Comparative analysis on microbial and rat metabolism of ginsenoside Rb1 by high-performance liquid chromatography coupled with tandem mass spectrometry

Ginsenoside Rb-1 is an active protopanaxadiol saponin from Partax species. In order to compare the similarities and differences of microbial and mammalian metabolisms of ginsenoside Rb-1 the microbial transformation by Acremonium strictum and metabolism in rats were comparatively studied. Microbial transformation of ginsenoside Rb-1 by Acremonium strictum AS 3.2058 resulted in the formation of eight metabolites. Ten metabolites (M1-M10) were detected from the in vivo study in rats and eight of them were identified as the same compounds as those obtained from microbial metabolism by liquid chromatography-tandem mass spectrometry analysis and comparison with reference standards obtained from microbial metabolism. Their structures were identified as ginsenoside Rd, gypenoside XVII, 20(S)-ginsenoside Rg(3), 20(R)-ginsenoside Rg(3), ginsenoside F-2, compound K, 12 beta-hydroxydammar-3-one-20(S)-O-beta-D-glucopyranoside, and 25-hydroxyl-(E)-20(22)-ene-ginsenoside Rg(3), respectively. The structures of the additional two metabolites were tentatively characterized as 20(22),24-diene-ginsenoside Rg(3), and 25-hydroxyginsenoside Rd by HPLC-MS/MS analysis. M7-M10 are the first four reported metabolites in vivo. The time course of rat metabolism of ginsenoside Rb-1 was also investigated. Copyright (c) 2008 John Wiley & Sons, Ltd.