Scammonins VII and VIII, two resin glycosides from Convolvulus scammonia.

Two minor ether-soluble resin glycosides, scammonins VII and VIII, were isolated from Radix Scammoniae, the roots of Convolvulus scammonia. In addition to (2S)-2-methylbutyric acid and tiglic acid, they are composed, respectively, of orizabic acid A and a new glycosidic acid named scammonic acid B, with similar macrocyclic ester structures to those of the scammonic acid A-based scammonins I-VI. Isolation of genuine scammonins III-V, which were previously obtained as peracetates, is also described.