Shanxi Center for Testing of Functional Agro-Products, Shanxi Agricultural University, Taiyuan 030031, China.
Molecules. 2023 Jun 28;28(13):5039. doi: 10.3390/molecules28135039.
As a valuable traditional Chinese herbal medicine, Radix Astragali has attracted much attention due to its extensive pharmacological activities. In this study, density functional theory (DFT) was used thermodynamically and kinetically in detail to predict the antioxidant activity and reaction mechanisms involved in the free radical scavenging reactions of three representative isoflavonoids (formononetin, calycosin, and calycosin-7-glucoside) extracted from Radix Astragali. Three main mechanisms, including hydrogen atom transfer (HAT), proton transfer after electron transfer (SET-PT), and sequential proton loss electron transfer (SPLET) were examined by calculating the thermodynamic parameters. It was found that HAT is the predominant mechanism in the gas phase, while SPLET is supported in the solvent environment. The isoflavonoids' order of antioxidant activity was estimated as: calycosin > calycosin-7-glucoside > formononetin. For the calycosin compound, the result revealed the feasibility of double HAT mechanisms, which involve the formation of stable benzodioxazole with significantly reduced energy in the second H/e reaction. In addition, the potential energy profiles and kinetic calculations show that the reaction of OH into the 3'-OH site of calycosin has a lower energy barrier (7.2 kcal/mol) and higher rate constant (4.55 × 10 M s) compared with other reactions in the gas phase.
作为一种有价值的中草药，黄芪因其广泛的药理活性而备受关注。在这项研究中，我们使用密度泛函理论（DFT）从热力学和动力学两个方面详细预测了从黄芪中提取的三种代表性异黄酮（芒柄花素、毛蕊异黄酮和毛蕊异黄酮-7-O-葡萄糖苷）清除自由基反应的抗氧化活性和反应机制。通过计算热力学参数，考察了三种主要机制，包括氢原子转移（HAT）、电子转移后质子转移（SET-PT）和顺序质子丢失电子转移（SPLET）。结果表明，在气相中，HAT 是主要机制，而在溶剂环境中支持 SPLET。异黄酮抗氧化活性的顺序估计为：毛蕊异黄酮>毛蕊异黄酮-7-O-葡萄糖苷>芒柄花素。对于毛蕊异黄酮化合物，结果表明双 HAT 机制的可行性，该机制涉及到在第二个 H/e 反应中形成稳定的苯并二恶唑，能量显著降低。此外，势能曲线和动力学计算表明，在气相中，OH 与毛蕊异黄酮 3'-OH 位点的反应具有较低的能量势垒（7.2 kcal/mol）和较高的速率常数（4.55×10 M s）。
