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利用密度泛函理论的B3LYP交换相关泛函对从细梗胡枝子中提取的一种新型黄酮类化合物的分子结构和抗氧化活性进行了研究,获得了该化合物的中性分子、阴离子、自由基和自由基阳离子的稳定几何构型和能量.通过分析前线分子轨道特征,确定了与实验结果一致的现象:A环是参加化学反应的活性部位,并发现A′环也是重要的抗氧化活性部位.为判断其抗氧化活性,预测其水溶液中,中性和阴离子的电离势分别为509.0和432.2kJ.mol-1,均裂O—H键解离能为347.3kJ.mol-1,羟基自由基电子亲和势和氢原子亲和势分别为-620.6和-487.5kJ.mol-1.通过理论分析比较,该黄酮类化合物清除羟基自由基的三种机理即H原子转移、电子转移-质子转移和质子丢失-电子转移在热力学上并存,其中质子丢失-电子转移是热力学最有利的机理.本文为设计新型高效黄酮类抗氧化剂,研究黄酮类化合物的构效关系和抗氧化机理提供了理论依据.
The molecular structure and antioxidative activity of a novel flavonoid extracted from the Lespedeza macrostachya rhizome were studied using density functional theory (B3LYP) exchange correlation function, and the neutral molecules, anions, free radicals And the stable geometry and energy of the radical cation.The phenomenon consistent with the experimental results was confirmed by analyzing the frontier molecular orbital characteristics: the A ring is the active site participating in the chemical reaction and the A ’ring is also found to be an important antioxidant activity site In order to determine its antioxidant activity, the ionization potentials of the neutral and anionic ions in aqueous solution were predicted to be 509.0 and 432.2 kJ · mol-1, respectively, and the cleaved O-H bond cleavage energy was 347.3 kJ · mol-1. The electron affinity and hydrogen affinity were-620.6 and -487.5kJ · mol-1, respectively. By theoretical analysis and comparison, the three mechanisms of hydroxyl radical scavenging by this flavonoid were H atom transfer, electron transfer-proton Metastasis and proton loss - Electron transfer co-exists in thermodynamics, of which proton loss - electron transfer is the thermodynamics of the most favorable mechanism.In this paper, a new type of high-performance flavonoids antioxidants, the structure of flavonoids research Relationship and antioxidant mechanism provides a theoretical basis.