The reaction of sodium nitrite with neurotransmitters secreted in the stomach

Nitroso-compounds are potentially mutagenic and carcinogenic compounds due to their ability to alkylate DNA bases. One of the most common sources of human exposure to nitroso-compounds is their formation in the acidic environment of the stomach by the reaction between electron-rich molecules present in the lumen and sodium nitrite ingested in the diet. To date, the formation of nitroso-compounds by the reaction of nitrite with food components has been investigated in depth, but little attention has been paid to substances secreted in the stomach, such as dopamine or serotonin, whose reaction products with nitrite have proven mutagenic properties. In this article we present a kinetic study with UV-visible spectroscopy of the nitrosation reactions of both molecules, as well as of L-tyrosine, the amino-acid precursor of dopamine. As a result, we have determined their reaction mechanisms, which show that in all of them the favoured reaction product is a stable nitroso-compound and that the molecule whose product is the most mutagenic, serotonin, undergoes two consecutive nitrosation reactions. These findings suggest that more research is needed to understand how this reaction alters the function of these neurotransmitters as well as the potential toxic effects they may have once nitrosated.