New Triterpenoid Saponins from Glochidion eriocarpum and Their Cytotoxic Activity

Combined chromatographic methods led to the isolation of two new triterpenoid saponins, glochieriosides A and B (1,2), from the aerial parts of Glochidion eriocarpum, along with three known triterpenes, glochidone (3), lup-20(29)-en-3β,23-diol (4), and lup-20(29)-en-1β,3β-diol (5). The structures of the new saponins were determined to be 22β-benzoyloxy-3β,16β,28-trihydroxyolean-12-ene 3-O-[β-D-glucopyranosyl-(1→3)-α-L-arabinopyranoside] (1) and 22β-benzoyloxy-3β,16β,28-trihydroxyolean-12-ene 3-O-[β-D-glucopyranosyl-(1→3)-β-D-xylopyranoside] (2). The structural elucidation was accomplished by using a combination of the 1D-NMR (1^H-, ^<13>C-NMR, distortionless enhancement by polarization transfer (DEPT) 90°, and DEPT 135°), 2D-NMR (1^H-1^H correlation spectroscopy, heteronuclear multiple quantum correlation, heteronuclear multiple bond correlation, and rotating frame Overhouser effect spectroscopy), ESI-MS, and HR-FAB-MS experiments. Glochieriosides A and B exhibited significant cytotoxic activity against HL-60, HT-29, MCF-7 and SK-OV-3 human cancer cell lines with the IC_<50> values of 5.5, 6.8, 29.1, and 22.7μM for glochierioside A, respectively, and 6.6, 18.6, 36.1, and 16.0μM for glochierioside B. Glochidone was less active with IC_<50> values greater than 100μM while lup-20(29)-en-1β,3β-diol was moderately active with IC_<50> values of 43.3, 67.0, 66.1, and 48.0μM, respectively.