Departamento de Ensino, Instituto Federal de Educação Ciência e Tecnologia do Ceará, Quixadá, CE, CEP 63902-580, Brazil.
Departamento de Química Analítica e Físico‑Química, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, CE, CEP 60440‑900, Brazil.
J Mol Model. 2022 Apr 30;28(5):133. doi: 10.1007/s00894-022-05120-z.
This work investigated the antioxidant potential of acetylated and nitrated eugenol derivatives through structural analysis and the mechanism of hydrogen atomic transfer (HAT) by density functional theory (DFT). The structures were optimized by the hybrid functional M06-2X with basis set 6-31 + G(d,p), and the HAT mechanism was evaluated with HO, HOO, CHO, DPPH radicals. In agreement with experimental data from previous studies, two steps of hydrogen transfer were tested. The thermodynamic data showed the need for two hydrogen atomic transfer steps from antioxidants, followed by the formation of p-quinomethanes (27, 28, and 29) to make the reaction spontaneous with DPPH. Furthermore, theoretical kinetic data showed that the preferred antioxidant site depends on the instability of the attacking radical and confirmed the antioxidant profile for eugenol (1, 4-allylbenzene-1,2-diol), and nitro-derivative 7 (5-allyl-3-nitrobenzene-1,2-diol) in the DPPH assay. Finally, this study showed that nitro compound 6 (4-allyl-2-methoxy-6-nitrophenol) also has anti-radical activity with smaller radicals but is not observed in the experiment due to structural characteristics and chemoselectivity of DPPH.
这项工作通过密度泛函理论（DFT）的结构分析和氢原子转移（HAT）机制研究了乙酰化和硝化丁香酚衍生物的抗氧化潜力。采用混合泛函 M06-2X 和基组 6-31 + G(d,p)对结构进行了优化，并使用 HO、HOO、CHO、DPPH 自由基评估了 HAT 机制。与先前研究的实验数据一致，测试了两步氢转移。热力学数据表明，抗氧化剂需要经过两步氢原子转移，然后形成 p-醌甲烷（27、28 和 29），使反应与 DPPH 自发进行。此外，理论动力学数据表明，首选的抗氧化剂部位取决于攻击自由基的不稳定性，并证实了丁香酚（1,4-烯丙基苯-1,2-二醇）和硝基衍生物 7（5-烯丙基-3-硝基苯-1,2-二醇）在 DPPH 测定中的抗氧化特性。最后，这项研究表明，硝基化合物 6（4-烯丙基-2-甲氧基-6-硝基苯酚）也具有抗自由基活性，但其活性较小，但由于 DPPH 的结构特征和化学选择性，在实验中未观察到。
