Chemiluminescence from Acetaldehyde Oxidation by Xanthine Oxidase Involves Generation of and Interactions with Hydroxyl Radicals

The ability of acetaldehyde to generate free radicals is often ascribed to its oxidation by xanthine oxidase, with the subsequent production of reactive oxygen intermediates. Chemiluminescence associated with the oxidation of acetaldehyde by xanthine oxidase was inhibited by superoxide dismutase, catalase, or several hydroxyl radical scavenging agents, and was stimulated by the addition of EDTA or ferric-EDTA. This suggests that the light emission is primarily due to the production of hydroxyl radicals via an iron-catalyzed Haber-Weiss type of reaction. Chemiluminescence with hypoxanthine as substrate for xanthine oxidase was much lower than that found with acetaldehyde, yet rates of hydroxyl radical production were greater with hypoxanthine. Acetaldehyde increased light emission in the presence of hypoxanthine by a greater than additive effect. These results suggest a complex role for acetaldehyde in catalyzing xanthine oxidase-dependent chemiluminescence. It appears that besides being a substrate for xanthine oxidase, acetaldehyde also reacts with the generated hydroxyl radical to produce acetaldehyde radicals, which yield chemiluminescence upon their decay. Further studies will be required to evaluate whether the production of such species contributes to or plays a role in the generation of reactive oxygen intermediates and toxicity associated with acetaldehyde metabolism.