Rapid quantification of astilbin in rat plasma by liquid chromatography-tandem mass spectrometry and its application to pharmacokinetic study

Astilbin is a potential immunosuppressive agent with minor cytotoxicity. Its oral bioavailability is supposed to be rather low and therefore a sensitive analytical method is required for its pharmacokinetic study after oral administration. A simple, sensitive and rapid liquid chromatography-tandem mass spectrometry(LC-MS/MS) method was developed and validated for the determination of astilbin in rat plasma. Plasma samples were subjected to liquid-liquid extraction with ethyl acetate and separated by reversed phase high performance liquid chromatography(HPLC) with methanol-0.01%(volume fraction) formic acid(50:50, volume ratio) as mobile phase. Quantitive determination was achieved on negative LC-MS/MS by a multiple reaction moitoring method with transitions m/z 449.1→150.9(quantifier) and m/z 449.1→284.9(qualifier) for astilbin and m/z 128.9→42.0 for internal standard(IS). A lower limit of quantification(LLOQ) of ng/mL was achieved within a short cycle time of 3.4 min. The method was successfully applied to a pharmacokinetic study involving oral and intravenous administrations of 6 mg/kg astilbin to six rats.