Mutagenicity of some synthetic quinolines and quinoxalines related to IQ, MeIQ or MeIQx in Ames test

3-Methyl- and 3,4-dimethyl-3H-imidazo4,5-f]quinoline, 3,8-dimethyl-3H-imidazo4,5-f]quinoxaline, N6-methyl- and N6,7-dimethylquinoline-5,6-diamine, as well as N6,3-dimethylquinoxaline-5,6-diamine, have been synthesized. Only the first-mentioned compound was active in Ames test; the response was equal for Salmonella typhimurium TA98 and TA100, regardless of enzymatic activation (S9). However, its mutagenicity to TA98 + S9 was 300-1300 times smaller than the values reported for the related compounds, 3-methyl- and 3,4-dimethyl-3H-imidazo4,5-f]quinolin-2-amine ('IQ' and 'MeIQ'), and for 3,8-dimethyl-3H-imidazo4,5-f]quinoxalin-2-amine ('MeIQx'). Hence, the presence of the imidazole ring and the 2-amino group in the molecule seems to be important for the high mutagenicity of the latter compounds.