STEROIDAL SAPONINS FROM THE TUBERS OF DICHELOSTEMMA-MULTIFLORUM AND THEIR INHIBITORY ACTIVITY ON CYCLIC-AMP PHOSPHODIESTERASE

Phytochemical examination of the tubers of Dichelostemma multiflorum led to the isolation of three new steroidal saponins together with two known saponins. The structures of the new compounds were determined by spectral data and a few chemical transformations to be (25R)-S alpha-spirostane-1 beta,3 beta-diol (brisbagenin) 1-O-{O-alpha-L-rhamnopyranosyl-(1 --> 3)-4-O-acetyl-alpha-L-arabinopyranoside}, brisbagenin 1-O-{O-alpha-L-rhamnopyranosyl-(1 --> 2)-O-[alpha-L-rhamnopyranosyl-(1 --> 3)]-4-O-acetyl-alpha-L-arabinopyranoside} and (22S,25S)-5 alpha-spirostan-3 beta-ol 3-O-{O-beta-D-galactopyranosyl-(1 --> 2)-O-[beta-D-xylopyranosyl-(1 --> 3)]-O-beta-D-glucopyranosyl-(1 --> 4)-beta-D-galactopyranoside}. The known compounds were identified as desglucolanatigonin II and gitonin, with certain amounts of the corresponding C-25S isomers. Inhibitory activity of the isolated saponins and their derivatives on cAMP phosphodiesterase was evaluated to identify new compounds with medicinal potential.