Triterpenes possessing an unprecedented skeleton isolated from hydrolyzate of total saponins from Gynostemma pentaphyllum

Five novel triterpenes were isolated from hydrolyzate of total saponins from Gynostemma pentaphyllum and identified as gypensapogenin A (1), gypensapogenin B (2), gypensapogenin C (3), 3-O-β-d-glucopyranosyl-gypensapogenin D (4) and gypensapogenin D (5), two of which (1 and 2) possess unprecedented ring A. The cyclization of the side chains-3 formed five-membered cyclic ketone rings similar to ring E in 1. The 21-oic acid-21, 23-lactone was...