Cytochrome P-450 catalyzed redox cycling of orthophenylphenol.

o-Phenylphenol was converted to 2,5-dihydroxy biphenyl (phenylhydroquinone) by microsomal P-450. Depending on the cofactor used, microsomal enzymes catalyzed oxidation and/or reduction of phenylhydroquinone. Phenylhydroquinone was oxidized to phenyl 2,5'-p-quinone by cumene hydroperoxide-supported microsomal P-450. Phenyl 2,5'-p-quinone was reduced to phenylhydroquinone by cytochrome P-450 reductase. This study provides direct evidence of cytochrome P-450 catalyzed redox cycling of o-phenylphenol. It is postulated that redox cycling of o-phenylphenol may play a role in o-phenylphenol-caused bladder cancer.