Aroxyl-Radical-Scavenging Rate Increases Remarkably under the Coexistence of α-Tocopherol and Ubiquinol-10 (or Vitamin C): Finding of Synergistic Effect on the Reaction Rate
Aroxyl-Radical-Scavenging Rate Increases Remarkably under the Coexistence of α-Tocopherol and Ubiquinol-10 (or Vitamin C): Finding of Synergistic Effect on the Reaction Rate
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α-生育酚和 Ubiquinol-10（或维生素 C）共存时，Aroxyl 自由基清除率显着增加：发现对反应率的协同效应
DOI：
10.1021/jp403239q
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发表时间：
2013
期刊：
影响因子：
3.3
通讯作者：
and S. Nagaoka
中科院分区：
文献类型：
--
作者：
K. Mukai;A. Ouchi;S. Nakaya;and S. Nagaoka
在2-丙醇/水（2-PrOH/H2O, 5/1, v/v）溶液中测定了抗氧化剂（AOHs） （α-生育酚（α-TocH）、泛醇-10 （UQ10H2）和抗坏血酸钠（Na+AsH -））的aroxyl自由基（ArO•）清除速率常数（ksAOH）。测定了两种AOH （α-TocH和uq10h2）和(ii) α-TocH和Na+AsH -)的混合物的ksaoh值。α-TocH、UQ10H2和Na+AsH -的ksaoh值分别增加1.6倍、2.5倍和6.8倍，具有显著的协同效应。在2-PrOH/H2O溶液中，用uq10h2和Na+ ash2双混流分光光度法测定α-生育酚自由基（α-Toc•）对α-TocH的再生速率。uq10h2和Na+ ash -的二阶速率常数kr分别为2.01 × 105和1.19 × 106M-1s-1。事实上，由于上述快速再生反应，α-TocH与ArO•反应产生的α-Toc•（λmax= 428 nm）在uq10h2o或Na+ ash -存在下，其紫外-可见吸收消失。结果表明，uq10h2o或Na+AsH -共存抑制了α-Toc•的促氧化作用。由于α-TocH、UQ10H2和抗坏血酸单阴离子（AsH -）在血浆、血液和各组织中以较高的浓度共存，上述协同作用，即增加自由基清除率和抑制促氧化反应，可能在生物系统中发挥作用。
Measurements of aroxyl radical (ArO•)-scavenging rate constants (ksAOH) of antioxidants (AOHs) (α-tocopherol (α-TocH), ubiquinol-10 (UQ10H2), and sodium ascorbate (Na+AsH–)) were performed in 2-propanol/water (2-PrOH/H2O, 5/1, v/v) solution using stopped-flow spectrophotometry.ksAOHvalues were measured not only for each AOH but also for the mixtures of two AOHs ((i) α-TocH and UQ10H2and (ii) α-TocH and Na+AsH–). A notable synergistic effect that theksAOHvalues increase 1.6, 2.5, and 6.8 times for α-TocH, UQ10H2, and Na+AsH–, respectively, was observed for the solutions including two kinds of AOHs. Furthermore, measurements of the regeneration rates of α-tocopheroxyl radical (α-Toc•) to α-TocH by UQ10H2and Na+AsH–were performed in 2-PrOH/H2O using double-mixing stopped-flow spectrophotometry. Second-order rate constants (kr) obtained for UQ10H2and Na+AsH–were 2.01 × 105and 1.19 × 106M–1s–1, respectively. In fact, UV–vis absorption of α-Toc•(λmax= 428 nm), which had been produced by reaction of α-TocH with ArO•, disappeared under the existence of UQ10H2or Na+AsH–due to the above fast regeneration reaction. The result indicates that the prooxidant effect of α-Toc•is suppressed by the coexistence of UQ10H2or Na+AsH–. As α-TocH, UQ10H2, and ascorbate monoanion (AsH–) coexist in relatively high concentrations in plasma, blood, and various tissues, the above synergistic effect, that is, the increase of the free-radical-scavenging rate and suppression of the prooxidant reaction, may function in biological systems.