The biotransformation of Bupleuri Radix by human gut microbiota.

1. Bupleuri Radix (BR) is a herbal medicine traditionally used orally in oriental countries, which inevitably comes into contact with the intestinal microbiota. However, whether gut microbiota contribute to the biotransformation of BR, and/or the formation of pharmacologically active compounds remains unknown. 2. In this study, the main saikosaponins (SAPs) of Bupleurum (including saikosaponin a, b1, b2, c, d, f, h) and BR extract (BRE) were individually incubated with human fecal suspensions (HFS), and metabolic time courses of SAPs and their metabolites by human gut bacteria were systematically characterized. 3. Deglycosylation and dehydration were the main metabolic pathways identified for SAPs including newly investigated saikosaponin f (SSf) and saikosaponin h (SSh); dehydration had not been reported previously. A total of 19 dehydrated and deglycosylated metabolites of SAPs were detected and characterized, and 10 of them were newly identified. Moreover, SAPs of BRE were found to be deglycosylated to prosaikogenins. In addition, 13 metabolic pathways related to human gut microbiota were identified for phytochemicals of BRE except for SAPs. Gut microbiota may play a significant role in the biotransformation of BR in humans.