Oxygen uptake during the mixing of saliva with ascorbic acid under acidic conditions: possibility of its occurrence in the stomach

Abstract

Human saliva, which contains nitrite, is normally mixed with gastric juice, which contains ascorbic acid (AA). When saliva was mixed with an acidic bu¡er in the presence of 0.1 mM AA, rapid nitric oxide formation and oxygen uptake were observed. The oxygen uptake was due to the oxidation of nitric oxide, which was formed by AA-dependent reduction of nitrite under acidic conditions, by molecular oxygen. A salivary component SCN 3 enhanced the nitric oxide formation and oxygen uptake by the AA/nitrite system. The oxygen uptake by the AA/nitrite/SCN 3 system was also observed in an acidic bu¡er solution. These results suggest that oxygen is normally taken up in the stomach when saliva and gastric juice are mixed. ß

Selective and sensitive detection of nitrite based on NO sensing on a polymer-coated rotating disc electrode

“…Taking into account prior dilution, the original content in the saliva sample was calculated to be 130 lM (or ca. 2.8 ppm), which is comparable to other values reported in the literature [24,25,27,28,35]. In order to confirm that there was no interference from the matrix, the centrifuged and diluted saliva samples were spiked with a known quantity of nitrite to evaluate the recovery of the method.…”

“…In the acidic environment nitrite ions are protonized to form nitrous acid (pKa = 3.2-3.4), a species with NO x and NO + donor characteristics [24,25]. The latter might be reduced to NO by any redox system characterized by E 0, lower than E 0, of the NO + /NO transition, which is ca.…”

Reactions of polyphenols in masticated apple fruit with nitrite under stomach simulating conditions: Formation of nitroso compounds and thiocyanate conjugates

“…A portion (about 1 mL) of the apple juice obtained by mastication was passed through the above membrane filter, and the nitrite concentrations were determined using Griess-Romijin reagent as reported previously (Takahama, Hirota, Yamamoto, & Oniki, 2003). To quantify thiocyanate, 1 mL of the apple juice was extracted with 5 mL of ethyl acetate, and the aqueous phase was passed through the above membrane filter.…”

Production of nitric oxide-derived reactive nitrogen species in human oral cavity and their scavenging by salivary redox components

“…Electron spin resonance (ESR) spectra were measured using a JEOL JES-FE1XG spectrometer at about 258C with a quartz flat cell (0.05 ml) under the following conditions as reported previously [14,15]: microwave power, 5 mW; line width, 0.2 mT; amplification, 2000-fold; scanning speed, 5 mT min 21 . The reaction mixture (0.6 ml) was consisted of 0.3 ml of 10 mM sodium phosphate (pH 7.0) containing 5 mM DTCS and 1.5 mM FeCl 3 and 0.3 ml of bacterial fraction prepared for NO detection.…”