Oleanane-type Saponins from Glochidion hirsutum and Their Cytotoxic Activities

Five new oleanane-type saponins, hirsutosides A-E, were isolated from the leaves of Glochidion hirsutum (Roxb.) VOIGT. Their structures were elucidated as 21 beta-benzoyloxy-3 beta,16 beta,23,28-tetrahydroxyolean-12-ene 3-O-beta-D-glucopyranoside (1),21 beta-benzoyloxy-3 beta,16 beta,23,28-tetrahydroxyolean-12-ene 3-O-beta-D-glucopyranosyl-(1 -> 3)-beta-D-glucopyranoside (2), 21 beta-benzoyloxy-3 beta,16 beta,23,28-tetrahydroxyolean-12-ene 3-O-6-acetyl-[beta-D-glucopyranosyl-(1 -> 3)]-beta-D-glucopyranoside (3), 21 beta-benzoyloxy-3 beta,16 beta,23,28-tetrahydroxyolean-12-ene 3-O-beta-D-glucopyranosyl-(1 -> 3)-<-L-arabinopyranoside (4), and 21 beta-benzoyloxy-3 beta,16 beta,23-trihydroxyolean-12-ene-28-al 3-O-beta-D-glucopyranosyl-(1 -> 3)-alpha-L-arabinopyranoside (5). All isolated compounds were evaluated for cytotoxic activities on four human cancer cell lines, HepG-2, A-549, MCF-7, and SW-626 using the SRB assay. Compounds 1, 2, 4, and 5 showed significant cytotoxic activities against all human cancer cell lines with IC50 values ranging from 3.4 to 10.2 mu m. Compound 3 containing acetyl group at glc C(6 '') exhibited weak cytotoxic activity with IC50 values ranging from 47.0 to 54.4 mu m.