Selective and reliable determination of obacunone in rat plasma using solid‐phase extraction by liquid chromatography tandem mass spectrometry: Application to a pharmacokinetic study

Abstract This study aimed to develop a highly selective, sensitive and fast liquid chromatography tandem mass spectrometric (LC–MS/MS) method for the determination of obacunone in rat plasma. Sample preparation was accomplished by a simple solid‐phase extraction procedure. Chromatographic separation was carried out on an ACQUITY BEH C 18 column using acetonitrile/methanol (1:1, v/v) and 0.1% formic acid in water as mobile phase at a flow rate of 0.4 mL/min. Quantification was performed with multiple reactions monitoring in positive ion mode with the precursor‐to‐product ion transitions at m/z 455.2 > 161.1 for obacunone and m/z 515.2 > 161.1 for nomilin (internal standard). The assay was demonstrated to be linear over the concentration range of 0.1–1,000 ng/mL with correlation coefficient >0.999 ( r > 0.999). The intra‐ and inter‐day accuracy ranged from −8.33 to 10.40%, while the precision was <10.41%. The mean extraction recovery was >75.32%, and the assay was free of matrix effect. The validated LC–MS/MS method was successfully applied to the pharmacokinetic study of obacunone in rats after oral and intravenous administrations. The oral bioavailability of obacunone was 13.59%.