ENZYMATIC-HYDROLYSIS OF THE CYTOTOXIC TRITERPENOID GLYCOSIDE VIRGAUREASAPONIN-1

The cytotoxic compound, virgaureasaponin 1, was converted using severa l optimized enzyme-catalysed hydrolyses to the 28-O-beta-D-xylopyranos yl-(1 --> 4)-alpha-L-rhamnopyranosyl-(1 --> 2)-beta-D-fucopyranoside ( 2), and the 28-O-alpha-L-rhamnopyranosyl-(1 --> 3)-beta-D-xylopyranosy l-(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 cr ude beta-glucuronidase preparation, but the cleavage of the sapogenin bonded glucose was impossible using several beta-glucosidase preparati ons directly. These derivatives were used for the investigation of the relationship between the saponin carbohydrate structure and their cyt otoxic activity. (C) 1998 Elsevier Science Ltd. All rights reserved.