Microbial transformation of ginsenoside Rb1 by Acremonium strictum

Preparative-scale fermentation of ginsenoside Rb-1 (1) with Acremonium strictum AS 3.2058 gave three new compounds, 12 beta-hydroxydammar-3-one-20 (S)-O-beta-D-glucopyranoside (7), 12 beta, 25-dihydroxydammar-(E)-20(22)-ene-3-O-beta-D-glucopyranosyl-(1 -> 2)-beta-D-glucopyranoside (8), and 12 beta, 20 (R), 25-trihydroxydammar-3-O-beta-D-glucopyranosyl-(1 -> 2)-beta-D-glucopyranoside (9), along with five known compounds, ginsenoside Rd (2), gypenoside XVII (3), ginsenoside Rg(3) (4), ginsenoside F-2 (5), and compound K (6). The structural elucidation of these metabolites was based primarily on one- and two-dimensional nuclear magnetic resonance and high-resolution electron spray ionization mass spectra analyses. Among these compounds, 2-6 are also the metabolites of ginsenoside Rb-1 in mammals. This result demonstrated that microbial culture parallels mammalian metabolism; therefore, A. strictum might be a useful tool for generating mammalian metabolites of related analogs of ginsenosides for complete structural identification and for further use in pharmaceutical research in this series of compounds. In addition, the biotransformation kinetics was also investigated.