SAPONINS FROM STEM BARK OF PETERSIANTHUS-MACROCARPUS

Two bioactive saponins were isolated from the stem bark of Petersianthus macrocarpus. Their structures were elucidated by chemical degradations and by a combination of 2D NMR techniques and by Californium plasma desorption mass spectrometry. They are 3-O-[beta-D-galactopyranosyl (1 --> 2)][beta-D-galactopyranosyl (1 --> 3)]-beta-D-glucuronopyranosyl}-21-O-[3-(3-tigloyloxynilic acid)-4-tigloyloxy-alpha-L-arabinopyranosyl] barringtogenol C and 3-O-{[beta-D-galactopyranosyl (1 --> 2)] [beta-D-galactopyranosyl (1 --> 3)]-beta-D-glucuronopyranosyl}-28-O-alpha-L-rhamno-pyranosyl barringtogenol C-21-O-benzoate. The absolute configuration of nilic acid was determined by partial synthesis. 3,3'-Dimethoxy ellagic acid and 3,3'-dimethoxy-4-0-beta-D-glucopyranosyl ellagic acid were also isolated.