Liquid chromatography–tandem mass spectrometry assay for the quantitation of plagiochin E and its main metabolite plagiochin E glucuronides in rat plasma

Plagiochin E, a macrocyclic bisbibenzyl isolated from liverwort Marchantia polymorpha, was found to have antifungal activity. To evaluate the pharmacokinetics of plagiochin E in rats, a sensitive and specific liquid chromatography/tandem mass spectrometric (LC–MS/MS) method was developed and validated for the quantitation of plagiochin E and its total conjugated metabolites in rat plasma. For detection, a Sciex API 4000 LC–MS/MS with a TurboIonSpray ionization (ESI) inlet in the negative ion-multiple reaction monitoring (MRM) mode was used. The plasma samples were pretreated by a simple liquid–liquid extraction with ethyl acetate. The concentration of plagiochin E parent form was determined directly and the concentration of plagiochin E conjugated metabolites was assayed in the form of plagiochin E after treatment with β-glucuronidase/sulfatase. The statistical evaluation for this method reveals excellent linearity, accuracy and precision for the range of concentrations 0.5–1000.0 ng/mL. The method had a lower limit of quantification (LLOQ) of 0.5 ng/mL for plagiochin E in 50 μL of plasma. The method was successfully applied to the characterization of the pharmacokinetic profile of plagiochin E in rats after an oral and an intravenous administration.