Superoxide anion and hydroxyl radical scavenging activities of vegetable extracts measured using electron spin resonance

Radical scavenging by reconstituted lyophilized powders of water extracts f rom 16 common vegetables was measured using electron spin resonance (ESR) w ith 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), hydroxyl radicals, (. OH) or s uperoxide anion radicals (O2(.-)), as DMPO-OH or DMPO-OOH spin adducts. On a dry weight basis, eggplant, and red, yellow and green bell pepper extract s showed potent superoxide anion radical scavenging activities (SOD-like ac tivities). Ascorbate oxidase- or heat-treatments, decreased SOD-like activi ties in bell pepper extracts suggesting that ascorbate accounts for much of their free radical scavenging activity. Eggplant epidermis extract exhibit ed the most potent hydroxyl radical scavenging and SOD-like activities. Egg plant SOD-like activity did not decrease after ascorbate oxidase treatment, but decreased following ultrafiltration demonstrating that SOD-like activi ty is partially due to high molecular weight substances. Nasunin, an anthoc yanin in eggplant epidermis, showed markedly potent superoxide anion radica l scavenging activity, while it inhibited hydroxyl radical generation proba bly by chelating ferrous ion.