Scavenging Mechanism of Curcumin Toward the Hydroxyl Radical: A Theoretical Study of Reactions Producing Ferulic Acid and Vanillin
Scavenging Mechanism of Curcumin Toward the Hydroxyl Radical: A Theoretical Study of Reactions Producing Ferulic Acid and Vanillin
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DOI：
10.1021/jp209318f
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发表时间：
2011-12-15
影响因子：
2.9
通讯作者：
Mishra, P. C.
中科院分区：
文献类型：
--
作者：
Agnihotri, Neha;Mishra, P. C.
姜黄素是一种抗氧化剂，因为它可以从生物介质中清除自由基。一个序列的H-提取和加成反应，涉及多达8个OH自由基和姜黄素或其降解产物，导致形成其他两种抗氧化剂，即阿魏酸和香草醛，进行了研究。姜黄素的单电子转移到OH自由基进行了研究。在密度泛函理论BHandHLYP/6- 31 G（d，p）水平上，通过优化反应物和产物配合物的几何构型以及过渡态的几何构型，确定了气相反应体系势能面上所有相关极值的位置.在BHandHLYP/aug-cc-pVDZ和B3 LYP/aug-cc-pVDZ水平上进行了气相单点能计算。水介质中的溶剂效应进行了处理，通过执行单点能量计算在所有上述水平的理论采用极化连续模型和几何优化在BHandHLYP/6- 31 G（d，p）水平在气相中。几个反应步骤也进行了研究，在水介质中的几何优化，由此获得的吉布斯自由能垒是类似的，通过相应的单点能量计算得到的。我们的计算表明，连接到姜黄素的苯酚部分的OH基团的氢原子将最有效地提取的OH自由基，与实验观察一致。此外，我们的研究表明，OH加成将是最有利的在C10网站的hepepropylene链。研究发现，姜黄素可以作为一种有效的抗氧化剂。
Curcumin is known to be an antioxidant, as it can scavenge free radicals from biological media. A sequence of H-abstraction and addition reactions involving up to eight OH radicals and curcumin or its degradation products leading to the formation of two other antioxidants, namely, ferulic acid and vanillin, was studied. Single electron transfer from curcumin to an OH radical was also studied. All relevant extrema on the potential energy surfaces were located by optimizing geometries of the reactant and product complexes, as well as those of the transition states, at the BHandHLYP/6-31G(d,p) level of density functional theory in the gas phase. Single-point energy calculations were also performed in the gas phase at the BHandHLYP/aug-cc-pVDZ and B3LYP/aug-cc-pVDZ levels of theory. Solvent effects in aqueous media were treated by performing single-point energy calculations at all of the above-mentioned levels of theory employing the polarizable continuum model and the geometries optimized at the BHandHLYP/6-31G(d,p) level in the gas phase. A few reaction steps were also studied by geometry optimization in aqueous media, and the thus-obtained Gibbs free energy barriers were similar to those obtained by corresponding single-point energy calculations. Our calculations show that the hydrogen atom of the OH group attached to the phenol moiety of curcumin would be most efficiently abstracted by an OH radical, in agreement with experimental observations. Further, our study shows that OH addition would be most favored at the C10 site of the heptadiene chain. It was found that curcumin can serve as an effective antioxidant.