrids 7a-l were characterized by FT-IR, 1H NMR, 13C NMR, elemental analysis and Mass spectroscopy. The antioxidant activity of the synthesized compounds was assessed by using two models: 1, 1-diphenyl-2-picryl-hydrazyl (DPPH) and Hydrogen peroxide (H2O2) scavenging assay. RESULTS: From the results it can be inferred that nearly all the synthesized compounds have shown antioxidant activity at the tested dose as correlated with the standard ascorbic acid. The in vitro cytotoxic activity was assayed by using MTT assay. Compound 7l with IC50 values 22.13, 25.68 and 35.59 µM has significantly greater potency against MCF- 7, HeLa and IMR-32 cell lines. CONCLUSION: The compounds with halogen and electron withdrawing groups at the C-5 position of isatin ring exhibited significant antioxidant and cytotoxic activity.

Liquid chromatography-tandem mass spectrometric assay for eltrombopag in 50µL of human plasma: a pharmacokinetic study.

Eltrombopag is a thrombopoietin receptor agonist, used in the treatment of thrombocytopenia. This paper describes a liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay method for the determination of eltrombopag in human plasma samples using eltrombopag 13C4 as internal standard (IS). Analyte and the IS were extracted from 50µL of human plasma using protein precipitation technique with no drying, evaporation and reconstitution steps. The chromatographic separation was achieved on a C18 column by using a mixture of 10mM ammonium formate (pH3) and acetonitrile (10:90, v/v) as the mobile phase at a flow rate of 1.0mL/min. The linearity of the method was established in the concentration range 50.0-10007ng/mL with r(2)≥0.99. The intra-day and inter-day precision and accuracy results in four validation batches across five concentration levels were well within the acceptance limits. The proposed method was found to be applicable to pharmacokinetic studies.

Liquid chromatography-tandem mass spectrometric assay for the non-nucleoside reverse transcriptase inhibitor rilpivirine in human plasma.

An analytical method based on liquid chromatographic-tandem mass spectrometry (LC-MS/MS) was developed for the determination of the non-nucleoside reverse transcriptase inhibitor rilpivirine in human plasma using nevirapine as an internal standard. Analyte and the internal standard were extracted from human plasma by liquid-liquid extraction. The reconstituted samples were chromatographed on a C(18) column using a mixture of acetonitrile and 0.1% formic acid buffer (80:20, v/v) as the mobile phase at a flow rate of 0.5 mL/min. The linearity was confirmed in the concentration range 0.51-200 ng/mL in human plasma. Multiple reaction monitoring mode was used for quantification of ion transitions at m/z 367.2/195.1 and 267.1/226.1 for the drug and the internal standard, respectively. The results of the intra- and inter-day precision and accuracy studies were well within the acceptable limits. Extraction recoveries of drug from plasma were >69.5%. A run time of 2.50 min for each sample made it possible to analyze more than 300 plasma samples per day. The developed method is simple, rapid and sensitive for the determination of rilpivirine concentrations in real-time plasma samples obtained from pharmacokinetic studies.

Simultaneous determination of sitagliptin and simvastatin in human plasma by LC-MS/MS and its application to a human pharmacokinetic study.

A simple, rapid and sensitive liquid chromatography-tandem mass spectrometric (LC-MS/MS) assay method has been developed and validated for simultaneous quantification of sitagliptin and simvastatin in human plasma. Carbamazepine was used as an internal standard (IS). The analytes and IS were extracted from the human plasma by liquid-liquid extraction technique. The reconstituted samples were chromatographed on an Alltima HP C(18) column using an isocratic solvent mixture [acetonitrile-5 mm ammonium acetate (pH 4.5), 85:15 (v/v)] at a flow rate of 1.0 mL/min. Method validation was performed as per Food and Drug Administration guidelines and the results met the acceptance criteria. The calibration curves obtained were linear (r(2) ≥ 0.99) over the concentration range of 0.10-501 and 0.05-105 ng/mL for sitagliptin and simvastatin, respectively. The results of the intra- and inter-day precision and accuracy studies were well within the acceptable limits. Both the analytes were found to be stable in a battery of stability studies. The method is precise and sensitive enough for its intended purpose. A run time of 3.0 min for each sample made it possible to analyze more than 300 plasma samples per day. The developed assay was successfully applied to a pharmacokinetic study in human volunteers.