Kinetic and Thermochemical Study of the Antioxidant Activity of Sulfur-Containing Analogues of Vitamin E
作者:Riccardo Amorati、Andrea Cavalli、Maria Grazia Fumo、Matteo Masetti、Stefano Menichetti、Chiara Pagliuca、Gian Franco Pedulli、Caterina Viglianisi
DOI:10.1002/chem.200700309
日期:2007.10.5
into the framework of vitamin E. This behavior implies a greater deviation of the condensed ring from coplanarity with the aromatic ring, thus giving rise to a decrease in the conjugative stabilization of the phenoxyl radical and consequently to an increase in the O--H bond strength. Although less reactive than tocopherols, thiachromanols may, however, act as bimodal antioxidants as a result of the hydroperoxide
合成或连接或不连接邻苯二酚部分的维生素E的含硫类似物(硫代铬烷醇),并评估其氢原子给体能力。通过电子顺磁共振(EPR)平衡技术测定α-生育酚类似物4的O-H键解离焓(BDE)提供了78.9 kcal mol(-1)的值,即大约1.8 kcal mol (-1)高于α-生育酚。通过抑制的自氧化研究测得的与过氧自由基的反应动力学速率常数(kinh)表明,硫代苯并色酚的反应速度比相应的生育酚慢2.5倍,这与较高的BDE值相符。在晶体学分析和DFT计算的基础上,对这种行为进行了解释,就由于将硫原子插入维生素E的骨架而引起的分子几何形状的变化而言。这种行为暗示了稠环与芳环的共面性更大的偏离,从而导致了共轭稳定性的降低。苯氧基自由基的生成,从而提高了O-H键的强度。尽管硫酚的反应活性不如生育酚,但由于硫原子的氢过氧化物分解能力,它们可能充当双峰型抗氧化剂。