杨梅酮的抗氧化活性

采用密度泛函理论(DFT)方法, 研究了杨梅酮的分子结构、电子结构和羟基离解焓, 并探讨了杨梅酮与OOCH₃·自由基发生反应的抗氧化机理. 自由基发生反应的抗氧化机理. 在M06-2X/6-31++G(d,p)的计算水平下, 得到了杨梅酮脱氢后各种自由基的相对能量、羟基离解焓、氢原子提取的活化能垒和速率常数. 计算结果表明杨梅酮的4'-OH位置具有最高的抗氧化活性. 杨梅酮4'-OH位置的高活性, 主要是由于4'位上脱氢后生成的羰基与相邻的羟基之间形成了稳定的氢键. 分子中的原子(AIM)理论分析表明, 这种氢键相互作用能够稳定氢提取过程中产生的自由基. 对杨梅酮抗氧化性机理的理论研究, 可为今后设计合成新型的具有更强活性的抗氧化物提供坚实的理论基础.

Radical Scavenging Activity of Myricetin

Density functional theory (DFT) calculations have been performed to explore the molecular structure, electronic structure, and O－H bond dissociation enthalpy of myricetin. Possible antioxidation mechanisms between lipid peroxide radical CH₃OO· and myricetin have been discussed. DFT calculations at the M06-2X/6-31++G(d,p) level indicated that the 4'-OH group of myricetin is the most active site on the basis of the stability of dehydrogenated myricetin radicals, O－H bond dissociation enthalpy, and hydrogen abstraction activation barrier, as well as kinetic data for myricetin determined at different temperatures. The relatively high activity of the 4'-OH site can be ascribed to weak hydrogen-bonding interactions between the oxygen radical of the reactive OH group and the adjacent OH group in the B-ring, which is retained upon going from free myricetin to reactant complex to product according to atoms in molecule (AIM) analysis. The hydrogen-bond helps to stabilize the electronic deficiency generated on the oxygen radical during the hydrogen abstraction reaction. All calculations are in agreement with the structure-activity relationship previously established for myricetin by considering its antioxidant activity. Present calculations provide theoretical basis for the designing new antioxidants.