Steroidal saponins from the bulbs of Lilium speciosum x L. nobilissimum 'Star Gazer' and their antitumour-promoter activity.

The fresh bulbs of the oriental hybrid lily, Lilium speciosum x L. nobilissimum 'Star Gazer' yielded a new steroidal saponin, (25R,26R)-26-methoxyspirost-5-en-3 beta-ol 3-O-[O-alpha-L-rhamnopyranosyl-(1-->2)-O-[6-O-acetyl-beta-D-glucopyranos yl- (1-->4)]-beta-D-glucopyranoside], along with four known steroidal saponins, (25R,26R)-26-methoxyspirost-5-en-3 beta-ol 3-O-[O-alpha-L-rhamnopyranosyl-(1-->2)-O-]beta-D-glucopyranosyl-(1-->4)] - beta-D-glucopyranoside], (25R)-27-O-[(S)-3-hydroxy-3-methylglutaryl]- spirost-5-ene-3 beta, 27-diol 3-O-[O-alpha-L-rhamnopyranosyl-(1-->2)-beta-D- glucopy-ranoside] and (25R)-27-O-[(S)-3-hydroxy-3-methylglutaryl]- spirost-5-eene-3 beta, 27-diol 3-O-[O-alpha-L-rhamnopyranosyl-(1-->2)-O- O-[beta-D-glucoyranosyl-(1-->4)]-beta-D-glucoyranoside]. The structure of The structure of the new saponin was determined by means of spectroscopic analysis and hydrolysis. The methyl ester of 5 showed potent inhibitory activity on 12-O-tetradecanoylphorbol-13-acetate (TPA)-stimulated 32P incorporation into phospholipids of HeLa cells.