Fungal oxidation of (+/-)-9,10-dihydroxy-9,10-dihydrobenzo[a]pyrene: formation of diastereomeric benzo[a]pyrene 9,10-diol 7,8-epoxides.

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Abstract
The filamentous fungus Cunninghamella elegans oxidized [the carcinogen] (.+-.) trans-9,10-dihydroxy-9,10-dihydrobenzo[a]pyrene to a complex mixture of metabolites which were detected by high-pressure liquid chromatography. Two of the metabolites were identified as (.+-.)-7.beta.,8.alpha.,9.alpha.,10.beta.-tetrahydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene and (.+-.)-7.beta.,8.alpha.,9.beta.,10.alpha.-tetrahydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene. A 3rd product gave absorption and mass spectra consistent with a diol-epoxide structure. Hydrolysis of this compound gave [.+-.]-7.beta.,8.alpha.,9.beta.,10.alpha.-tetrahydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene as the major identifiable product with a minor unidentified tetraol. Synthetic [.+-.]-9.alpha.,10.beta.-dihydroxy-7.beta.,8.beta.-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene gave the same hydrolysis products and had the same retention time on high-pressure liquid chromatography as did the fungal metabolite. The trans-9,10-dihydroxy-9,10-dihydrobenzo[a]pyrene recovered at the end of the experiment showed no optical activity, indicating that both enantiomers were metabolized by the fungus. C. elegans apparently oxidizes [.+-.]-trans-9,10-dihydroxy-9,10-dihydrobenzo[a]pyrene to diastereomeric benzo[a]pyrene 9,10-diol 7,8-epoxides. [The similarity of metabolites produced by C. elegans to those produced by mammalian liver was discussed.].

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