Triterpene saponins from Vietnamese ginseng (Panax vietnamensis) and their hepatocytoprotective activity

The methanol extract of Vietnamese ginseng (Panax vietnamensis) was found to possess hepatocytoprotective effects on D-galactosamine (D-GalN)/tumor necrosis factor-alpha (TNF-alpha)-induced cell death in primary cultured mouse hepatocytes. Further chemical investigation of the extract afforded two new dammarane-type triterpene saponins, ginsenoside Rh-5 (1) and vina-ginsenoside R-25 (2), as well as eight known dammarane-type triterpene saponins, majonoside R-2 (3), pseudo-ginsenoside RT4 (4), vina-ginsenosides R-1 (5), R-2 (6), and R-10 (7), ginsenosides Rg(1) (8), Rh-1 (9), and Rh-4 (10), and a known sapogenin protopanaxatriol oxide II (11). Their structures were elucidated on the basis of spectral analysis. In addition, by the using LC-electrospray ionization (ESI)-MS method, five known saponins, ginsenosides Rb-1, Rb-2, Re, Rd, and Re (12-16), were also identified in the extract. Among the compounds isolated, majonoside R-2 (3), the main saponin in Vietnamese ginseng, showed strong protective activity against D-GalN/TNF-alpha -induced cell death in primary cultured mouse hepatocytes. This demonstrates that the hepatocytoprotective effect of Vietnamese ginseng is due to dammarane-type triterpene saponins that have an ocotillol-type side chain. a characteristic constituent of Vietnamese ginseng.