Combined reversed-phase and normal-phase high-performance liquid chromatography in the purification and identification of 7,12-dimethylbenz[a]anthracene metabolites.

A total of 37 compounds have been identified as rat liver microsomal metabolites of the potent carcinogen 7,12-dimethylbenz[a]anthracene and its hydroxymethyl derivatives 7-methyl-12-hydroxymethylbenz[a]anthracene, 7-hydroxymethyl-12-methylben[a]anthracene and 7,12-dihydroxymethylbenz[a]anthracene. The metabolites were characterized by: (i) retention times on reversed-phase (with a C18 column) and normal-phase (with a silica gel column) high-performance liquid chromatography (HPLC); (ii) ultraviolet absorption and fluorescence spectra; (iii) mass spectral analysis; (iv) optical activity; and (v) comparison of the physicochemical properties of the metabolites with those of some available synthetic standards. The 37 identified metabolites include four trans-3,4-dihydrodiols, four trans-5,6-dihydrodiols, four trans-8,9-dihydrodiols, four trans-10,11-dihydrodiols, two methyl carboxylic acids, two methyl aldehydes, two hydroxymethyl aldehydes, four 2-phenols, four 3-phenols, four 4-phenols and three hydroxymethyl derivatives. The trans configuration of the dihydrodiols was determined by their inability to form vicinal cisacetonides. Seven dihydrodiol metabolites were found to be optically active. Detailed physicochemical properties, such as ultraviolet absorption spectra, fluorescence spectra measured in methanol and in 0.1 N NaOH, major mass ions from mass spectral analysis and the retention times on two HPLC systems, are presented in support of the structural assignments.