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Fukuoka, Japan

Kaempferol glycosides can be hydrolyzed to their aglycone kaempferol during cooking under acidic conditions and in the oral cavity and the intestine by glycosidases. Kaempferol was oxidised by nitrite under acidic conditions (pH 2.0) to produce nitric oxide (NO), and the nitrite-induced oxidation of kaempferol was enhanced and inhibited by 10 and 100 mg of starch ml 1, respectively. The opposite effects of starch were discussed by considering the binding of kaempferol to starch and starch-dependent inhibition of the accessibility of nitrous acid to kaempferol. Kaempferol inhibited α-amylase-catalysed starch digestion by forming starch/kaempferol complexes, and the inhibitory effects increased in the order of amylopectin < soluble starch < amylose. The different effects of kaempferol were discussed to be due to the difference in binding sites of kaempferol between amylose and amylopectin. From the present study, dual-function of kaempferol became apparent in the digestive tract. © 2013 Elsevier Ltd. All rights reserved.

Hirota S.,Kyushu Womens University | Takahama U.,Kyushu University
Food Science and Technology Research | Year: 2014

Apple fruit (cultivar sunfuji) contained procyanidin B2, (-)-epicatechin, and chlorogenic acid as major polyphenols. The concentration increased in the order procyanidin B2 < (-)-epicatechin < chlorogenic acid. Nitrite reacted with the polyphenols in methanol extracts of apple fruit both in an acidic buffer solution (pH 2.0) and at the pH of acidified saliva. The rate of the reaction increased in the order chlorogenic acid < (-)-epicatechin < procyanidin B2. During the reactions, nitrous acid (pKa = 3.3) was reduced to nitric oxide (NO) by the polyphenols, and nitroso compounds of procyanidin B2 and (-)-epicatechin were produced. Our conclusion are that (i) the nitroso compounds can be produced by the reaction of NO with radicals of procyanidin B2 and (-)-epicatechin, which are formed by the nitrous acid-dependent oxidation of procyanidin B2 and (-)-epicatechin, and that (ii) polyphenols such as chlorogenic acid and (-)-epicatechin, which will react with nitrous acid slowly in the gastric lumen, can be transported to the intestine when apple is ingested. Copyright © 2014, Japanese Society for Food Science and Technology.

Takahama U.,Kyushu Dental College | Hirota S.,Kyushu Womens University
Chemical Research in Toxicology | Year: 2010

The pH in dental plaque falls to below 5 after the ingestion of foods, and it may remain low if acid-tolerant bacteria grow in the plaque. Certain nitrate-reducing bacteria in the oral cavity can proliferate in dental plaque at low pH, and nitrite is detected in such plaque. In acidic dental plaque, NO2 can be produced by self-decomposition of nitrous acid and also by peroxidase-catalyzed oxidation of nitrite, and it may oxidize uric acid, a major antioxidant in the oral cavity. Under experimental conditions that simulate oral cavity, the oxidation of uric acid by nitrite and by nitrite/peroxidase systems was much more rapid at pH 5 than at pH 7, suggesting the more rapid production of NO2 in dental plaque at lower pH. We propose that if the pH of plaque developed in a dental crevice decreased, NO2 and other nitrogen oxides produced in the plaque would diffuse into the adjoining gingival tissues. The results of this study seem to contribute to the understanding of the induction of periodontal diseases in the context of nitrite-dependent production of nitrogen oxides in acidic dental plaque. © 2010 American Chemical Society.

Takahama U.,Kyushu Dental College | Tanaka M.,Kyushu Dental College | Hirota S.,Kyushu Womens University
Plant Foods for Human Nutrition | Year: 2010

Buckwheat flour, which is used for various dishes in the world, is a good source of proanthocyanidins. Proanthocyanidins in the buckwheat flour reduced nitrous acid producing nitric oxide (NO) when the flour was suspended in acidified saliva or in acidic buffer solution in the presence of nitrite. The ingestion of dough prepared from buckwheat flour increased the concentration of NO in the air expelled from the stomach, suggesting that the proanthocyanidins also reduced nitrite to NO in the stomach. During the production of NO by the buckwheat flour/nitrous acid systems, oxidation, nitration, and nitrosation of proanthocyanidins proceeded. The increase in the concentration of NO could improve the activity of stomach helping the digestion of ingested foods and the nitration and nitrosation of the proanthocyanidins could contribute to the scavenging of reactive nitrogen oxide species generated from NO and nitrous acid. © Springer Science+Business Media, LLC 2009.

Iron(III) ingested as a food component or supplement for iron deficiencies can react with salivary SCN - to produce Fe(SCN) 2+ and can be reduced to iron(II) by ascorbic acid in the stomach. Iron(II) generated in the stomach can react with salivary nitrite and SCN - to produce nitric oxide (NO) and FeSCN +, respectively. The purpose of this investigation is to make clear the reactions among nitrite, SCN -, iron ions, and ascorbic acid under conditions simulating the mixture of saliva and gastric juice. Iron(II)-dependent reduction of nitrite to NO was enhanced by SCN - in acidic buffer solutions, and the oxidation product of iron(II) reacted with SCN - to produce Fe(SCN) 2+. Almost all of the NO produced was autoxidized to N 2O 3 under aerobic conditions. Iron(II)-dependent production of NO was also observed in acidified saliva. Under anaerobic conditions, NO transformed Fe(SCN) 2+ and FeSCN + to Fe(SCN)NO + in acidic buffer solutions. Fe(SCN)NO + was also formed under aerobic conditions when excess ascorbic acid was added to iron(II)/nitrite/SCN - systems in acidic buffer solutions and acidified saliva. The Fe(SCN)NO + formed was transformed to Fe(SCN) 2+ and iron(III) at pH 2.0 and pH 7.4, respectively, by O 2. Salivary glycoproteins could complex with iron(III) in the stomach preventing the formation of Fe(SCN) 2+. Ascorbic acid reduced iron(III) to iron(II) to react with nitrite and SCN - as described above. The above results suggest (i) that iron(II) can have toxic effects on the stomach through the formation of reactive nitrogen oxide species from NO when supplemented without ascorbic acid and through the formation of both reactive nitrogen oxide species and Fe(SCN)NO + when supplemented with ascorbic acid, and (ii) that the toxic effects of iron(III) seemed to be smaller than and similar to those of iron(II) when supplemented without and with ascorbic acid, respectively. Possible mechanisms that cause oxidative stress on the stomach through Fe(SCN)NO + are discussed. © 2011 American Chemical Society.

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