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For the first time, a rapid and sensitive high-performance liquid chromatography-tandem mass spectrometry (LC–MS/MS) method was developed for the simultaneous determination of fraxin and its metabolite, fraxetin, in rat plasma, using esculin as the internal standard (IS). The plasma samples were precipitated with methanol before separation on an Nova-Pak C 18 column (150 mm × 3.9 mm, 3 μm) using a mobile phase consisting of 0.1% formic acid and methanol (55:45) at a flow rate of 0.8 mL/min. The analytes were detected by multiple reaction monitoring in the negative ion mode with the mass transitions at m / z 368.9→ m / z 191.9 (fraxin), m / z 206.9→ m / z 191.8 (fraxetin) and m / z 339.0→ m / z 176.9 (esculin, IS). The results demonstrated that the calibration curves for both analytes have good linearity (r ≥ 0.995) over a concentration range of 5.00–3000 ng/mL. The assay was validated according to the regulatory bioanalytical guidelines and proved acceptable. The intra- and inter-day precisions (R.S.D.%) were within 10.9% for both analytes, whereas the deviation of assay accuracies (R.E.%) ranged from −5.3 to 1.0%. The method was successfully applied to a pharmacokinetic study after a single oral dose of fraxin at 50 mg/kg to rats. [ABSTRACT FROM AUTHOR]

Efficacy assessments using a combination of ibrutinib and lenalidomide necessitate the development of an analytical method for determination of both drugs in plasma with precision. A high performance liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed for the simultaneous determination of lenalidomide, ibrutinib, and its active metabolite PCI45227 in rat plasma. Extraction of lenalidomide, ibrutinib, PCI45227 and tolbutamide (internal standard; IS) from 50 μl rat plasma was carried out by liquid–liquid extraction with ethyl acetate:dichloromethane (90:10) ratio. Chromatographic separation of analytes was performed on YMC pack ODS AM (150 mm × 4.6 mm, 5 μm) column under gradient conditions with acetonitrile:0.1% formic acid buffer as the mobile phases at a flow rate of 1 ml/min. Precursor ion and product ion transition for analytes and IS were monitored on a triple quadrupole mass spectrometer, operated in the selective reaction monitoring with positive ionization mode. Method was validated over a concentration range of 0.72–183.20 ng/ml for ibrutinib, 0.76–194.33 ng/ml for PCI-45227 and 1.87–479.16 ng/ml for lenalidomide. Mean extraction recovery for ibrutinib, PCI-45227, lenalidomide and IS of 75.2%, 84.5%, 97.3% and 92.3% were consistent across low, medium, and high QC levels. Precision and accuracy at low, medium and high quality control levels were less than 15% across analytes. Bench top, wet, freeze–thaw and long term stability was evaluated for all the analytes. The analytical method was applied to support a pharmacokinetic study of simultaneous estimation of lenalidomide, ibrutinib, and its active metabolite PCI-45227 in Wistar rat. Assay reproducibility was demonstrated by re-analysis of 18 incurred samples. [ABSTRACT FROM AUTHOR]

Highlights: [•] Highly selective method for the determination of ruxolitinib and nilotinib in plasma. [•] This is the first LC–MS/MS-based method for simultaneous determination of ruxolitinib and nilotinib in plasma. [•] Plasma sample clean-up involves a simple protein precipitation procedures. [•] The developed LC–MS/MS based method was applied successfully for pharmacokinetic study. [Copyright &y& Elsevier]

Abstract: A highly selective, sensitive, and robust liquid chromatography–tandem mass spectrometric method for the determination of 5-thio-d-glucose concentrations in rat and human plasma was developed and validated. The sample preparation procedure involved protein precipitation and solid phase extraction, which efficiently removed sources of interference present in the plasma. Chromatographic separation was obtained using an NH2-column with distilled water and acetonitrile as the mobile phase under gradient conditions. Detection was performed using tandem mass spectrometry equipped with an electrospray ionization interface in negative ion mode. The selected reaction monitoring (SRM) transitions for 5-thio-d-glucose and an internal standard (5-thio-d-glucose-13C6) were m/z 195→ m/z 105 and m/z 201→ m/z 108, respectively. The correlation coefficients of the calibration curves ranged from 0.9997 to 0.9999 over a concentration range from 10 to 3000ng/mL plasma. The validated method was successfully applied to a pharmacokinetic study in rats. [Copyright &y& Elsevier]