Free radical scavenging activity of grape seed extract and antioxidants byelectron spin resonance spectrometry in an H2O2/NaOH/DMSO system

The scavenging effects of grape seed extract (GSE) on free radicals formed in an H2O2/NaOH/DMSO system were examined using a spin-trapping electron sp in resonance (ESR) method and compared with other natural antioxidants, asc orbic acid, dl-alpha-tocopherol, and beta-carotene. GSE reduced greatly the ESR signal intensity of superoxide radical-5,5-dimethyl-1-pyrroline-N-oxid e (DMPO) adducts. GSE also exhibited weak scavenging activity on hydroxyl r adical and a little scavenging activity on methyl radical. Ascorbic acid ex hibited strong superoxide and hydroxyl radical scavenging activities, but i t increased the amount of methyl radical at high concentration. dl-alpha-To copherol reduced the amount of superoxide anion, especially the amount of m ethyl radical. However, it slightly reduced the amount of hydroxyl radical. beta-Carotene reduced the amount of hydroxyl radical and methyl radical, b ut it also slightly reduced superoxide anion. In the case of combination us e of beta-carotene and dl-alpha-tocopherol, all radical species were suppre ssed. Combination of GSE and dl-alpha-tocopherol also could reduce all radi cal species. beta-Carotene and dl-alpha-tocopherol could reduce the methyl radical formation induced by ascorbic acid.