Generation of superoxide and singlet oxygen from alpha-tocopherolquinone and analogues.
Generation of superoxide and singlet oxygen from alpha-tocopherolquinone and analogues.
复制标题
α-生育酚和类似物的超氧化物和单线氧产生。
DOI：
10.1080/10715760701324075
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发表时间：
2007-06
影响因子：
3.3
通讯作者：
Bisby, Roger H
中科院分区：
文献类型：
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作者：
Crisostomo, Ana G;Moreno, Raphael B;Navaratnam, Suppiah;Wilkinson, James A;Bisby, Roger H
已经确定了从α-生育酚醌产生活性氧的三种潜在途径。水溶性维生素E类似物Trolox C（Trol-Q）的醌被水合电子和异丙醇α-羟烷基自由基还原，所得半醌与分子氧反应形成超氧化物，二级速率常数为1.3 × 108 dm 3 mol−1 s−1，说明氧化还原循环的潜力。2，2，5，7，8-五甲基-6-羟基苯并二氢吡喃醌（PMHC-Q）的光照（UV-A，355 nm）导致反应性短寿命（约10−6 s）三重态，能够以大于109 dm 3 mol−1 s−1的二级速率常数氧化色氨酸。这些醌的三重态敏化单线态氧的形成，量子产率约为0.8。α-生育酚醌的这种潜在破坏性反应可能部分解释了最近的研究结果，即高水平的膳食维生素E补充剂缺乏任何有益的作用，并可能导致总体死亡率水平略有提高。
Three potential routes to generation of reactive oxygen species from α-tocopherolquinone have been identified. The quinone of the water-soluble vitamin E analogue Trolox C (Trol-Q) is reduced by hydrated electron and isopropanol α-hydroxyalkyl radical, and the resulting semiquinone reacts with molecular oxygen to form superoxide with a second order rate constant of 1.3 × 108 dm3 mol−1 s−1, illustrating the potential for redox cycling. Illumination (UV-A, 355 nm) of the quinone of 2,2,5,7,8-pentamethyl-6-hydroxychromanol (PMHC-Q) leads to a reactive short-lived (ca 10−6 s) triplet state, able to oxidise tryptophan with a second order rate constant greater than 109 dm3 mol−1 s−1. The triplet states of these quinones sensitize singlet oxygen formation with quantum yields of about 0.8. Such potentially damaging reactions of α-tocopherolquinone may in part account for the recent findings that high levels of dietary vitamin E supplementation lack any beneficial effect and may lead to slightly enhanced levels of overall mortality.