New antibacterial triterpenoid saponin from Lactuca scariola.

A new antibacterial triterpenoid saponin, 3beta-O-[alpha-L-rhamnopyranosyl]-30-norolean-12,19-diene-28-oic acid 28-O-[beta-D-glucopyranosyl-(1-->4)-O-beta-D-galactopyranosyl]-ester (1); has been isolated from the stems of Lactuca scariola. Its structure was determined by chemical degradations and spectral analysis.