Quenching of Triplet-Excited Flavins by Flavonoids. Structural Assessment of Antioxidative Activity
作者:Kevin Huvaere、Karsten Olsen、Leif H. Skibsted
DOI:10.1021/jo901301c
日期:2009.10.2
mechanism of flavin-mediated photooxidation of flavonoids was investigated for aqueous solutions. Interaction of triplet-excited flavin mononucleotide with phenols, as determined by laser flash photolysis, occurred at nearly diffusion-controlled rates (k ∼ 1.6 × 109 L mol−1 s−1 for phenol at pH 7, 293 K), but protection of the phenolic function by methylation inhibited reaction. Still, electron transfer was
研究了黄酮介导的类黄酮对水溶液的光氧化机理。与酚三重激发黄素单核苷酸的相互作用,如通过激光闪光光解来确定,发生在近扩散控制的速率(ķ〜1.6×10 9大号摩尔-1小号-1苯酚在pH为7,293 K),但保护通过甲基化抑制反应的酚功能。仍然,由于缺乏主要的动力学氢/氘同位素效应和低的光催化活化焓(<20 kJ mol -1),电子转移被认为是主导机制。活化熵起到补偿一系列酚类衍生物的作用,从而支持一种常见的氧化机理。一个邻-hydroxymethoxy图案也同样反应性的(ķ〜2.3×10 9大号摩尔-1小号-1在pH 7愈创木酚),其与化合物的邻-二羟基取代(ķ〜2.4×10 9大号摩尔-1小号-1pH为7的邻苯二酚时,通常称为良好的抗氧化剂。这驳斥了普遍的信念,即通过分子内氢键来稳定初始苯氧基自由基是降低邻苯二酚样化合物活性的驱动力。而是,这种键合改善了基底的电离特性,因此改善了与分离的酚