Antioxidant and free radical-scavenging activity of Choto-san and its related constituents

The antioxidant properties of Choto-san and its related constituents such as Chotoko and Choto-san without Chotoko, and phenolic compounds contained in Chotoko such as epicatechin, caffeic, acid and quercetin were evaluated. In the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging assay, the scavenging activity of Chotoko (IC50 14.3 mug/ml) was found to be higher than that of Choto-san (IC50 206.2 mug/ml) and Choto-san without Chotoko (IC50 244.3 mug/ml). Epicatechin (IC50 10.4 muM), caffeic acid IC50 13.8 mug/ml), and quercetin IC50 7.1 muM) also revealed scavenging activity against DPPH radicals. Choto-san IC50 67.7 mug/ml) exhibited stronger inhibitory activity against superoxide anion formation than Choto-san without Chotoko IC50 92.4 mug/ml) but weaker activity than Chotoko IC50 18.3 mug/ml). The generation of superoxide anion was also inhibited by epicatechin IC50 175.2 muM), caffeic acid (IC50 141.7 muM), and quercetin (IC50 18.7 muM). In a hydroxyl radical-scavenging experiment, Choto-san IC50 2.4 mg/ml), Chotoko IC50 2.2 mg/ml), Choto-san without Chotoko (IC50 2.8 mg/ml), epicatechin IC50 3.9 mm), caffeic acid (IC50 3.6 mm), and quercetin UC50 1.9 mm) exhibited activity. In NG108-15 cells, when added simultaneously with H2O2 (500 muM), Choto-san (250 mug/ml), Chotoko (250 mug/ml), Choto-san without Chotoko (500 mug/ml), epicatechin (200 muM), caffeic acid (200 muM), and quercetin (200 muM) effectively protected cells from oxidative damage. In conclusion, the present results provide evidence that Choto-san acts as an antioxidant and cytoprotective agent against oxidative damage, which is due at least partly to the phenolic compounds contained in Chotoko.