Microbial Transformation of 20(S)-Protopanaxatriol-Type Saponins by Absidia coerulea

Abstract

Three 20(S)-protopanaxatriol-type saponins, ginsenoside-Rg₁ (1), notoginsenoside-R₁ (2), and ginsenoside-Re (3), were transformed by the fungus Absidia coerulea (AS 3.3389). Compound 1 was converted into five metabolites, ginsenoside-Rh₄ (4), 3β,2β,25-trihydroxydammar-(E)-20(22)-ene-6-O-β-d-glucopyranoside (5), 20(S)-ginsenoside-Rh₁ (6), 20(R)-ginsenoside-Rh₁ (7), and a mixture of 25-hydroxy-20(S)-ginsenoside-Rh₁ and its C-20(R) epimer (8). Compound 2 was converted into 10 metabolites, 20(S)-notoginsenoside-R₂ (9), 20(R)-notoginsenoside-R₂ (10), 3β,12β,25-trihydroxydammar-(E)-20(22)-ene-6-O-β-d-xylopyranosyl-(1→2)-β-d-glucopyranoside (11), 3β,12β-dihydroxydammar-(E)-20(22),24-diene-6-O-β-d-xylopyranosyl-(1→2)-β-d-glucopyranoside (12), 3β,12β,20,25-tetrahydroxydammaran-6-O-β-d-xylopyranosyl-(1→2)-β-d-glucopyranoside (13), and compounds 4−8. Compound 3 was metabolized to 20(S)-ginsenoside-Rg₂ (14), 20(R)-ginsenoside-Rg₂ (15), 3β,12β,25-trihydroxydammar-(E)-20(22)-ene-6-O-α-l-rhamnopyranosyl-(1→2)-β-d-glucopyranoside (16), 3β,12β-dihydroxydammar-(E)-20(22),24-diene-6-O-α-l-rhamnopyranosyl-(1→2)-β-d-glucopyranoside (17), 3β,12β,20,25-tetrahydroxydammaran-6-O-α-l-rhamnopyranosyl-(1→2)-β-d-glucopyranoside (18), and compounds 4−8. The structures of five new metabolites, 10−13 and 16, were established by spectroscopic methods.