On the Nature of Biochemically Generated Hydroxyl Radicals Studies using the Bleaching of p‐Nitrosodimethylaniline as a Direct Assay Method

Abstract

An efficient scavenger for radiolytically generated hydroxyl (.OH) radicals, p-nitrosodimethylaniline, was used to try to substantiate the presence of this oxygen radical species in several biochemical systems [autoxidation of epinephrine, 6-hydroxydopamine and hydroquinone, the NADH/phenazine methosulfate hydroxylating system, oxidation of dihydrofumaric acid, oxidation of xanthine or acetaldehyde by xanthine oxidase]. Most of these systems investigated had previously been assumed to generate .OH radicals. No inhibition of the bleaching of p-nitrosodimethylaniline in oxygenated solutions by other scavengers of .OH radicals nor, in the case of xanthine/xanthine oxidase, by catalase and superoxide dismutase was observed. Under biochemical conditions as opposed to radiolysis or photolysis, no freely diffusable .OH radicals are apparently formed. Rather, a strongly oxidizing .OH-analogous complex probably represents the p-nitrosodimethylaniline-detectable species formed under these conditions.