Oxidation of 2-t-butyl-4-methoxyphenol (BHA) by horseradish and mammalian peroxidase systems

Di-BHA, 2,2'-dihydroxy-3,3'-di-t-butyl-5,5'-dimethoxy-diphenyl, was isolated as the product of the reaction of either commercial horseradish peroxidase or partially purified rat intestine peroxidase (Donor-H₂O₂ oxidoreductase, EC 1.11.1.7.) and hydrogen peroxide with 2-t-butyl-4-methoxyphenol (BHA). BHA, Di-BHA and other cyclic compounds possessing a hydroxyl group in the ring were found to be competitive inhibitors with respect to guaiacol, and non-competitive inhibitors with respect to hydrogen peroxide in a system containing guaiacol, hydrogen peroxide and peroxidase. A free radical intermediate generated during peroxidatic oxidation of BHA was detected and identified by means of EPR spectroscopy. It was estimated that during one hour incubation the peroxidase activity present in the rat ileum mucosa is able to oxidise 12μmoles BHA at a saturating concentration. It is suggested that peroxidative oxidation at the intestinal wall may represent a contribution to the inactivation of some phenol derivatives potentially toxic to mammals.