Biol. Pharm. Bull. 28(10) 1992—1994 (2005)

Araliaceae) has been used as a herbal medicine in China, Korea, Japan and other Asian countries. Its major components are ginsenosides, which are glycosides with a dammarane skeleton. When ginseng is steamed at 98— 100 C, it is called Red Ginseng (RG). Their main components are different: the former is a ginsenoside Rb1, and the latter is a ginsenoside Rg3. These results suggest that the ginsenosides could be easily transformed under steaming. These ginsenosides have been reported to show various biological activities including anti-inflammatory, antiallergic, antitumor, vascular relaxation, and hepatoprotective activities. To express these pharmacological actions, it is thought that ginseng saponins must be metabolized by human intestinal microflora after being taken orally. For example, ginsenosides Rb1, Rb2 and Rc are metabolized to compound K by human intestinal microflora, and the ginsenoside Rg3 is metabolized to ginsenoside Rh2 by human intestinal microflora. The transformed compound K and ginsenoside Rh2 induces an anti-metastatic or anti-carcinogenic effect. However, the relationship between hepatoprotective effects of RG and the metabolism of its main constituent ginsenoside Rg3 have not been thoroughly studied. Therefore, we transformed 20(S)-ginsenoside Rg3 by human intestinal bacteria, isolated its metabolite 20(S)-ginsenoside Rh2, and investigated their hepatoprotective effects on HepG2 cells and mice injured by tert-butyl hydroperoxide (t-BHP).