Gregor Wolfgang, Grabner Gottfried, Adelwöhrer Christian, Rosenau Thomas, Gille Lars
Research Institute for Pharmacology and Toxicology of Oxygen Radicals, University of Veterinary Medicine Vienna, Vienna, Austria.
J Org Chem. 2005 Apr 29;70(9):3472-83. doi: 10.1021/jo047927s.
[structure: see text] Chromanol-type compounds act as antioxidants in biological systems by reduction of oxygen-centered radicals. Their efficiency is determined by the reaction rate constants for the primary antioxidative reaction as well as for disproportionation and recycling reactions of the antioxidant-derived radicals. We studied the reaction kinetics of three novel chromanols: cis- and trans-oxachromanol and the dimeric twin-chromanol, as well as ubichromanol and ubichromenol, in comparison to alpha-tocopherol and pentamethylchromanol. The antioxidant-derived radicals were identified by optical and electron spin resonance spectroscopy (ESR). The kinetics of the primary antioxidative reaction and the disproportionation of the chromanoxyl radicals were assessed by stopped-flow photometry in different organic solvents to simulate the different polarities associated with biomembranes. Furthermore, the reduction of the chromanoxyl radicals by ubiquinol and ascorbate was measured after laser-induced one-electron chromanol oxidation in ethanol and in a micellar system, respectively. The rate constants showed that twin-chromanol had better radical scavenging properties than alpha-tocopherol and a significantly slower disproportionation rate of its corresponding chromanoxyl radical. In addition, the radical derived from twin-chromanol is reduced by ubiquinol and ascorbate at a faster rate than the tocopheroxyl radical. Finally, twin-chromanol can deliver twice as many reducing equivalents, which makes this compound a promising new candidate as artificial antioxidant in biological systems.
[结构：见正文] 色满醇类化合物在生物系统中通过还原以氧为中心的自由基而起到抗氧化剂的作用。它们的效率由初级抗氧化反应以及抗氧化剂衍生自由基的歧化和循环反应的反应速率常数决定。我们研究了三种新型色满醇（顺式和反式氧杂色满醇以及二聚体双色满醇）以及泛色满醇和泛色满烯醇与α-生育酚和五甲基色满醇相比的反应动力学。通过光学和电子自旋共振光谱（ESR）鉴定了抗氧化剂衍生的自由基。在不同的有机溶剂中通过停流光度法评估初级抗氧化反应的动力学以及色满氧基自由基的歧化，以模拟与生物膜相关的不同极性。此外，分别在乙醇和胶束体系中激光诱导单电子色满醇氧化后，测量了泛醌醇和抗坏血酸对色满氧基自由基的还原作用。速率常数表明，双色满醇比α-生育酚具有更好的自由基清除性能，并且其相应色满氧基自由基的歧化速率明显更慢。此外，泛醌醇和抗坏血酸还原双色满醇衍生的自由基的速率比生育酚氧基自由基更快。最后，双色满醇可以提供两倍数量的还原当量，这使得该化合物成为生物系统中一种有前途的新型人工抗氧化剂候选物。
