The microbiological transformation of steroidal saponins by Curvularia lunata

The microbiological transformation of polyphyllin I (compound ), polyphyllin III (compound ), polyphyllin V (compound ) and polyphyllin VI (compound ) by Curvularia lunata into their corresponding subsaponins, for example, diosgenin-3-O-α-l-arabinofuranosyl (1→4)-β-d-glucopyranoside (compound ), diosgenin-3-O-α-l-rhamnopyranosyl (1→4)-β-d-glucopyranoside (compound ), diosgenin-3-O-β-d-glucopyranoside (compound ) and pennogenin-3-O-β-d-glucopyranoside (compound ), were studied in this paper. Curvularia lunata is able to hydrolyze terminal rhamnosyls that are linked by 1→2 C– bond to sugar residues of steroidal saponins at C-3 position with high activity and regioselectivity.