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Evaluation of oxidative stability of lipids by fluorescence spectroscopy and characterization of flavonoid antioxidant chemistry.

机译：通过荧光光谱和类黄酮抗氧化剂化学表征评估脂质的氧化稳定性。

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摘要

Fluorescence spectroscopy is a sensitive and rapid technique that can be exploited for evaluation of the oxidative stability of lipids. In this study, two assays based on quenching of the fluorescence intensity of an extrinsic probe and an increase in its fluorescence anisotropy due to the free radicals generated during lipid peroxidation were developed for evaluation of antioxidant efficacy and for monitoring the progress of lipid peroxidation. The assays were used to evaluate the efficacies of metal chelating and free radical scavenging antioxidants.;Distinct structure-activity relationships were revealed for the antioxidant activities of flavonoids and isoflavonoids. Presence of electron-withdrawing groups enhanced activity whereas electron-donating groups decreased activity, with the substitution pattern on the B-ring of these compounds being an especially important determinant of activity. Among the isoflavonoids, the biological metabolites of these compounds had similar or superior antioxidant activities in comparison to the parent compounds, a finding that suggests that these compounds may retain their activity under in vivo conditions. An oxidation product of the reaction between the isoflavonoid genistein and peroxyl radicals was characterized and could serve as a marker for genistein antioxidant chemistry.;By use of the assays, the effects of chelators on metal-ion-induced peroxidations were found to be dependent on the type of metal ion used to initiate peroxidation and on the mole ratio of chelator relative to lipid. Flavonoids and isoflavonoids were the class of compounds selected to study prototypic, phenolic free radical scavenging antioxidants. These compounds were more effective at suppressing metal-ion-induced peroxidations than peroxidations induced by free radicals, an indication that metal chelation plays a larger role towards their antioxidant mechanism than has previously been believed. Additionally, fluorescence anisotropy measurements were conducted using a series of probes with the chromophore at varying levels of penetration into the membrane. The results suggest that the flavonoids and isoflavonoids partition preferentially into the hydrophobic interiors of membranes and decrease membrane fluidity in this region. The reduced fluidity could limit accessibility of free radical species generated during lipid peroxidation and stabilize the membrane, a structural mechanism of antioxidant action for these compounds.
机译：荧光光谱法是一种灵敏且快速的技术，可用于评估脂质的氧化稳定性。在这项研究中，开发了两种基于外在探针的荧光强度猝灭和由于脂质过氧化过程中产生的自由基引起的荧光各向异性增加的测定法，用于评估抗氧化剂功效和监测脂质过氧化过程。该方法用于评估金属螯合和清除自由基的抗氧化剂的功效。揭示了类黄酮和异类黄酮的抗氧化活性具有明显的构效关系。吸电子基团的存在增强了活性，而给电子基团的存在降低了活性，这些化合物在B环上的取代模式是活性的特别重要的决定因素。在异类黄酮中，与母体化合物相比，这些化合物的生物代谢产物具有相似或更高的抗氧化活性，这一发现表明这些化合物可能在体内条件下保持其活性。表征了异黄酮类染料木黄酮与过氧自由基之间反应的氧化产物，可以作为染料木黄酮抗氧化剂化学的标志物。通过这些测定，发现螯合剂对金属离子诱导的过氧化反应的影响取决于用于引发过氧化作用的金属离子的类型，以及螯合剂与脂质的摩尔比。类黄酮和异类黄酮是选择用于研究原型酚类自由基清除抗氧化剂的化合物。这些化合物在抑制金属离子诱导的过氧化作用方面比自由基诱导的过氧化作用更有效，这表明金属螯合剂对其抗氧化机理的作用比以前认为的更大。另外，使用一系列探针，发色团以不同的渗透水平进入膜，进行荧光各向异性测量。结果表明，类黄酮和异类黄酮优先分配到膜的疏水内部，并降低该区域的膜流动性。降低的流动性可能会限制脂质过氧化过程中产生的自由基种类的可及性，并使膜稳定，这是这些化合物抗氧化作用的结构机制。

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  • 作者

    Arora, Arti.;

  • 作者单位

    Michigan State University.;

  • 授予单位 Michigan State University.;
  • 学科 Agriculture Food Science and Technology.;Chemistry Analytical.
  • 学位 Ph.D.
  • 年度 1997
  • 页码 207 p.
  • 总页数 207
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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