Reduction of benzydamine N-oxide by rat liver xanthine oxidase.

Abstract

Evidence is presented that a purified xanthine oxidase preparation, like milk xanthine oxidase, is responsible for the xanthine-dependent reduction of benzydamine N-oxide. Rat liver preparations contain enzymes which catalyze the anaerobic reduction of benzydamine N-oxide by either reduced nicotinamide adenine dinucleotide (phosphate) NAD (P) H or xanthine. In crude enzyme preparations, the enzymatic reduction seems to involve xanthine oxidase and/or cytochrome P-450 because allopurinol, an inhibitor of xanthine oxidase, and n-octylamine, an inhibitor of aliphatic tertiary amine N-oxide reductase (cytochrome P-450) block the reduction of benzydamine N-oxide in crude enzyme preparations of rat liver. Moreover, the enzymatic system exhibited dual pH optima of 7.4 and 9.0 for reductions dependent on NADPH and xanthine, respectively. An enzyme preparation which did not contain cytochrome P-450 was isolated from rat liver and purified 186-fold in terms of xanthine oxidase activity. Xanthine oxidase activity and xanthine-dependent benzydamine N-oxide reduction activity were copurified in parallel.