Structure and Mutagenicity of a Direct-Acting Mutagen Derived from the Reaction of N-Nitroso-N-methylbutylamine with Hydroxyl Radical

The mutagenicity of N-nitrosamines is usually detected in the presence of an S9 mix, which includes cytochrome P450.The mutagenicity of N-nitrosodialkylamines is induced by Fe 2+ -Cu 2+ -H 2 O 2 , which can be used as a chemical model for cytochrome P450.However, a direct-acting mutagen derived from N-nitroso-N-methylbutylamine (NMB) by the same oxidation system has not been reported.In this study, we determined the structure of a direct-acting mutagen obtained from the reaction of NMB with Fe 2+ -Cu 2+ -H 2 O 2 by comparing its instrumental data ( 1 H, 13 C NMR and IR) with that from the synthesized compound.We confirmed that the direct-acting mutagen derived from NMB with Fe 2+ -Cu 2+ -H 2 O 2 was 5-methyl-5-nitro-1-pyrazoline 1-oxide.Furthermore, we investigated the mechanism of the mutagenicity by 5-methyl-5-nitro-1-pyrazoline 1-oxide using Salmonella typhimurium strains.The mutagenicity of 5-methyl-5-nitro-1-pyrazoline 1-oxide in S. typhimurium YG7108, which is deficient O 6 -alkylguanine alkyltransferase, was higher than that in the parent strain S. typhimurium TA1535, indicating that the mutations are caused by DNA alkylation.