Ames mutagenicity of 15 aryl, benzyl, and aliphatic ring N-nitrosamines

The Ames mutagenicity test is an effective means of screening compounds for their carcinogenic potential. Here, we conducted Ames tests on 15 aryl, benzyl, and aliphatic ring N-nitrosamines. Then, by using two indicators of mutagenicity strength calculated from the Ames test results, namely, maximum specific activity (MSA; number of revertant colonies) and maximum fold increase (MFI; relative ratio of increased colonies), we examined the relationship between Ames mutagenicity strength and Carcinogenic Potency Categorization Approach (CPCA) potency category, which is a structure-activity-relationship-based prediction of the carcinogenic potency of nitrosamines. Eleven of the test compounds were Ames positive and four were negative. Of the 11 positive compounds, three were categorized as strong positive (MSA ≥1000), five as medium positive (100 ≤ MSA <1000), and three as weak positive (MSA <100). The compounds with an aliphatic ring showed a negative relationship between mutagenicity strength (i.e., MSA or MFI) and carcinogenic potential (i.e., CPCA category), whereas, the alpha-methyl aryl N-nitrosamines did not. Overall, MSA and MFI were found to be detailed indicators of the carcinogenic potency of the N-nitrosamines and can potentially be used to support CPCA categorization.