Nenadis Nikolaos, Siskos Dimitrios
Laboratory of Food Chemistry & Technology, School of Chemistry, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece.
Laboratory of Food Chemistry & Technology, School of Chemistry, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece.
Food Res Int. 2015 Oct;76(Pt 3):506-510. doi: 10.1016/j.foodres.2015.06.040. Epub 2015 Jul 8.
Hydroxytyrosol (HT) and a set of synthetic isochroman derivatives of HT have been studied with regards to their radical scavenging activity in the gas employing density functional theory (DFT) and the Becke's 3 Lee Yang Parr (B3LYP) functional. Values of molecular descriptors (bond dissociation enthalpy, BDE; ionization potential, IP; proton dissociation enthalpy, PDE; proton affinity, PA; electron transfer energy, ETE; electron accepting power, ɷ+; electron donating power, ɷ-; net electrophilicity, Δɷ) characterizing the hydrogen atom or electron donating efficiency of test compounds were used. Published experimental findings for the radical scavenging activity of the same compounds using methods such as Rancimat, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) radical cation and oxygen radical absorbance capacity were discussed. All the synthetic isochromans were predicted to be more potent hydrogen atom and electron donors than HT, though polarity may affect their performance in lipidic systems. Present findings point out that HT and examined isochromans prefer to scavenge free radicals via hydrogen atom transfer instead of electron donation and that allylic hydrogen atoms are expected to account for a higher activity in comparison to other phenolic antioxidants. The most potent hydrogen atom donor was the one bearing two catechol groups which can form stepwise a di-quinone and then scavenge additional radicals via allylic hydrogen atom donation and subsequent adduct formation. The total enthalpy required for all hydrogen atoms donated by test compounds was the most appropriate index of experimental activity prediction instead of common descriptors.
利用密度泛函理论（DFT）和贝克3李杨帕尔（B3LYP）泛函，对羟基酪醇（HT）及其一组合成异苯并二氢吡喃衍生物在气相中的自由基清除活性进行了研究。使用了表征测试化合物氢原子或电子供体效率的分子描述符值（键解离焓，BDE；电离势，IP；质子解离焓，PDE；质子亲和势，PA；电子转移能，ETE；电子接受能力，ɷ+；电子供体能力，ɷ-；净亲电性，Δɷ）。讨论了使用Rancimat、2,2'-偶氮双（3-乙基苯并噻唑啉-6-磺酸）自由基阳离子和氧自由基吸收能力等方法对相同化合物自由基清除活性的已发表实验结果。尽管极性可能会影响它们在脂质体系中的性能，但所有合成异苯并二氢吡喃预计都是比HT更强的氢原子和电子供体。目前的研究结果指出，HT和所研究的异苯并二氢吡喃更倾向于通过氢原子转移而非电子供体来清除自由基，并且与其他酚类抗氧化剂相比，烯丙基氢原子预计具有更高的活性。最有效的氢原子供体是带有两个儿茶酚基团的化合物，它可以逐步形成双醌，然后通过烯丙基氢原子供体和随后的加合物形成来清除额外的自由基。测试化合物捐赠所有氢原子所需的总焓是预测实验活性的最合适指标，而不是常用的描述符。
