STRUCTURAL DETERMINATION OF A MUTAGENIC AMINOPHENYLNORHARMAN PRODUCEDBY THE CO-MUTAGEN NORHARMAN WITH ANILINE

Norharman (9H-pyrido[3,4-b]indole), widely distributed in our environm ent, including cigarette smoke and cooked foodstuffs, is not mutagenic to Salmonella strains, but becomes mutagenic to S.typhimurium TA98 an d YG1024 with S9 mix in the presence of non-mutagenic aromatic amines such as aniline and o-toluidine. To elucidate the mechanisms of co-mut agenicity, we tried to isolate the mutagen(s) produced by a reaction b etween norharman and aniline with S9 mix, By HPLC purification, two mu tagenic compounds (I and II), one (I) showing mutagenicity with and th e other (II) without S9 mix, were isolated. The structure of compound I was deduced to be a coupled compound of norharman and aniline, 9-(4' -aminophenyl)-9H-pyrido[3,4-b] indole (aminophenylnorharman), by a var iety of spectrometry techniques and this was confirmed by its chemical synthesis, The mutagenic activity of this novel heterocyclic amine wa s tested using the pre-incubation method and was found to induce 187 0 00 revertants in TA98 and 1 783 000 revertants in YG1024 per mu g with S9 mix, Compound II was shown to be hydroxyaminophenylnorharman. Form ation of the same DNA adducts was observed in YG1024 when aminophenyln orharman or a mixture of norharman plus aniline was incubated with S9 mix. The hydroxyamino derivative also yielded the same DNA adducts in YG1024, Thus, the appearance of mutagenicity by norharman with aniline in the presence of S9 mix suggests that the coupled mutagenic compoun d, aminophenylnorharman, is formed from norharman and aniline, then co nverted to the hydroxyamino derivative and forms DNA adducts to induce mutations in TA98 and YG1024.