Regio- and enantioselective oxidation of thiaoleic acids by an algal delta 12-desaturase

Five new spirostanol saponins and a new furostanol saponin were isolated from the fresh bulbs of Lilium candidum. Their structures were elucidated on the basis of spectroscopic analysis, including two-dimensional NMR spectroscopic techniques and the result of acid hydrolysis. The isolated saponins contained a branched triglycoside moiety assigned as O-alpha-L-rhamnopyranosyl-(1-->2)-O-beta-D-glucopyranosyl-(1-->6)]-beta - D-glucopyranose with the formation of an O-glycosidic linkage to C-3 of the aglycone as the common structural feature. The inhibitory activity of the saponins on Na+/K+ ATPase was evaluated.