Abstract
Human intestinal bacteria hydrolyze ginsenosides, triterpenoid glycosides of Panax ginseng C. A. MEYER (Araliaceae) to the active metabolites. M1 (20S-protopanaxadiol 20-O-β-D-glucopyranoside) is the final metabolite of protopanaxadiol-type ginsenosides. In the present study, we explored the dominant bacterial species involved in metabolism of ginsenosides by means of M1-producing activity assay and terminal restriction fragment length polymorphism (T-RFLP) analysis. Results from M1-producing activity assay of fecal specimens from 17 adults revealed remarkable individual differences in the activity. T-RFLP patterns of 16S ribosomal DNA (rDNA) PCR products from 5 of the 17 specimens, which showed the ability to produce M1, showed that the genus Bacteroides spp. were present among M1-producers. Then, type strains of the genus Bacteroides spp. including B. acidofaciens, B. caccae, B. fragilis, B. intestinalis, B. ovatus, B. stercoris, B. thetaiotaomicron, B. uniformis and B. vulgatus were assayed for M1-producing activity. All the strains tested, except B. uniformis JCM 5825T, produced no or less M1. Moreover, 11 reference strains of B. uniformis also produced M1. These results suggest that B. uniformis may act as the dominant bacterial species capable of producing M1 in human intestines.
