黄芩素和黄芩苷抗氧化活性与结构关系的密度泛函理论研究

The density functional theory studies on the relationship between antioxidant activity and structure of Baicalein and Baicalin

采用密度泛函理论方法对黄芩素和黄芩苷分子进行构象扫描,获得2个化合物的最低能量构象并对其进行了全优化.从分子的几何结构、酚羟基解离能BDE、绝热电离势IP、HOMO和LUMO能级以及其能级差ΔE(LUMO-HOMO)等方面分析了2个化合物的抗氧化活性与结构的关系.结果表明,C6位的酚羟基为黄芩素和黄芩苷的最大反应活性位点.在非极性溶剂中,化合物抗氧化活性取决于分子中酚羟基的脱氢能力,黄芩苷的抗氧化活性大于黄芩素的抗氧化活性.在极性溶剂中,抗氧化活性取决于分子中单电子的电离势,黄芩苷的抗氧化活性大于黄芩素的抗氧化活性.

The conformation of baicalein and baicalin were investigated by the Density Functional Theory method to search the minimum energy conformers. The properties of the stable conformers have been discussed in detail based on the molecular geometries,the bond dissociation enthalpies(BDE) and hydroxyl ionization potential(IP),the energies of the highest occupied molecular orbital(HOMO) and the lowest unoccupied molecular orbital(LUMO),the energy gap between HOMO and LUMO. It was found that the lower bond dissociation enthalpies(BDE) and ionization potential(IP) of the hydroxyl,the higher energy level of the HOMO and the smaller ΔE(LUMO-HOMO)were benefit to the antioxidant activity of baicalein and baicalin. The results showed that antioxidant properties of baicalein and baicalin derived from dehydrogenation capacity of hydroxyl group and the electron abstraction,the C6-OH was the highest active site of baicalein and baicalin. In non-polar solvents,the antioxidant activity of baicalin was higher than that of baicalein. However,in polar solvents,the antioxidant activity of baicalin was higher than that of baicalein.