Holtomo Olivier, Nsangou Mama, Fifen Jean Jules, Motapon Ousmanou
Department of Physics, Faculty of Science, University of Bamenda, Bambili P. O. Box 39, Cameroon; Laboratory of Fundamental Physics, Faculty of Science,University of Douala, Douala P. O. Box 24157, Cameroon.
Department of Physics, Higher Teacher's Training College, University of Maroua, Maroua P. O. Box 46, Cameroon; Department of Physics, Faculty of Science, University of Ngaoundere, Ngaoundere P. O. Box 454, Cameroon.
J Mol Graph Model. 2017 Nov;78:221-233. doi: 10.1016/j.jmgm.2017.10.014. Epub 2017 Oct 28.
DFT methods including B3LYP, B3PW91 and M05-2x associated to 6-31+G(d,p) were used for the structural and antioxidant potency studies of phenylethyl-3,4-dihydroxy-hydrocinnamate (PDH). Solvents were employed according to their protric and aprotic character. So, calculated structures agree with the experimental data. OH is propitious to scavenge radicals whatever the medium except in water where OH and OH are competitive. The explicit solvents of dichloromethane (DCM) and water present a disparity of OH bond dissociation enthalpy and free energy (BDE and BDFE). These parameters are low in continuum except in water. The ionization potentials (IP) and potential affinities (PA) are low in solvents. BDE, IP and PA are each, approximatively constant in mixed solvent treatment in water using n-HO (n=3,5,8). Elsewhere, H-atom transfer (HAT) mechanism is favoured in vacuum and DCM, whereas sequential proton loss electron transfer (SPLET) is likely in protic solvents. A discord between HAT and SPLET in benzene is observed. The PDH compound is more antioxidant and resistant to oxidation than caffeic acid phenethyl ester (CAPE). The potential of scavenging of OH and OOH whatever the reaction channel shows that they decay rapidly in any media through HAT. PDH is easily deprotonated in the protic solvents and the resulting product is the most antioxidant and the least resistant to oxidation.
采用包括B3LYP、B3PW91和M05-2x并结合6-31+G(d,p)的密度泛函理论（DFT）方法，对3,4-二羟基苯丙酸苯乙酯（PDH）进行结构和抗氧化活性研究。根据溶剂的质子性和非质子性来选择使用的溶剂。因此，计算得到的结构与实验数据相符。无论在何种介质中，除了在水介质中OH和OH存在竞争关系外，OH有利于清除自由基。二氯甲烷（DCM）和水这两种显式溶剂在OH键解离焓和自由能（BDE和BDFE）方面存在差异。除了在水中，这些参数在连续介质中较低。在溶剂中，电离势（IP）和亲和势（PA）较低。在使用正丁醇（n = 3、5、8）的水混合溶剂处理中，BDE、IP和PA各自大致恒定。在其他地方，在真空和DCM中，氢原子转移（HAT）机制占优势，而在质子性溶剂中，顺序质子损失电子转移（SPLET）可能占优势。在苯中观察到HAT和SPLET之间存在不一致。PDH化合物比咖啡酸苯乙酯（CAPE）具有更强的抗氧化性和抗氧化能力。无论反应途径如何，PDH对OH和OOH的清除潜力表明它们在任何介质中都通过HAT迅速衰减。PDH在质子性溶剂中很容易去质子化，生成的产物具有最强的抗氧化性和最弱的抗氧化能力。
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