DETERMINATION OF PEROXYL RADICAL-SCAVENGING ACTIVITY IN FOOD BY USINGBACTERICIDAL ACTION OF ALKYL PEROXYL RADICAL

A novel bioassay for antioxidant activity based on bactericidal action s of alkyl peroxyl radicals (ROO(.)) was developed. ROO(.) was generat ed by the reaction of heme irons and various alkyl hydroperoxides. A G ram-positive bacterium, Staphylococcus aureus, was subjected to cytoto xic treatment with ROO(.) with or without various antioxidants. This b acterial suspension was serially diluted, on a 96-well multiplate, in mannitol broth containing phenol red as a pH indicator. After overnigh t incubation, the growth of ROO(.)-treated bacteria produces acid, res ulting in a change in color of the broth, which permits easy quantitat ion of viable bacteria protected by antioxidants. Accordingly, ROO(.) scavenging by various antioxidants could be reproducibly quantitated. Among 22 antioxidants tested, cytotoxicity was substantially inhibited by alpha-tocopherol, glutathione, L-cysteine, probucol, butylated hyd roxyanisole, and butylated hydroxytoluene. Furthermore, the antibacter icidal activity of various teas and nonalcoholic drinks showed very hi gh correlation with their antioxidant activities determined by luminol -dependent chemiluminescence assay (r = 0.91). By this simple bioassay , a large number of samples can be analyzed simultaneously to determin e ROO(.)-scavenging activity.