基于DFT方法研究甘草中黄酮类化合物的抗氧化活性

Investigation on Antioxidant Activity of Flavonoids From Licorice Based on Density Functional Theory

基于密度泛函(DFT)方法研究甘草中黄酮类化合物的抗氧化活性,对甘草素、甘草苷、异甘草素和异甘草苷4种化合物的分子结构及其相应的自由基进行了理论计算。分别在气相和溶剂中获得了4种化合物及其相应自由基的最优几何结构、NBO电荷、BDE和IP等量子化学参数。计算结果显示:4种化合物的抗氧化活性由大到小的顺序为异甘草素、异甘草苷、甘草素、甘草苷,与实验活性顺序一致,并且4种化合物中C7位是自由基反应的最大可能活性位点。

In order to study the relationship between the structure and antioxidant activity of flavonoids from licorice,the density functional theory(DFT)B3 LYP method with 6-31+G**basis sets was used to optimize the structures of liquiritigenin,liquiritin,isoliquiritigenin,isoliquiritoside and the corresponding free radicals.The properties of the stable geometries were discussed on basis of the molecular geometries,the natural bond order(NBO)charges,the bond dissociation enthalpies(BDE),ionization potential(IP)and the frontier molecular orbitals theory.The results revealed that the sequence of antioxidant activity of these four flavonoid compounds was:isoliquiritigenin>isoliquiritoside>liquiritigenin>liquiritin,which was consistent with the experimental conclusions.The calculated BDE values for flavonoid compounds clearly demonstrated that the site of C7—OH was the most active site.