Institute of Research and Development, Duy Tan University , 03 Quang Trung, Danang 550000, Viet Nam.
Campus in Kon Tum, The University of Danang , 704 Phan Dinh Phung, Kon Tum 580000, Viet Nam.
J Phys Chem B. 2017 Oct 12;121(40):9348-9357. doi: 10.1021/acs.jpcb.7b07065. Epub 2017 Sep 28.
Antioxidant efficiency of all-trans-retinol has been studied on the basis of characteristic thermochemical properties using density functional theory. The influence of the solvent polarity has also been evaluated. It is found that retinol may act in parallel as an effective antioxidant via H atom donating as well as a pro-oxidant in yielding reactive hydroxyl radical. In fact, the lowest values of bond dissociation enthalpy were found at the C18-H and C18-OH positions. Retinol was also determined to be a good electron donor but bad acceptor in the single electron transfer (ET) reaction with hydroperoxyl (HOO) radical. In addition, potential energy surfaces of H atom transfer (HAT) and radical adduct formation (RAF) reactions between retinol and HOO radical were also investigated in the gas phase and in the solvent. The results demonstrated that the RAF mechanism was generally more predominant than ET and HAT ones. The most favored radical addition position was found at the C2═C3 double bond in the cyclohexenyl ring. Moreover, the radical scavenging reactivity via RAF reactions was strongly exergonic and thermodynamically feasible while the ET one was endergonic. Natural bond orbital analysis showed that the lone pairs of electrons on the oxygen atom of the HOO radical were donated to the unoccupied antibonding orbital of transferred H atom in HAT reactions. In contrast, in the case of RAF reactions, strong interactions between 2p orbitals on oxygen atoms of the radical and the π orbital of the double bond on the retinol molecule were recognized. The results obtained in this work were in agreement with previous experimental observations.
基于特征热化学性质，使用密度泛函理论研究了全反式视黄醇的抗氧化效率，并评估了溶剂极性的影响。研究发现，视黄醇可能通过 H 原子供体和产生反应性羟基自由基的促氧化剂，同时作为有效的抗氧化剂发挥作用。事实上，在 C18-H 和 C18-OH 位置发现了最低的键离解焓值。在与过氧自由基 (HOO) 的单电子转移 (ET) 反应中，视黄醇也被确定为良好的电子供体，但不是良好的电子受体。此外，还在气相和溶剂中研究了视黄醇与 HOO 自由基之间的 H 原子转移 (HAT) 和自由基加成物形成 (RAF) 反应的势能面。结果表明，RAF 机制通常比 ET 和 HAT 机制更为优势。在环己烯环中的 C2═C3 双键处发现了最有利于加成的自由基位置。此外，通过 RAF 反应的自由基清除反应是强烈的放热和热力学可行的，而 ET 反应是吸热的。自然键轨道分析表明，HOO 自由基氧原子上的孤对电子被转移 H 原子的未占据反键轨道捐赠给 HAT 反应。相比之下，在 RAF 反应中，自由基氧原子上的 2p 轨道和视黄醇分子上的双键的π轨道之间存在强烈的相互作用。本工作的结果与先前的实验观察结果一致。
