Mutagenicity studies of benzidine and its analogs: Structure-activity relationships

The Ames Salmonella/microsome assay was employed to test the mutagenicity o f benzidine and its analogs using strains TA98 and TA100 in the presence an d absence of Aroclor 1254-induced rat S9 mix. 3,3'-Dichlorobenzidine-2HCl a nd 4,4'-dinitro-2-biphenylamine were directly mutagenic to TA98, while 4,4' -dinitro-2biphenylamine was directly mutagenic to both TA98 and TA100 in th e absence of S9 mix. 2-Aminobiphenyl, 3-aminobiphenyl, and 3,3'-5,5'-tetram ethylbenzidine were not mutagenic in either strains in the presence or abse nce of So. In the presence of S9 mix, 4-aminobiphenyl, benzidine, 3,3'-dich lorobenzidine-2HCl, 3,3'-dimethoxybenzidine, 3,3'-4,4'-tetraaminobiphenyl, o-tolidine, N, N-N', N'-tetramethylbenzidine, and 4,4'-dinitro-2-biphenylam ine were mutagenic to TA98; 4-aminobiphenyl, 3,3'-dichlorobenzidine-2HCl, 3 ,3'-dimethoxybenzidine, and 4,4'-dinitro-2-biphenylamine were mutagenic to TA100. Physicochemical parameters of these compounds including oxidation po tentials, the energy difference between the lowest unoccupied molecular orb ital and the highest occupied molecular orbital, ionization potentials, dip ole moment, relative partition coefficient, and basicity did not correlate with their bacterial mutagenic activities.