Quercetin-dependent inhibition of nitration induced by peroxidase/H2O2/nitrite systems in human saliva and characterization of an oxidation product of quercetin formed during the inhibition
Quercetin-dependent inhibition of nitration induced by peroxidase/H2O2/nitrite systems in human saliva and characterization of an oxidation product of quercetin formed during the inhibition
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DOI：
10.1021/jf0404389
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发表时间：
2005-05-04
影响因子：
6.1
通讯作者：
Yamauchi, R
中科院分区：
文献类型：
--
作者：
Hirota, S;Takahama, U;Yamauchi, R
在产酸细菌增殖的部位，口腔中的局部pH值可以降低到7以下。用透析人唾液研究了pH对4-羟基苯乙酸硝化反应的影响。在亚硝酸盐和H2 O2存在下，透析唾液将4-羟基苯乙酸硝化为4-羟基-3-硝基苯乙酸。硝化速率取决于pH，在pH 5.5和7.2之间观察到最大速率。最佳pH值似乎反映了二氧化氮和4-羟基苯乙酸自由基的形成速率。槲皮素抑制硝化反应。槲皮素依赖的抑制作用可能是通过清除NO2和4-羟基苯乙酸自由基，而NO2和4-羟基苯乙酸自由基分别由唾液过氧化物酶依赖的氧化亚硝酸盐和4-羟基苯乙酸形成，并与唾液中的过氧化物酶竞争。槲皮素在抑制硝化反应的过程中生成氧化产物。氧化产物鉴别为2-（3，4-二羟基苯甲酰基）-2，4，6-三羟基-3（2 H）-苯并呋喃酮。该组分也可被唾液过氧化物酶和二氧化氮自由基氧化。氧化产物为2，4，6-三羟基苯乙醛酸和3，4-二羟基苯甲酸。在此基础上，讨论了槲皮素抑制口腔中二氧化氮生成和清除二氧化氮自由基的意义。
Local pH in the oral cavity can decrease to below 7 at the site where acid-producing bacteria are proliferating. Effects of pH on nitration of 4-hydroxyphenylacetic acid were studied using dialyzed human saliva. Dialyzed saliva nitrated 4-hydroxyphenylacetic acid to 4-hydroxy-3-nitrophenylacetic acid in the presence of nitrite and H2O2. The rate of the nitration was dependent on pH, and the maximal rate was observed between pH 5.5 and 7.2. The optimum pH seemed to reflect rates of formation of nitrogen dioxide and 4-hydroxyphenylacetic acid radicals. Quercetin inhibited the nitration. The quercetin-dependent inhibition might be due to scavenging of nitrogen dioxide and 4-hydroxyphenylacetic acid radicals, which were formed by salivary peroxiclase-depenclent oxidation of nitrite and 4-hydroxyphenylacetic acid, respectively, and competition with nitrite and 4-hydroxyphenylacetic acid for peroxidase in saliva. An oxidation product of quercetin was formed during inhibition of the nitration by quercetin. The oxidation product was identified as 2-(3,4-dihydroxybenzoyl)-2,4,6-trihydroxy-3(2H)-benzofuranone. This component could also be oxidized by salivary peroxidase and nitrogen dioxide radicals. The oxidation products were 2,4,6-trihydroxyphenylglyoxylic and 3,4-dihydroxybenzoic acids. On the basis of the results, the significance of quercetin for inhibition of nitrogen dioxide formation and for scavenging of nitrogen dioxide radicals in the oral cavity is discussed.