College of Bee Science, Fujian Agriculture and Forestry University, Fuzhou 350002, PR China.
Key Laboratory of Bioorganic Phosphorous Chemistry and Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University, Beijing 100084, PR China.
Phytochemistry. 2019 Apr;160:19-24. doi: 10.1016/j.phytochem.2019.01.011. Epub 2019 Jan 19.
Flavonoids widely found in natural foods are characterized by acting as antioxidants compounds. There are close relationship between the antiradical activities and structural properties of flavonoids. In this work, density functional theory (DFT) methods were applied to investigate the influence of the H5⋯OC4 intramolecular hydrogen-bond (IHB) on the antiradical activity of flavonoid based on three prevalently accepted radical scavenging mechanisms: hydrogen atom transfer (HAT), single electron transfer-proton transfer (SET-PT) and sequential proton-loss electron-transfer (SPLET). The thermodynamic properties: bond dissociation enthalpy (BDE), ionization potential (IP), proton dissociation enthalpy (PDE), proton affinity (PA) and electron transfer enthalpy (ETE) related with these mechanisms were calculated to elucidate the antiradical activity. The results showed that the 5-OH group is most influenced and its antiradical capacity was weakened by the H5⋯OC4 IHB. In the gas, benzene and chloroform phases, H5⋯OC4 IHB would reduce the antiradical activity of flavonoid via increasing the bond dissociation enthalpy. While, in the DMSO and HO phases, the opposite result occurs by lowering the proton affinity.
黄酮类化合物广泛存在于天然食品中，其特点是作为抗氧化化合物发挥作用。黄酮类化合物的自由基清除活性与其结构特性密切相关。在这项工作中，应用密度泛函理论（DFT）方法研究了 H5⋯OC4 分子内氢键（IHB）对黄酮类化合物自由基清除活性的影响，基于三种普遍接受的自由基清除机制：氢原子转移（HAT）、单电子转移-质子转移（SET-PT）和顺序质子损失电子转移（SPLET）。计算了与这些机制相关的热力学性质：键离解焓（BDE）、电离势（IP）、质子离解焓（PDE）、质子亲合势（PA）和电子转移焓（ETE），以阐明其自由基清除活性。结果表明，H5⋯OC4 IHB 对 5-OH 基团的影响最大，其自由基清除能力减弱。在气相、苯相和氯仿相中，H5⋯OC4 IHB 通过增加键离解焓降低黄酮类化合物的自由基清除活性。然而，在 DMSO 和 HO 相中，通过降低质子亲合势则会产生相反的结果。
