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Conessine, a steroidal alkaloid obtained from the bark and seeds of the plant species of Apocynaceae family, elicits a histamine antagonistic action, selectively for the H 3 histaminergic receptors. This alkaloid is used mainly for the treatment of dysentery and helminthic disorders. For the quantification of conessine in serum, a liquid chromatography-tandem mass spectrometry method was developed. Chromatographic separation was achieved on a Zorbax SB-CN column (100 × 4.6 mm, 3.5 µm), and a mobile phase consisting of 90% methanol in aqueous ammonium acetate buffer (pH 3.5) with 0.1% (v/v) formic acid at an isocratic flow rate of 0.6 ml/min at 40℃ provides efficiency in separation. A volume of 40 µl was injected each time and the run time for each sample was 5 min. Phenacetin (internal standard) was added to 50 µl of serum sample prior to liquid-liquid extraction using 3% isopropanol in n-hexane. The detection was performed on a 5500 QTRAP mass spectrometer by multiple reaction monitoring mode via electrospray ionization source. The multiple reaction monitoring of conessine and IS was m/ z 357.4 to m/ z 312.1 and m/ z 180.1 to m/ z 138.1, respectively. The method that showed selectivity and linearity in the range of 1-200 ng/ml was validated in terms of sensitivity, accuracy, precision and stability. The detection and quantitation limits were recognized at 0.1 and 1 ng/ml, respectively. The intra- and inter-day precision and accuracy fulfils the acceptance criteria. Applying the method to the pharmacokinetic studies in rats, conessine showed a peak serum concentration at 2 h post oral dose with a good bioavailability of 71.28 ± 4.65%.

Tuberculosis (TB) with human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome represents the most common infectious diseases worldwide. Anti-TB drugs are used concurrently with antiretroviral drug for treatment of TB-HIV co-morbidities. Due to lower risk of interaction with protease inhibitors, rifabutin is preferred over rifampicin in treatment of HIV and TB co-morbidity. A simple and specific liquid chromatography tandem mass spectrometry method was developed for quantification of rifabutin (RBT) and lopinavir (LPV) simultaneously in human plasma. Following extraction using 60% n-hexane in ethyl acetate, the processed samples were chromatographed on a Discovery HS C18 column (5 μm, 50 × 4.6 mm, id) using mobile phase [85% acetonitrile in ammonium acetate buffer (10 mM, pH 4.5)] at a flow rate of 0.7 mL/min. Mass spectrometric detection was performed in positive electrospray ionization mode using multiple reaction monitoring (RBT, m/z 847.7 → 815.4; LPV, m/z 629.6 → 447.4). Raloxifene and phenacetin were used as internal standards for RBT and LPV, respectively. Linearity was established in the range of 1-1,000 ng/mL and 0.5-10 µg/mL (R2 ≥ 0.99) for RBT and LPV, respectively. The recovery of LPV and RBT were always >90 and >50%, respectively. The precisions and accuracies were well within the acceptable limits of variation., (© The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

A rapid, sensitive and simple high-performance liquid chromatography-tandem mass spectrometry method was developed and validated for the quantification of the antileishmanial agent, S010-0269, in hamster serum. A Discovery HS C-18 column (5 μm, 50 × 4.6 mm) maintained at 40°C was utilized for chromatographic separation with mobile phase [acetonitrile: aqueous ammonium acetate (0.01 M) buffer (85:15, v/v)] at a flow rate of 0.6 mL/min. The method requires low serum volume (20 µL) with a run time of 3.5 min. Excellent linear relationships (r ≥ 0.99) were obtained between the measured and added concentration over a range of 1-200 ng/mL. Validation parameters (accuracy, specificity, precision, recovery, matrix effect and stability) were assessed as per FDA guidelines. The precision and accuracy were acceptable as indicated by relative standard deviation ranging from 2.3 to 13.6% and bias values ranging from 1.5 to 6.5%, respectively. Moreover, the compound was found stable in hamster serum even after 30 days of storage at -80°C and being subjected to two freeze-thaw cycles. The validated method was successfully applied to the pharmacokinetic study after 10 mg/kg oral dose of S010-0269 in hamsters., (© The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Ormeloxifene (ORM) is a non-steroidal, selective estrogen receptor modulator used as a once a week oral contraceptive and is intended for long-term clinical use by females. Therefore, a simple, sensitive and rapid LC-MS/MS method was developed and validated for simultaneous quantification of ORM and its active metabolite (7-desmethyl ormeloxifene, 7-DMO) in rat plasma. Also, the method was partially validated in human plasma. Chromatographic separation was achieved on Discovery HS C-18 column (5μm, 50×4.6mm) with mobile phase [acetonitrile: aqueous ammonium acetate (0.01M) buffer (85: 15, %v/v)] at a flow rate of 0.8mL/min. The calibration curve was linear (r≥0.99) for a concentration range of 0.78-100ng/mL for both the analytes. The precision (%RSD; ORM, 1.3 to 13.4; 7-DMO, 3.1 to 15.0) and accuracy (%bias; ORM, -13.8 to 12.5; 7-DMO, -10.6 to 6.8) in both rat and human plasma were within the acceptable limits. The recovery for ORM and 7-DMO was always >79.1% and >72.9%, respectively. Both the analytes were found stable in rat plasma even after 30 days of storage at -80°C and on being subjected to three freeze-thaw cycles. The method has not only short run time (3.5min) but requires a low plasma sample volume (20μL) and is the first reported LC-MS/MS method for simultaneous quantification of the marketed drug known as centchroman (INN: ormeloxifene) and the metabolite 7-DMO in plasma. The method was applied to evaluate drug-drug interaction of ORM with the commonly prescribed antidepressant drug sertraline using serial sampling in rats., (Copyright © 2015 Elsevier B.V. All rights reserved.)

A reversed phase liquid chromatography tandem mass spectrometry method was developed and validated for quantification of cardamonin, a potential anticancer chalcone, in rat serum. Curcumin was used as an internal standard. Following liquid-liquid extraction using n-hexane and ethyl acetate (60:40, v/v), the processed samples were chromatographed on a C18 column using acetonitrile and ammonium acetate buffer (0.01 M, pH 4.5) (85:15, v/v) as mobile phase at a flow rate of 0.6 mL min(-1). Mass spectrometric detection was performed in the negative electrospray ionization mode by multiple reaction monitoring (m/z 269→122 and 367→217 for cardamonin and curcumin, respectively). The method was validated in terms of selectivity, accuracy, precision, sensitivity, reproducibility, dilution integrity and stability. The linearity was established in the range of 1-200 ng mL(-1) (r≥0.999). The recovery of cardamonin from spiked serum was always >90%. The intra- and inter-day precision (%RSD) and accuracy (%bias) were well within the acceptable limits. The method was applied for single oral and intravenous dose pharmacokinetics in male and female Sprague Dawley rats. Following oral dose, cardamonin showed peak serum concentration that occurred at ∼2 h with very low bioavailability in both male (0.6%) and female (4.8%) rats. Cardamonin exhibited a significant gender influence on pharmacokinetics and bioavailability in rats., (Copyright © 2015 Elsevier B.V. All rights reserved.)

An approach has been developed for the quantitative determination of concentrations of centchroman (I), a nonsteroidal once-a-week oral contraceptive, and its major metabolite (7-desmethyl centchroman, II) using dried blood spots (DBS) on paper, rather than conventional plasma samples. The assay employed simple solvent extraction of the DBS sample circle (6 mm) requiring small blood volumes (30 μL) followed by reversed-phase HPLC separation, combined with multiple reaction monitoring mass spectrometric detection. The calibration plot in matrix using d-trans-hydroxy chroman as internal standard (IS) was linear (r²  = 0.998) over ranges of 1.5-240 and 4.5-720 ng/mL for I and II, respectively. The recoveries of both I and II were always >60% with quantification limits (signal-to-noise ratio = 10) of 1.5 and 4.5 ng/mL for I and II, respectively. The intra-day and inter-day precision (%RSD) and accuracy (%bias) variations in blood spots for both I and II were better than 13%. Moreover, both I and II were stable in DBS for at least 3 months when stored at room temperature. The developed method was successfully applied to the pharmacokinetic interaction study after oral administration of centchroman with and without co-administration of carbamazepine in female Sprague-Dawley rats using serial sampling and results were comparable with the plasma concentrations reported earlier., (Copyright © 2011 John Wiley & Sons, Ltd.)