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Formic acid (0.1–0.2‰) in the mobile phase overcame the matrix effects and increased the sensitivity of MS detection of euscaphic acid.

BackgroundGalangin (3,5,7-trihydroxyflavone) is present in high concentrations in herbal medicine such as Alpinia officinarum Hance. Galangin shows multifaceted in vitro and in vivo biological activities. The number and position of hydroxyl groups in this molecule play an important role in these biological activities. However, these hydroxyl groups undergo glucuronidation and sulfation in in vitro assay system. However, the systemic exposure to galangin after dosing in animals and/or humans remains largely unknown. Thus it is not clear whether the galangin exists in the body at concentrations high enough for the biological effects. Furthermore, the metabolite identification and the corresponding plasma pharmacokinetics need to be characterized.ResultsTwo LC-MS/MS methods were developed and validated and successfully applied to analyze the parent drug molecules and aglycones liberated from plasma samples via β-glucuronidase hydrolysis. Our major findings were as follows: (1) The routes of administration showed significant influences on the systemic exposure of galangin and its metabolites. (2) Galangin was preferentially glucuronidated after p.o. dosing but sulfated after i.v. medication. (3) Kaempferol conjugates were detected demonstrating that oxidation reaction occurred; however, both glucuronidation and sulfation were more efficient. (4) Oral bioavailability of free parent galangin was very low.ConclusionsSystemic exposure to galangin and its metabolites was different in rat plasma between oral and intravenous administration. Further research is needed to characterize the structures of galangin conjugates and to evaluate the biological activities of these metabolites.Graphical abstractGalangin was preferentially glucuronidated after p.o. dosing but sulfated after i.v. medication.

The evaluation of efficacy and safety should be paralleled with the assessment of comprehensive pharmacokinetic (PK) properties for a drug candidate, and a robust bioanalytical method is a prerequisite for obtaining PK information. a-Hederin is reported to have various in vitro and in vivo activities; however, very little is known about its PK and metabolic characteristics. In this study, we have developed an efficient LC-ESI(À)-MS/MS assay for a-hederin and its sapogenin hederagenin in rat plasma. Sample cleanup involved methanol precipitation for identification analysis and liquid-liquid extraction with ethyl acetate for quantification assay. LC analysis was performed under reversed-phase conditions in the modified "pulse gradient elution" mode. Analyte identification and quantification were conducted using multiple reaction monitoring (MRM) mode with euscaphic acid as the internal standard. Under these conditions, deglycosylated metabolites and their sulfate conjugates were detected; however, hederagenin was not detected in rat plasma samples after both oral and intravenous treatments. The mean plasma clearance (CL), volume of distribution (V SS ) and elimination half-life (t 1/2 ) of a-hederin were 0.24 L h À1 kg À1 , 0.25 L kg À1 and 2.67 h, respectively. The oral bioavailability (F) of a-hederin in rats was about 0.14%, which might result from the poor intestinal absorption and/or extensive biliary excretion. It is hoped that this validated method will be useful for future PK studies of a-hederin.