Mutagenicity of dibenz[a,c]anthracene and its derivatives in Salmonella typhimurium TA100.

The mutagenic activities of dibenz[a,c]anthracene (DB[a,c]A), and its 11 derivatives, including 3 diols, 6 phenols and 2 oxepines, were studied in the TA100 strain of Salmonella typhimurium at doses varying from 0 to 20 micrograms/plate in the presence of a rat-liver S9 (9000 x g) preparation. Among the diols of DB[a,c]A tested DB[a,c]A-10,11-diol was the most mutagenic compound. However, it was consistently less mutagenic than the parent hydrocarbon. Oxepine-1 and oxepine-2 which are believed to be the photoisomerized products of DB[a,c]A-1,2 oxide and DB[a,c]A-3,4-oxide, respectively, were also less mutagenic than DB[a,c]A. In contrast to these results, 4-hydroxyDB[a,c]A was almost twice as active as DB[a,c]A, and 2-hydroxy- and 3-hydroxyDB[a,c]A were even more (4-6-fold) mutagenic than DB[a,c]A. The remaining phenols were relatively inactive or weakly active in this mutagenicity assay. These results provide initial evidence that the bay-region theory may not be applicable to the mutagenesis of DB[a,c]A, and that the angular ring substituted phenols of DB[a,c]A may be involved in the metabolic activation of this highly mutagenic hydrocarbon.