4种异黄酮抗氧化活性的构效关系

Structure-Activity Relationship of Four Isoflavones for Scavenging Free Radicals Evaluated by Quantum Chemistry Calculation

为探究异黄酮类化合物抗氧化活性的构效关系,以染料木素、大豆苷元、橙桑黄酮、奥沙京4种异黄酮类分子为代表展开研究。测定了4种分子的体外抗氧化活性,并与文献报道进行分析比对。对4种分子进行分子模拟,得到稳定的优势构象并对其进行相关量子化学计算。结果分析表明,4种异黄酮分子清除自由基能力与其酚羟基位置电子转移和脱氢能力有关,前线分子轨道能直观地展现抗氧化物的分子活性部位,而能隙和自由基生成热能准确表征4种异黄酮分子抗氧化活性顺序,对于4种分子的多羟基位自由基生成热分析可知,4’-OH是染料木素和大豆苷元最主要的羟基活性部位,3’-OH是橙桑黄酮和奥沙京最主要的羟基活性部位,4’-OH和3’-OH可分别作为表征这4种分子清除自由基活性的位点。

Isoflavones are a large class of polyphenols with biological activity. They are currently the subject of extensive research for their significant antioxidant activity. This investigation determined and compared the in vitro antioxidant activity of genistein, daidzein, pomiferin and osajin isoflavones as representative isoflavones with reported data in the literature and further explored their structure-activity relationships for 1,1-diphenyl-2-picrylhydrazyl（DPPH） scavenging capacity and oxygen radical absorbance capacity（ORAC）. Molecular simulation of the four molecules was carried out. As a result, stable dominant conformation was obtained and studied by quantum chemistry calculation. It was found that the four isoflavones indicated an association between free radical scavenging ability and electron transfer at the phenolic hydroxyl position as well as dehydrogenation capacity. Frontier molecular orbital could intuitively show the active sites of the molecules and based on energy gap and the enthalpy of formation of free radicals the antioxidant activity of the four isoflavones could be accurately ranked. Based on the enthalpy of formation of polyhydroxyl free radicals, 4＇-OH was the main hydroxyl active site of genistein and daidzein, and 3＇-OH was the main hydroxyl active site of pomiferin and osajin. Therefore, 4＇-OH and 3＇-OH can be considered as the representative active sites of the four isoflavonemolecules for scavenging free radicals.