Reactions of thiocyanate in the mixture of nitrite and hydrogen peroxide under acidic conditions: investigation of the reactions simulating the mixture of saliva and gastric juice.

Nitrite and SCN(-) in saliva can mixes with H(2)O(2) in the stomach. The mixing can result in the formation of ONOOH. It is not yet known how salivary SCN(-) reacts with ONOOH. An objective of the present study was to elucidate the reaction between ONOOH and SCN(-). In nitrite/H(2)O(2) systems at pH 2, SCN(-) inhibited the consumption of nitrite and the formation of O(3)(-). SCN(-) enhanced the decomposition of ONOOH and H(2)O(2) in HNO(2)/H(2)O(2) systems. Accompanying the reactions, sulfate was formed, suggesting that ONOOH oxidized SCN(-). SCN(-) inhibited the nitration of phenolics induced by HNO(2)/H(2)O(2). The inhibition is discussed taking SCN(-)-dependent reduction of ONOOH to HNO(2) into consideration. SCN(-) also inhibited H(2)O(2)-induced consumption of nitrite and nitration of phenolics in acidified saliva. The result obtained in this study suggests that salivary SCN(-) can reduce ONOOH to O(2)(-)/HNO(2) inhibiting nitrating reactions in the stomach.