An antioxidant lignan glycoside and triterpenoid saponins from the leaves of Synsepalum dulcificum

One new lignan glycoside, (+)-(7S,8R,8 ' R)-isolarisiresinol-2 '-O-beta-D-glucopyranoside (1) and one new triterpe-noid saponin, 3-O-(beta-D-xylopyranosyl-(1 -> 3)-beta-D-glucopyranosyl)-protobassic acid methyl ester (2), along with seventeen known triterpenoids and triterpenoid saponins (3-19), were isolated from the leaves of Synsepalum dulcificum. The structures of new compounds were elucidated on the basis of spectroscopic analysis. All com-pounds except 13 were obtained from S. dulcificum for the first time. Most of these compounds were tested for their antioxidant activities by using DPPH free radical and ABTS+ scavenging assays. Compared with positive controls, compound 1 exhibited potent antioxidant activity in DPPH and ABTS+ assays, with IC50 values of 1.19 +/- 0.11 and 5.96 +/- 0.30 mu M, respectively. Compound 7 also displayed antioxidant effects with IC50 values of 8.42 +/- 0.50 and 24.17 +/- 0.83 mu M, respectively, which is comparable to those of vitamin C.