Determination and Pharmacokinetic Study of Cyasterone In Rat Plasma after Intravenous Administration by UPLC-MS/MS

Cyasterone is a natural phytoecdysteroid compound extracted from Cyathula officinalis, which is considered as the phytochemical marker for the quality control of the herb in the Chinese Pharmacopoeia. Cyasterone is an insect-metamorphosing substance that has shown significant hormonal activity. In this work, a sensitive and selective UPLC-MS/MS method for determination of cyasterone in rat plasma was developed. After addition of benzoylpaeoniflorin as an internal standard (IS), protein precipitation by acetonitrile-methanol (9: 1, v/v) was used to prepare plasma samples. Chromatographic separation was achieved on a UPLC BEH C18 column (2.1 x 100 mm, 1.7 mu m) with 0.1% formic acid and acetonitrile as the mobile phase with gradient elution. An electrospray ionization source was applied and operated in positive ion mode; multiple reactions monitoring (MRM) mode was used for quantification using target fragment ions m/z 521.3 -> 485.2 for cyasterone, and m/z 607.2 -> 105.1 for benzoylpaeoniflorin (IS). Calibration plots were linear throughout the range 2-1000 ng/mL for cyasterone in rat plasma. Mean recoveries of cyasterone in rat plasma ranged from 75.6% to 84.7%. RSD of intra-day and inter-day precision were both less than 9%. The accuracy of the method was between 96.7% and 106.8%. The method was successfully applied to pharmacokinetic study of cyasterone after intravenous administration in rats.