A fluorimetric and electron spin resonance study of the oxygenation of benzo[a]pyrene; an interpretation of the enzymic oxygenation

Abstract

The oxygenation of benzo[a]pyrene (BP) was examined by treatment with hydrogen peroxide, Fenton's reagent, peroxy-acids, 9,10-diphenylanthracene peroxide (which generates singlet oxygen), and molecular oxygen. Although these reagents were considered to act in different ways, the same oxidation products (BP-3-ol, BP-6-ol, BP-6-oxyl radical, BP-diones, etc.) were produced in the first three systems. The amounts of products, however, depended upon the individual reagents used and also on the reaction conditions. The results are discussed in terms of chemical reactivities, and explain why BP-3-ol but not BP-6-ol is a major metabolite. BP-6-ol, which has not been detected directly as a product of the enzymatic reaction, was formed in the model systems. A mechanism involving direct oxygenation rather than an intermediate arene oxide is postulated.