All rights of reproduction in any form reserved. MOLECUI.AR PHARMACOLOGY, 32:710-722 Reglo- and Stereoselective Metabolism of Dibenz[a,h]anthracene: Identification of 1 2 New

Incubation of the carcinogenic polycyclic aromatic hydrocarbon dibenz[a,h]anthracene (DBA) with liver microsomes of Sprague-Dawley rats, pretreated with Aroclor 1 254, yielded more than 30 metabolites. Fifteen of these could be identified, and they ac-count for 95 % of the ethyl acetate-extractable metabolites of DBA. Twelve metabolites were identified for the first time, by chromatographic and spectroscopic methods: these were DBA-5,6-oxide, 1-, 2-, 3-, 4-, 5-, 6-phenols, 3,4:12,13-bis-dihydrodiol, 1,4/2,3-tetrol, 1,3/2,4-tetrol, 3,4-catechol, and a phenol dihydro-diol derived from the 2-phenol. Quantitative determination re-vealed that the attack of cytochrome P-450 dependent monoox-ygenases occurs at the 1 2-, 3,4- and 5,6-positions of the DBA molecule in the ratio 1.7:1.9:1.0. Evidence is presented which indicates that the phenols of DBA are formed by aromatization of the initially generated arene oxides, rather than by direc