Flavonoids are known for their antiradical capacity, and this ability is strongly structure-dependent. In this research, the activity of flavones and flavonols in a water solvent was studied with the density functional theory methods. These included examination of flavonoids’ molecular and radical structures with natural bonding orbitals analysis, spin density analysis and frontier molecular orbitals theory. Calculations of determinants were performed: specific, for the three possible mechanisms of action—hydrogen atom transfer (HAT), electron transfer–proton transfer (ETPT) and sequential proton loss electron transfer (SPLET); and the unspecific—reorganization enthalpy (RE) and hydrogen abstraction enthalpy (HAE). Intramolecular hydrogen bonding, catechol moiety activity and the probability of electron density swap between rings were all established. Hydrogen bonding seems to be much more important than the conjugation effect, because some structures tends to form more intramolecular hydrogen bonds instead of being completely planar. The very first hydrogen abstraction mechanism in a water solvent is SPLET, and the most privileged abstraction site, indicated by HAE, can be associated with the C3 hydroxyl group of flavonols and C4’ hydroxyl group of flavones. For the catechol moiety, an intramolecular reorganization to an o-benzoquinone-like structure occurs, and the ETPT is favored as the second abstraction mechanism.

中文翻译：

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黄酮和黄酮的反自由基结构-活性关系-量子化学研究。

类黄酮以其抗自由基能力而闻名，这种能力强烈依赖于结构。在这项研究中，使用密度泛函理论方法研究了黄酮和黄酮醇在水溶剂中的活性。其中包括利用天然键合轨道分析，自旋密度分析和前沿分子轨道理论检查类黄酮的分子和自由基结构。进行了行列式的计算：具体来说，针对三种可能的作用机理-氢原子转移（HAT），电子转移-质子转移（ETPT）和顺序质子损失电子转移（SPLET）；以及非特异性的重组焓（RE）和氢提取焓（HAE）。分子内氢键 儿茶酚部分的活性和环之间电子密度交换的可能性都建立了。氢键似乎比共轭效应更为重要，因为某些结构倾向于形成更多的分子内氢键，而不是完全平面的。水溶剂中第一个氢提取机理是SPLET，HAE表示最优先的提取位点可与黄酮醇的C3​​羟基和黄酮的C4'羟基相关。对于儿茶酚部分，发生分子内重组为邻苯醌样结构，并且ETPT被优选为第二抽象机制。因为一些结构倾向于形成更多的分子内氢键，而不是完全平面的。水溶剂中第一个氢提取机理是SPLET，HAE表示最优先的提取位点可与黄酮醇的C3​​羟基和黄酮的C4'羟基相关。对于邻苯二酚部分，发生分子内重组为邻苯醌样结构，并且ETPT被认为是第二种抽象机理。因为一些结构倾向于形成更多的分子内氢键，而不是完全平面的。水溶剂中最早的氢提取机理是SPLET，HAE表示最优先的提取位点可与黄酮醇的C3​​羟基和黄酮的C4'羟基相关。对于儿茶酚部分，发生分子内重组为邻苯醌样结构，并且ETPT被优选为第二抽象机制。