Pregnane glycosides and steroid saponins from Smilax bockii Warb. and their NGF-potentiating activity

The chemical constituents of the roots of Smilax bockii Warb. were investigated and two pregnane glycosides and three steroid saponins were isolated. Their structures were established as 3beta-hydroxypregna-5,16-dien-20-one-3-O-alpha-L-rhamnopyranosyl(1 --> 4)-alpha-L-rhamnopyranosyl(1 --> 4)-alpha-L-rhamnopyranosyl(1 --> 2)]-beta-D-glucopyranoside (1), 3beta-hydroxypregna-5,16-dien-20-one-3-O-alpha-L-rhamnopyranosyl(1 --> 2)-alpha-L-rhamnopyranosyl(1 --> 4)]-beta-D-glucopyranoside (2), dioscin (3), methyl protodioscin (4), 26-O-beta-D-glucopyranosyl-22alpha-methoxyl-(25R)-furost-5-en-3beta, 26-diol 3-O-alpha-L-rhamnopyranosyl(1 --> 4)-alpha-L-rhamnopyranosyl(1 --> 4)-alpha-L-rhamnopyranosyl(1 --> 2)]-beta-D-glucopyranoside (5) on the basis of spectral analysis and chemical methods. Compound 1 is a new natural product and compounds 2, 5 were first isolated from the genus Smilax. Compound 5 showed enhancing activity of nerve growth factor (NGF)-induced neurite outgrowth in PC 12D cells.