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首页> 外文学位 >Flavonoid interactions with iron and iron complexes: Implications on in-vitro antioxidant activity.
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Flavonoid interactions with iron and iron complexes: Implications on in-vitro antioxidant activity.

机译：类黄酮与铁和铁络合物的相互作用：对体外抗氧化活性的影响。

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摘要

The ability of iron and iron complexes to promote the reduction of hydrogen peroxide has been known since H. J. H. Fenton's work during the late 19 th century, yet only recently has the role of the so called Fenton reaction in biological systems been recognized. Of particular importance are the conditions surrounding activation or deactivation of the Fenton reaction. Iron complexes of ethylenediaminetetraacetate (EDTA), diethylenetriaminepentaacetate (DTPA), and citrate are thermodynamically capable of hydrogen peroxide reduction, yet the kinetics for the reaction are strongly influenced by the metal to ligand ratio (M:L), so much so in fact that the reaction nearly ceases in the presence of excess ligand. Additionally, the reaction is influenced by a peroxy-Fe-Ligand ternary complex of enhanced Fenton reactivity, the formation of which depends on pH, and relative hydrogen peroxide concentration. A detailed understanding of these observations may shed insight into the mechanism for the effect of certain antioxidants. One such class of antioxidants, the flavonoids, may exert their chemopreventive effects through the chelation of iron. Such action would depend on the stability constant for complex formation between the flavonoid and iron. Of the more than 3000 possible flavonoid compounds, the flavonol class is most often associated with metal chelation. Within this class, there are three possible binding sites. Many flavonoids possess two or three of these possible sites, making chelation studies of these compounds difficult. For this work, 3-hydroxyflavone; 5,7-dihydroxyflavone; and 3 ′4′-dihydroxyflavone; each in possession of only one of the three possible binding sites, are examined for their complexation with ferric iron via potentiometric and spectrophotometric titrations. The data are analyzed through the use of the Hyperquad computer software program, which solves for the stability constants through least squares curve fitting. Flavonoids may also exert an antioxidant effect through interaction with enzymes, in particular, the oxidoreductases. Many of these enzymes are based on the hemo-protein active site which contains a porphyrin macrocycle. The stability constant for the complexation of quercetin to the water-soluble heme-model porphyrin, 5,10,15,20-tetrakis(1-methyl-4-pyridyl)-21H, 23H-porphyrin, both in the presence and absence of ferric iron, are measured by spectrophotometric titration and the Hyperquad software.
机译：自HJH Fenton在19世纪后期开始研究以来，铁和铁络合物促进过氧化氢还原的能力就为人所知，但直到最近才在生物系统中发挥所谓的Fenton反应的作用。被认可。特别重要的是围绕芬顿反应的活化或失活的条件。乙二胺四乙酸盐（EDTA），二亚乙基三胺五乙酸盐（DTPA）和柠檬酸盐的铁络合物在热力学上能够还原过氧化氢，但反应动力学受金属与配体比率（M：L）的强烈影响。在过量配体存在下，反应几乎停止。另外，该反应受芬顿反应性增强的过氧-铁-配体三元配合物的影响，其形成取决于pH和相对过氧化氢浓度。对这些观察结果的详细了解可能有助于洞悉某些抗氧化剂的作用机理。一类这类的抗氧化剂，类黄酮可以通过铁的螯合发挥化学预防作用。这种作用将取决于在类黄酮和铁之间形成络合物的稳定性常数。在3000多种可能的类黄酮化合物中，类黄酮最常与金属螯合有关。在此类中，存在三个可能的结合位点。许多类黄酮具有两个或三个这些可能的位点，使这些化合物的螯合研究变得困难。这项工作是3-羟基黄酮； 5,7-二羟基黄酮;和3 ' 4 '-二羟基黄酮；通过电位滴定法和分光光度滴定法检查每一个只有三个可能结合位点中的一个与铁的络合。通过使用Hyperquad计算机软件程序分析数据，该程序通过最小二乘曲线拟合来求解稳定性常数。类黄酮还可以通过与酶，特别是氧化还原酶的相互作用来发挥抗氧化作用。这些酶中的许多酶都基于包含卟啉大环的血液蛋白活性位点。槲皮素与水溶性血红素型卟啉，5,10,15,20-四（1-甲基-4-吡啶基）-21H，23H-卟啉络合的稳定常数用分光光度滴定法和Hyperquad软件测量三价铁。

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  • 作者

    Engelmann, Mark David.;

  • 作者单位

    University of Idaho.;

  • 授予单位 University of Idaho.;
  • 学科 Chemistry Organic.; Chemistry Biochemistry.
  • 学位 Ph.D.
  • 年度 2003
  • 页码 p.4940
  • 总页数 206
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 有机化学;
  • 关键词

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