The formation of dihydrodiols from benzo[alpha]pyrene by oxidation with an ascorbic acid/ferrous sulphate/EDTA system

In the oxidation of benzo[alpha]pyrene in an abscorbic acid-ferrous sulphate-EDTA system, four dihydrodiols were detected. Three, trans-4,5-dihydro-4,5-dihydroxybenzo[alpha]pyrene, trans-7,8-dihydro-7,8-dihydroxybenzo[alpha]pyrene and trans-9,10-dihydro-9,10-dihydroxybenzo[alpha]pyrene were identified by their UV spectra and by direct comparisons of their chromatographic properties, using HPLC, with those of the authentic compounds. The fourth compound appeared to be trans-11,12-dihydro-11,12-dihydroxybenzo[alpha]pyrene since its ultraviolet spectrum was identical to that of the cis-dihydrodiol. Time-course experiments showed that the maximum amounts of products were obtained after 8 h of oxidation. A re-examination of the dihydrodiols formed from benzo[alpha]pyrene by rat-liver microsomal fractions failed to show the formation of the trans-11,12-dihydrodiol.