Elucidation of the Structures of Metabolites of Picroside II in Rat Bile by LC–ESI–IT–MS

Abstract

Picroside II is one of the main active constituents of Picrorhiza kurroa, which has hepatoprotective, anticholestatic, antioxidant, and immune-modulating activity. To gain an understanding of the biotransformation of picroside II in vivo, liquid chromatography–electrospray ionization ion-trap mass spectrometry (LC–ESI–IT–MS) was used to investigate the metabolism of picroside II in rats after intravenous administration of a single dose. This method could simultaneously determine picroside II and its metabolites in rat bile. The bile samples were purified by use of a C18 solid-phase extraction (SPE) cartridge and were separated on a Hypersil ODS2 C18 analytical column. Two phase II metabolites of picroside II in rat bile were characterized, and elucidation of their structures was performed by comparing changes in molecular masses (ΔM), retention times, and MS2 spectral patterns of metabolites with those of the parent drug. Two metabolites identified for the first time in this research were glucuronide and sulfate conjugates.