Đorović Jelena, Marković Jasmina M Dimitrić, Stepanić Višnja, Begović Nebojša, Amić Dragan, Marković Zoran
Bioengineering Research and Development Center, 34000, Kragujevac, Republic of Serbia,
J Mol Model. 2014 Jul;20(7):2345. doi: 10.1007/s00894-014-2345-y. Epub 2014 Jun 26.
The M05-2X/6-311++G(d,p) and B3LYP-D2/6-311++G(d,p) models are used to evaluate scavenging potency of gallic acid. The hydrogen atom transfer (HAT), sequential proton loss electron transfer (SPLET), and single electron transfer followed by proton transfer (SET-PT) mechanisms of gallic acid with some radicals ((•)OO(-), (•)OH, and CH3OO(•)) were investigated using the corresponding thermodynamic quantities: bond dissociation enthalpy (BDE), ionization potential (IP), and proton affinity (PA). Namely, the ΔHBDE, ΔHIP, and ΔHPA values of the corresponding reactions in some solvents (water, DMSO, pentylethanoate, and benzene) are investigated using an implicit solvation model (SMD). An approach based on the reactions enthalpies related to the examined mechanisms is applied. This approach shows that a thermodynamically favored mechanism depends on the polarity of reaction media and properties of free radical reactive species. The most acidic 4-OH group of gallic acid is the active site for radical inactivation. The results of this investigation indicate that the SPLET mechanism can be a favored reaction pathway for all three radicals in all solvents, except for (•)OH in the aqueous solution. In water, gallic acid can inactivate (•)OH by the HAT mechanism.
采用M05 - 2X/6 - 311++G(d,p)和B3LYP - D2/6 - 311++G(d,p)模型评估没食子酸的清除能力。利用相应的热力学量：键解离焓（BDE）、电离势（IP）和质子亲和能（PA），研究了没食子酸与一些自由基（(•)OO(-)、(•)OH和CH3OO(•)）的氢原子转移（HAT）、连续质子损失电子转移（SPLET）以及单电子转移后质子转移（SET - PT）机制。具体而言，使用隐式溶剂化模型（SMD）研究了在一些溶剂（水、二甲基亚砜、戊酸乙酯和苯）中相应反应的ΔHBDE、ΔHIP和ΔHPA值。应用了一种基于与所研究机制相关的反应焓的方法。该方法表明，热力学上有利的机制取决于反应介质的极性和自由基活性物种的性质。没食子酸中酸性最强的4 - OH基团是自由基失活的活性位点。该研究结果表明，除了在水溶液中与(•)OH反应外，SPLET机制可能是在所有溶剂中与所有三种自由基反应的有利反应途径。在水中，没食子酸可以通过HAT机制使(•)OH失活。
