In vitro antioxidant properties of a ginseng intestinal metabolite IH-901.

IH-901 (20-O-β-D-glucopyranosyl-20(S)-protopanaxadiol or compound K) is a final intestinal bacterial metabolite of ginseng in humans. It has various pharmacologic effects such as antiaging, immunopotentiation, antistress, and antimetastatic activities. We analyzed the antioxidant activities of IH-901 using several assays including: total antioxidant activity, reductive potential, 1,1-diphenyl-2-picryl-hydrazyl, hydroxyl, superoxide and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging assays, a nitric oxide scavenging assay and a lipid peroxidation assay. At concentrations of 25 and 100 µg/mL, IH-901 inhibited lipid peroxidation of a linoleic acid emulsion with a potency comparable to ascorbic acid and butylated hydroxyanisole. The reductive potential of IH-901 increased in a concentration-dependent manner. IH-901 exhibited strong DPPH, hydroxyl, superoxide and ABTS radical scavenging activities. IH-901 was also an effective inhibitor of lipid peroxidation, although IH-901 had only a mild scavenging activity against nitric oxide. These results suggest that IH-901 may be a useful antioxidant agent against reactive oxygen species.