Kinetic study on 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.

Mutagenic products are promoted in the nitrosation of tyramine.

Tyramine is a biogenic compound derived from the decarboxylation of the amino acid tyrosine, and is therefore present at important concentrations in a broad range of raw and fermented foods. Owing to its chemical properties, tyramine can react with nitrite, a common food additive, in the acidic medium of stomach to form N- and C-nitroso compounds. Since toxicology studies have shown that the product of C-nitrosation of tyramine is mutagenic, in the present article tyramine nitrosation mechanisms have been characterized in order to discern which of them are favoured under conditions similar to those in the human stomach lumen.

Alkylating potential of styrene oxide: reactions and factors involved in the alkylation process.

The chemical reactivity of styrene-7,8-oxide (SO), an alkylating agent with high affinity for the guanine–N7 position and a probable carcinogen for humans, with 4-(p-nitrobenzyl)pyridine (NBP), a trap for alkylating agents with nucleophilic characteristics similar to those of DNA bases, was investigated kinetically in water/dioxane media. UV–vis spectrophotometry and ultrafast liquid chromatography were used to monitor the reactions involved. It was found that in the alkylation process four reactions occur simultaneously: (a) the formation of a β-NBP–SO adduct through an SN2 mechanism; (b) the acid-catalyzed formation of the stable α-NBP–SO adduct through an SN2′ mechanism; (c) the base-catalyzed hydrolysis of the β-adduct, and (d) the acid-catalyzed hydrolysis of SO.

Connecting the chemical and biological reactivity of epoxides.

The chemical reactivity of the mutagenic epoxides (EP) propylene oxide (PO), 1,2-epoxybutane (1,2-EB), and cis- and trans-2,3-epoxybutane (cis- and trans-2,3-EB) with 4-(p-nitrobenzyl)pyridine (NBP), a bionucleophile model for S(N)2 alkylating agents with high affinity for the guanine-N7 position, was investigated kinetically. It was found that three reactions are involved simultaneously: the alkylation reaction of NBP by EP, which yields the corresponding NBP-EP adducts through an S(N)2 mechanism, and EP and NBP-EP hydrolysis reactions. PO and 1,2-EB were seen to exhibit a higher alkylating potential than cis- and trans-2,3-EB.

Taurine-nitrite interaction as a precursor of alkylation mechanisms.

Taurine (2-aminoethanesulphonic acid) is an amino acid-like-compound widely used as an ingredient in some nutraceuticals and energy drinks. Here the interaction of taurine (Tau) with nitrite was investigated. The reactions were carried out mimicking the conditions of the stomach lumen.

DNA-damaging disinfection byproducts: alkylation mechanism of mutagenic mucohalic acids.

Hydroxyhalofuranones form a group of genotoxic disinfection byproduct (DBP) of increasing interest. Among them, mucohalic acids (3,4-dihalo-5-hydroxyfuran-2(5H)-one, MXA) are known mutagens that react with nucleotides, affording etheno, oxaloetheno, and halopropenal derivatives. Mucohalic acids have also found use in organic synthesis due to their high functionalization.

Aromatic C-nitrosation of a bioactive molecule. Nitrosation of minoxidil.

Minoxidil (2,4-diamino-6-(piperidin-1'-yl)pyrimidine N(3)-oxide; CASRN 38304-91-5) is a bioactive molecule with several nitrosatable groups widely used as an antihypertensive and antialopecia agent. Here the nitrosation of minoxidil was investigated. The conclusions drawn are as follows: (i) In the pH = 2.