Enzymatic hydrolysis of the cytotoxic triterpenoid glycoside virgaureasaponin 1

The cytotoxic compound, virgaureasaponin 1, was converted using several optimized enzyme-catalysed hydrolyses to the 28-O-beta-D-xylopyranosyl-(1 --> 4)-alpha-L-rhamnopyranosyl-(1 --> 2)-beta-D-fucopyranoside (2), and the 28-O-alpha-L-rhamnopyranosyl-(1 --> 3)-beta-D-xylopyranosyl-(1 --> 4)-alpha-L-rhamnopyranosyl-(1 --> 2)-beta-D-fucopyranoside (3) and 28-O-beta-D-xylyopyranosyl-(1 --> 4)-alpha-L-rhamnopyranosyl-(1 --> 2)-beta-D-fucopyranoside (4) both lacking the glucose moiety at C-3 of the aglycone. The terminal rhamnose of the acylglycosidic bonded tetrasaccharide was cleaved by naringinase to give compound 2. The new acylglycosides 3 and 4 were obtained with the help of a relatively crude beta-glucuronidase preparation, but the cleavage of the sapogenin bonded glucose was impossible using several beta-glucosidase preparations directly. These derivatives were used for the investigation of the relationship between the saponin carbohydrate structure and their cytotoxic activity. (C) 1998 Elsevier Science Ltd. All rights reserved.