The dual function of nitrite under stomach conditions is modulated by reducing compounds

Salivary nitrite plays a role in the lipid peroxidation process of muscle tissue in simulated gastric fluid. The objectives of our study were to elucidate the fate of nitrite in the presence of reducing compounds and to evaluate its effect on lipid peroxidation during digestion. Nitrite at pH 3 (possibly NO₂{radical dot}, not NO{radical dot}) can oxidize β-carotene, but the addition of reducing compounds, ascorbic acid or polyphenols, alters its effect. Ascorbic acid alone promoted the formation of NO{radical dot} from nitrite only up to pH 3, but the addition of iron ions facilitated the formation of NO{radical dot} up to pH 5.5. NO{radical dot} prevented membranal lipid peroxidation under stomach conditions. Nitrite, only in the presence of reducing compounds, achieved the same goal but at much higher concentrations. Addition of polyphenols to nitrite synergistically improved its antioxidant effect. Therefore, to promote NO{radical dot} production and to achieve better control of the lipid peroxidation process in the stomach, a nitrite-rich meal should be consumed simultaneously with food rich in polyphenols.