A novel bioassay for antioxidant activity based on bactericidal actions of alkyl peroxyl radicals (ROO•) was developed. ROO• was generated by the reaction of heme irons and various alkyl hydroperoxides. A Gram-positive bacterium, Staphylococcus aureus, was subjected to cytotoxic treatment with ROO• with or without various antioxidants. This bacterial suspension was serially diluted, on a 96-well multiplate, in mannitol broth containing phenol red as a pH indicator. After overnight incubation, the growth of ROO•-treated bacteria produces acid, resulting in a change in color of the broth, which permits easy quantitation 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 α-tocopherol, glutathione, l-cysteine, probucol, butylated hydroxyanisole, and butylated hydroxytoluene. Furthermore, the antibactericidal activity of various teas and nonalcoholic drinks showed very high 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 determine ROO•-scavenging activity.
- Alkyl peroxyl radical
- bactericidal action
- peroxyl radical scavenger
ASJC Scopus subject areas
- Agricultural and Biological Sciences(all)