Recently identified nitrite-reactive compounds in food: occurrence and biological properties of the nitrosated products.

Various Japanese foodstuffs are directly-acting mutagens in Salmonella typhimurium TA100 after nitrite treatment. Such mutagen precursors include tyramine and beta-carboline derivatives, isolated from soya sauce, and indole-3-acetonitrile, 4-methoxyindole-3-acetonitrile and 4-methoxyindole-3-aldehyde, isolated from fresh Chinese cabbage. A mutagen produced from tyramine with nitrite was found to be 4-(2-aminoethyl)-6-diazo-2,4-cyclohexadienone (3-diazotyramine), and one produced from indole-3-acetonitrile with nitrite to be 1-nitrosoindole-3-acetonitrile. These two mutagens were directly-acting mutagens not only in S. typhimurium TA100 and TA98 but also in Chinese hamster lung cells, using diphtheria toxin resistance as a selective marker. The carcinogenicity of 3-diazotyramine was demonstrated in male Fischer 344 rats. Tyramine, beta-carboline and indole compounds are present ubiquitously in our environment, especially in foods. Therefore, the role of these newly identified mutagen precursors in the development of human cancer should be taken into consideration.