AIM To study the effect of the natural flavonoid
antioxidants 〔green tea polyphenol(GTP),(-) epigallocatechin 3 gallate(EGCG),
quercetin and rutin〕 on the co
oxidation of four compounds (guaiacol, benzidine, p phenylenediamine and o dianisidine) mediated by lipoxygenase for investigating the possibility that the mechanism of their anti oxidation is based on the inhibition of lipoxygenase co oxidation. METHODS The reaction product and free radical intermediate in the reaction medium with or without
antioxidants and other moderators was detected by spectrophotometry and electron spin resonance(ESR). RESULTSGTP, EGCG, quercetin and rutin all reduced the co oxidation reaction rate and the amount of oxidative product and free radical intermediate of the tested four compounds mediated by soybean lipoxygenase(SLO). The 50% inhibition concentration(IC50) of these natural antioxidants for the co oxidation of guaiacol mediated by SLO was 8.2 mg·L-1, 17.4 μmol·L-1, 41.4 μmol·L-1 and 46.1 μmol·L-1, respectively, which was significant lower than reduced glutathion, dl dithiothreitol, butylated hydroxyanisole and gossypol. CONCLUSION GTP, EGCG, quercetin and rutin all can obviously inhibit the co oxidation of four compounds including guaiacol and benzidine catalyzed by SLO.