Department of Chemical-Technological Sciences, State University of Novi Pazar, Vuka Karadžića bb, 36300 Novi Pazar, Serbia.
Food Chem. 2012 Dec 1;135(3):2070-7. doi: 10.1016/j.foodchem.2012.05.119. Epub 2012 Jun 9.
Due to intramolecular H-atom transfer, deprotonation of the most acidic 3-OH group of morin yields 2'-O(-) phenoxide anion. The reaction enthalpies related to mechanisms of free radical scavenging activity of this dominant species at a physiological pH of 7.4 were calculated by PM6 and DFT methods in gas-phase, water, benzene and DMSO. Results indicate the 4'-OH group of 2'-O(-) phenoxide anion is the active site for radical inactivation. The thermodynamically favoured mechanism depends on the polarity of the reaction media: in polar solvents (water and DMSO), the sequential proton loss electron transfer (SPLET) mechanism is preferred while in non-polar benzene (and in gas-phase), the hydrogen atom transfer (HAT) mechanism is responsible for the free radical scavenging activity of the morin phenoxide anion. Results show that the fast, semiempirical PM6 method fairly mimics more accurate, though time-consuming DFT methodologies.
由于分子内 H 原子转移，荭草素最酸性的 3-OH 基团脱质子生成 2'-O(-) 苯氧阴离子。通过 PM6 和 DFT 方法在气相、水、苯和 DMSO 中计算了该主要物种在生理 pH 值 7.4 下的自由基清除活性相关的反应焓。结果表明，2'-O(-) 苯氧阴离子的 4'-OH 基团是自由基失活的活性部位。热力学有利的机制取决于反应介质的极性：在极性溶剂（水和 DMSO）中，优先选择顺序质子损失电子转移（SPLET）机制，而在非极性苯（和气相中），氢原子转移（HAT）机制负责荭草素苯氧阴离子的自由基清除活性。结果表明，快速、半经验的 PM6 方法相当模拟了更准确、尽管耗时的 DFT 方法。
