Effects of the Interaction of Tannins with Co-existing Substances. VI. Effects of Tannins and Related Polyphenols on Superoxide Anion Radical, and on l,l-Diphenyl-2-picrylhydrazyl Radical

Abstract

The scavenging effects of twenty-five tannins including low-molecular polyphenols on the superoxide anion radical (CV) generated in the hypoxanthine-xanthine oxidase system were estimated by electron spin resonance (ESR) measurements of the adducts formed by 5,5-dimethyl-l-pyrroline-A^-oxide (DMPO) and the radical. The scavenging effects of tannins and related polyphenols having orf/ro-trihydroxyl (pyrogallol) structure [galloyl, hexahydroxydiphenoyl (HHDP) groups in hydrolyzable tannins, galloyl group in acylated proanthocyanidins, and the B-ring of some flavan-3-ols] were stronger than the effects of unacylated proanthocyanidins. The effects of tannins and related polyphenols on the superoxide anion radical were also compared with those on the l,l-diphenyl-2-picrylhydrazyI (DPPH) radical. Each tannin in an ethanol solution of DPPH radical reduced the intensity of the signal of the DPPH radical, and gave a weak signal assignable to a radical derived from that tannin, in a similar way to the appearance of the signal of