Guo Q, Packer L
Department of Molecular and Cell Biology, University of California at Berkeley, 94720-3200, USA.
Free Radic Biol Med. 2000 Aug;29(3-4):368-74. doi: 10.1016/s0891-5849(00)00309-9.
In the redox antioxidant network, dihydrolipoate can synergistically enhance the ascorbate-dependent recycling of vitamin E. Since the major endogenous thiol antioxidant in biological systems is glutathione (GSH) it was of interest to compare the effects of dihydrolipoate with GSH on ascorbate-dependent recycling of the water-soluble homologue of vitamin E, Trolox, by electron spin resonance (ESR). Trolox phenoxyl radicals were generated by a horseradish peroxidase (HRP)-hydrogen peroxide (H2O2) oxidation system. In the presence of dihydrolipoate, Trolox radicals were suppressed until both dihydrolipoate and endogenous levels of ascorbate in skin homogenates were consumed. Similar experiments made in the presence of GSH revealed that Trolox radicals reappeared immediately after ascorbate was depleted and that GSH was not able to drive the ascorbate-dependent Trolox recycling reaction. However, at higher concentrations GSH was able to increase ascorbate-mediated Trolox regeneration from the Trolox radical. ESR and spectrophotometric measurements demonstrated the ability of dihydrolipoate or GSH to react with dehydroascorbate, the two-electron oxidation product of ascorbate in this system. Dihydrolipoate regenerated greater amounts of ascorbate at a much faster rate than equivalent concentrations of GSH. Thus the marked difference between the rate and efficiency of ascorbate generation by dihydrolipoate as compared with GSH appears to account for the different kinetics by which these thiol antioxidants influence ascorbate-dependent Trolox recycling.
在氧化还原抗氧化剂网络中，二氢硫辛酸可协同增强维生素E的抗坏血酸依赖性循环利用。由于生物系统中主要的内源性硫醇抗氧化剂是谷胱甘肽（GSH），因此通过电子自旋共振（ESR）比较二氢硫辛酸与GSH对维生素E的水溶性类似物Trolox的抗坏血酸依赖性循环利用的影响很有意义。Trolox苯氧自由基由辣根过氧化物酶（HRP）-过氧化氢（H2O2）氧化系统产生。在二氢硫辛酸存在的情况下，Trolox自由基受到抑制，直到皮肤匀浆中的二氢硫辛酸和内源性抗坏血酸水平都被消耗殆尽。在GSH存在下进行的类似实验表明，抗坏血酸耗尽后Trolox自由基立即重新出现，并且GSH无法驱动抗坏血酸依赖性的Trolox循环反应。然而，在较高浓度下，GSH能够增加抗坏血酸介导的Trolox自由基再生为Trolox。ESR和分光光度测量证明了二氢硫辛酸或GSH与脱氢抗坏血酸（该系统中抗坏血酸的双电子氧化产物）反应的能力。与同等浓度的GSH相比，二氢硫辛酸以更快的速度再生了更多的抗坏血酸。因此，与GSH相比，二氢硫辛酸生成抗坏血酸的速率和效率的显著差异似乎解释了这些硫醇抗氧化剂影响抗坏血酸依赖性Trolox循环利用的不同动力学。
