Microbial transformation of ginsenoside Rb₁ by Rhizopus stolonifer and Curvularia lunata

Of 49 microbial strains screened for their capabilities to transform ginsenoside Rb₁, Rhizopus stolonifer and Curvularia lunata produced four key metabolites: 3-O-[β-D-glucopyranosyl-(1,2)-β-D-glucopyranosyl]-20-O- [β-D-glucopyranosyl]-3β, 12β, 20(S)-trihydroxydammar-24-ene (1), 3-O-[β-D-glucopyranosyl-(1,2)-β-D-glucopyranosyl]-20-O- [β-D-glucopyranosyl]-3β,12β, 20(S)-trihydroxydammar-24-ol (2), 3-O-[β-D-glucopyranosyl-(1,2)-β-D-glucopyranosyl]-3β, 12β, 20(S)-trihydroxydammar-24-ene (3), and 3-O-β-D-glucopyranosyl-3β, 12β, 20(S)-trihydroxydammar-24-ene (4), identified by TOF-MS, ¹H- and ¹³C-NMR spectral data. Metabolites 1, 3 and 4 were from the incubation with R. stolonifer, and 1 and 2 from the incubation with C. lunata. Compound 2 was identified as a new compound.