Department of Physical Chemistry, Faculty of Pharmacy, University of Granada, 18071 Granada, Spain.
Talanta. 2003 Jun 13;60(2-3):609-16. doi: 10.1016/S0039-9140(03)00191-7.
Much work has been carried out in recent years on the beneficial effect of phenolic compounds as natural antioxidants which help to neutralize free radicals. In fact, researchers have focused their attention on the pathological role of free radicals in a variety of diseases, among which the most important are atherosclerosis and cancer. Thus, among the components of the so-called 'Mediterranean Diet', phenolic compounds have received increased attention as epidemiological studies have shown that consumption of foods and beverages rich in phenolics is correlated with reduced incidence of heart disease. In this study, four phenolic compounds: (1) 3,4,5-trihydroxybenzoic acid (gallic acid); (2) trans 3,4',5-trihydroxystilbene (trans-resveratrol); (3) 3,3',4',5,7-pentahydroxyflavone (quercetin) and its glycoside (4) 3,3',4',5,7-pentahydroxyflavone-3-rutinoside (Rutin) have been subjected to antioxidant study by a fluorimetric assay. In this method, the rate of peroxidation induced by 2,2'-azobis (2-methylpropionamidine) dihydrochloride was monitored through the loss of fluorescence of the protein B-phycoerythrin (B-PE). Under appropriate conditions, the loss of B-PE fluorescence in the presence of reactive species is an index of oxidative damage of the protein. The inhibition of the action of reactive species by phenolic compounds, reflected in the protection against the loss of B-PE fluorescence in the fluorimetric assay, is a measure of its antioxidant capacity against the reactive species. The antioxidant effects of phenolic compounds have been investigated at different concentrations to relate activity to structural effects. It has been observed that the fluorescence decay due to peroxyl radical attack on B-PE decreases exponentially with time. As a reference compound for antioxidant capacity we used 6-hydroxy-2,5,7,8-tetramethyl-chroman-2-carboxylicacid (trolox), a water soluble tocopherol analogue. This compound reacts rapidly with peroxyl radicals, and, until the trolox is consumed, no loss in phycoerythrin fluorescence is observed. A linear correlation of the net protection value with the concentration of trolox was demonstrated. The phenolic compounds studied react with peroxyl radicals in a similar way to trolox. Quercetin and rutin were shown to have strong antioxidant activities. The results obtained here are in agreement with previous studies confirming that quercetin is the most antioxidant of the four polyphenolics.
近年来，人们对酚类化合物作为天然抗氧化剂的有益作用进行了大量研究，这些化合物有助于中和自由基。事实上，研究人员已经将注意力集中在自由基在各种疾病中的病理作用上，其中最重要的是动脉粥样硬化和癌症。因此，在所谓的“地中海饮食”的成分中，酚类化合物受到了更多的关注，因为流行病学研究表明，食用富含酚类化合物的食物和饮料与心脏病发病率的降低有关。在这项研究中，四种酚类化合物：（1）3,4,5-三羟基苯甲酸（没食子酸）；（2）反式 3,4',5-三羟基二苯乙烯（反式白藜芦醇）；（3）3,3',4',5,7-五羟基黄酮（槲皮素）及其糖苷（4）3,3',4',5,7-五羟基黄酮-3-芸香糖苷（芦丁），通过荧光分析法进行了抗氧化研究。在该方法中，通过 2,2'-偶氮（2-甲基丙脒）二盐酸盐诱导的过氧化物的损失来监测蛋白质 B-藻红蛋白（B-PE）的荧光损失。在适当的条件下，在存在反应性物质的情况下 B-PE 荧光的损失是蛋白质氧化损伤的指标。酚类化合物对反应性物质的作用的抑制，反映在荧光分析中对 B-PE 荧光损失的保护作用中，是其对反应性物质的抗氧化能力的衡量标准。研究了不同浓度的酚类化合物的抗氧化作用，将活性与结构效应联系起来。已经观察到，由于过氧自由基攻击 B-PE 而导致的荧光衰减随时间呈指数下降。作为抗氧化能力的参考化合物，我们使用了 6-羟基-2,5,7,8-四甲基-色满-2-羧酸（trolox），一种水溶性生育酚类似物。该化合物与过氧自由基迅速反应，并且，在 trolox 消耗之前，没有观察到藻红蛋白荧光的损失。证明了净保护值与 trolox 浓度之间的线性相关性。研究的酚类化合物以与 trolox 相似的方式与过氧自由基反应。槲皮素和芦丁表现出很强的抗氧化活性。这里得到的结果与以前的研究一致，证实槲皮素是这四种多酚中抗氧化能力最强的。
