Two new triterpenoid saponins from Caragana microphylla seeds.

Two new triterpenoid saponins, caraganins A and B (1 and 2), structurally characterized by a 22-oxo group, were isolated from the seeds of Caragana microphylla Lam., together with their n-butyl esters as artifacts (1a and 2a). Their structures and configurations were elucidated by detailed spectroscopic analyses on the basis of NMR, IR, and MS data. Compounds 1a and 2a exhibited potent antibacterial activity against Staphylococcus aureus and Bacillus subtilis with minimum inhibitory concentration values ranging from 3.125 to 6.25 μg/ml.