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Determination of swertianolin in rat plasma by LC-MS/MS and its application to a pharmacokinetic study.

A sensitive and rapid LC-MS/MS method has been developed and validated for quantifying swertianolin in rat plasma using rutin as an internal standard (IS). Following liquid-liquid extraction with ethyl acetate, chromatographic separation for swertianolin was achieved on a C18 column with a gradient elution using 0.1% formic acid as mobile phase A and acetonitrile as mobile phase B at a flow rate of 0.3 mL/min. The detection was performed on a tandem mass spectrometer using multiple reaction monitoring via an electrospray ionization source and operating in the negative ionization mode. The optimized mass transition ion pairs (m/z) for quantitation were 435.1/272.0 for swertianolin and 609.2/300.1 for IS. The lower limit of quantitation was 0.5 ng/mL within a linear range of 0.5-500 ng/mL. Intra-day and inter-day precision was less than 6.8%. The accuracy was in the range of -13.9 to 12.0%. The mean recovery of swertianolin was >66.7%. The proposed method was successfully applied in evaluating the pharmacokinetics of swertianolin after an oral dose of 50 mg/kg Swertia mussotii extract in rats.