Quantification of β-eudesmol in rat plasma using LC-MS/MS and its application to a pharmacokinetic study

A sensitive and specific LC-MS/MS assay for determination of β-eudesmol in rat plasma was developed and validated. After liquid-liquid extraction with ethyl ether, the analyte and IS were separated on a Capcell Pak C₁₈ column (50 × 2.0 mm, 5 μm) by isocratic elution with acetonitrile-water-formic acid (77.5:22.5:0.1, v/v/v) as the mobile phase at a flow rate of 0.4 mL/min. An ESI source was applied and operated in positive ion mode; a selected reaction monitoring scan was used for quantification by monitoring the precursor-product ion transitions of m/z 245.1 → 163.1 for β-eudesmol and m/z 273.4 → 81.2 for IS. Good linearity was observed in the concentration range of 3-900 ng/mL for β-eudesmol in rat plasma. Intra- and inter-day precision and accuracy were both within ±14.3%. This method was applied for pharmacokinetic studies after intravenous bolus of 2.0 mg/kg or intragastric administration of 50 mg/kg β-eudesmol in rats.