大黄素和大黄素甲醚抗氧化活性的密度泛函理论研究

摘要

本文采用密度泛函理论(DFT)方法,在B3LYP/6-311G(d,p)水平下对气相和溶剂中大黄素和大黄素甲醚及其可能解离途径中形成的自由基进行结构优化,在结构优化的基础上用B3LYP/6-311++G(2 d,2 p)基组计算了其相应的单点能,通过三种抗氧化反应机制、清除·OOH自由基的机理等方面分析了分子活性位与其性质的关系,分析了两种物质酚羟基在不同环境中抗氧化活性的能力大小.计算结果表明,大黄素和大黄素甲醚分子分别在C3和C8位上酚羟基活性最高,是最大可能的活性位点,大黄素的酚羟基活性略高于大黄素甲醚.在气相中氢原子转移是主要的机制,在极性溶剂中单电子转移是主要机制,在非极性溶剂中连续的质子损失电子转移是主要机制.%In this paper,the structure of emodin,physcion and their free radicals in the formation of dissociation pathways were optimized using density functional theory (DFT) method with the B3LYP/6-311G(d,p) basis set level in gas phase and solvents.Then with B3LYP/6-311++G(2d,2p) basis set level the corresponding single point energy were calculated.The activity of the phenolic hydroxyls on different sites of emodin and physcion was discussed on the basis of the structure parameters,the frontier molecular orbitals and three antioxidant reaction mechanisms.The results show that 3-OH and 8-OH are the most activist site,respectively.Emodin's antioxidant activity is higher than physcion.The results obtained also demonstrate that HAT would be the most favourable mechanism in the gas phase,whereas the SPLET mechanism is the thermodynamically preferred pathway in polar media,and SET-PT is the main mechanism in nonpolar media.