T. Kaneyuki et al., Superoxide anion and hydroxyl radical scavenging activities of vegetable extracts measured using electron spin resonance, BIOC MOL B, 47(6), 1999, pp. 979-989
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.