Cotelle Nicole, Hapiot Philippe, Pinson Jean, Rolando Christian, Vézin Hervé
Laboratoire de Chimie Organique et Macromoléculaire, UMR CNRS-Université des Sciences et Technologies de Lille, N 8009, F-59655 Villeneuve d'Ascq Cedex, France.
J Phys Chem B. 2005 Dec 15;109(49):23720-9. doi: 10.1021/jp0550661.
The redox properties of a series of hydroxychalcones (a group of polyphenols abundantly present in plants) were investigated by cyclic voltammetry. As for many polyphenols, their beneficial properties have been mainly related to their antioxidant activities, which in turn are directly associated to their redox behavior. Two types of radicals can be produced that are localized on either one of the two aromatic systems. Their thermodynamic and kinetic parameters were extracted and compared to the predictions of density functional theory calculations. When at least one OH is present on each ring, their behaviors are dominated by the conjugated system: phenolic ring A-double bond-ketone, which is the only one to be oxidized. However, the redox properties of this conjugated system are strongly influenced by the presence of ring B. When an OH is present on ring B, an important feature is the existence of strong hydrogen bonding that remains almost unmodified even when ring A is oxidized. It does not considerably change the thermodynamics of ring A but strongly increases the rigidity of the molecule that remains planar under the neutral, anionic, or radical forms. Oxidation potentials of the phenolates range between 0.1 and 0.2 V versus a saturated calomel electrode, which correspond to species that are very easy to oxidize and lead to the rapid formation of nonradical species, underlining the potential antioxidant properties of these molecules.
通过循环伏安法研究了一系列羟基查尔酮（植物中大量存在的一类多酚）的氧化还原性质。与许多多酚一样，它们的有益特性主要与其抗氧化活性有关，而抗氧化活性又直接与其氧化还原行为相关。可以产生两种类型的自由基，它们定位于两个芳香体系中的任意一个上。提取了它们的热力学和动力学参数，并与密度泛函理论计算的预测结果进行了比较。当每个环上至少存在一个OH时，它们的行为由共轭体系主导：酚环A-双键-酮，这是唯一被氧化的部分。然而，该共轭体系的氧化还原性质受到环B存在的强烈影响。当环B上存在一个OH时，一个重要特征是存在强氢键，即使环A被氧化，该氢键也几乎保持不变。它不会显著改变环A的热力学，但会强烈增加分子的刚性，分子在中性、阴离子或自由基形式下均保持平面结构。相对于饱和甘汞电极，酚盐的氧化电位在0.1至0.2 V之间，这对应于非常容易氧化并导致快速形成非自由基物种的物质，突出了这些分子潜在的抗氧化特性。
