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.     

15N chemically induced dynamic nuclear polarization during reaction of N-acetyl-L-tyrosine with the nitrating systems nitrite/hydrogen peroxide/horseradish peroxidase and nitrite/hypochloric acid

While the Maillard reaction of amino acids and proteins as well as its consequences in vivo has been thoroughly investigated, little attention has so far been paid to the glycation of aminophospholipids such as phosphatidylethanolamine (PE) or phosphatidylserine (PS), which are essential for structure and functionality of biological membranes. PE-derived glucosylamines (Schiff-PEs) and aminoketoses (Amadori-PEs) have now for the first time been simultaneously identified and quantified in erythrocytes from diabetics and healthy individuals by liquid chromatography-electrospray mass spectrometry (LC-(ESI)MS). The amounts of glycated PE (gPE) were significantly higher in diabetics (0.18-34.2 mol% Schiff-PE and 0.047-0.375 mol% Amadori-PE) than in controls (0.12-3.99 mol% Schiff-PE and 0.018-0.055 mol% Amadori-PE). A positive correlation between fructosylated hemoglobin (HbA(1c)) and the gPE levels was established. No advanced glycation endproducts (AGEs) like 5-hydroxymethylpyrrole-2-carbaldehyde (pyrrole-PE), carboxymethyl (CM-PE), or carboxyethyl (CE-PE) derivatives were detected. To investigate the influence of gPE on lipid peroxidation of biological membranes, liposomes consisting of soy-PE and synthetically prepared Amadori-PE (16:0-16:0) were incubated for several days and the formation of oxidation products was monitored. It could be shown that Amadori-PE extensively promotes lipid peroxidation even in the absence of transition metal ions like Cu(2+) and Fe(3+). Oxidative damage to membrane lipids therefore is supposed to be at least partially caused by the glycation of aminophospholipids.     

A novel mutagen, 2-(5-hydroxy-4,6-dinitroindolyl) ethanol, formed in the reaction between 5-hydroxytryptamine and nitrite under acid conditions, especially in the presence of l-cysteine

We examined the mutagenic activity of each of 29 amino acids mixed under acidic conditions with 5-hydroxytryptamine (5-HT) and nitrite using Salmonella typhimurium strain TA 100 with or without a metabolic activation system (S9 mix). The reaction mixture containing l-cysteine was strongly mutagenic without S9 mix. We subjected an ethyl acetate extract of the reaction mixture to HPLC, isolated a mutagenic component, and investigated its chemical structure by LC–mass spectrometry (MS), high-resolution fast atom bombardment (HRFAB)-MS, and ¹H and ¹³C NMR. We identified the mutagen as 2-(5-hydroxy-4,6-dinitro-3-indolyl) ethanol (2HDIE). We injected 8 mg/kg 2HDIE i.p. into male ICR mice and found that the compound increased the frequency of micronuclei in peripheral reticulocytes. Our results suggest that 2HDIE might be formed in vivo by consumption of 5-HT, nitrite and l-cysteine in foods, and might act as a mutagen.