Effects of reaction environments on radical-scavenging mechanisms of ascorbic acid
Effects of reaction environments on radical-scavenging mechanisms of ascorbic acid
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DOI：
10.3164/jcbn.20-147
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发表时间：
2021-03-01
影响因子：
2.4
通讯作者：
Fukuzumi, Shunichi
中科院分区：
文献类型：
--
作者：
Nakanishi, Ikuo;Shoji, Yoshimi;Fukuzumi, Shunichi
以2，2-二苯基-1-苦基肼自由基(DPPH中心点)为反应模型，研究了反应环境对抗坏血酸(Asch(2))清除自由基机理的影响。用β-环糊精(β-CD)在水中增溶不溶于水的DPPH中心点。Asch(2)在甲醇(MeOH)中对DPPH中心网点的清除速率远低于在磷酸盐缓冲液中(0.05M，pH 7.0)。有机可溶性5，6-异丙叉-抗坏血酸(iAscH(2))在乙腈(MeCN)中清除DPPH中心的速度比在甲醇中慢得多。在甲醇中，Mg(ClO4)(2)显著抑制Asch(2)和iAscH(2)清除DPPH中心斑点的反应，而在MeCN中则不影响。在磷酸盐缓冲液(0.05M，pH 6.5)中，添加0.05M(ClO4)(2)使Asch(2)-DPPH中心点/β-CD体系的pH变化为6.5，但加入0.05M(ClO4)(2)后，Asch(2)与β-CD增溶的DPPH中心点(DPPH中心点/β-CD)在磷酸盐缓冲液中的反应速度明显加快。因此，在磷酸盐缓冲溶液中，iAscH(2)对DPPH中心点的清除反应可能是通过一步氢原子转移进行的，而Asch(2)与DPPH中心点/β-CD在磷酸盐缓冲溶液中的反应可能涉及电子转移途径。这些结果表明，Asch(2)的DPPH中心清除机理受反应环境的影响。
The effects of reaction environments on the radical-scavenging mechanisms of ascorbic acid (AscH(2)) were investigated using 2,2-diphenyl-1-picrylhydrazyl radical (DPPH center dot) as a reactivity model of reactive oxygen species. Water-insoluble DPPH center dot was solubilized by beta-cyclodextrin (beta-CD) in water. The DPPH center dot-scavenging rate of AscH(2) in methanol (MeOH) was much slower than that in phosphate buffer (0.05 M, pH 7.0). An organic soluble 5,6-isopropylidene-Lascorbic acid (iAscH(2)) scavenged DPPH center dot much slower in acetonitrile (MeCN) than in MeOH. In MeOH, Mg(ClO4)(2) significantly decelerated the DPPH center dot-scavenging reaction by AscH(2) and iAscH(2), while no effect of Mg(ClO4)(2) was observed in MeCN. On the other hand, Mg(ClO4)(2) significantly accelerated the reaction between AscH(2) and beta-CD-solubilized DPPH center dot (DPPH center dot/beta-CD) in phosphate buffer (0.05 M, pH 6.5), although the addition of 0.05 M Mg(ClO4)(2) to the AscH(2)-DPPH center dot/beta-CD system in phosphate buffer (0.05 M, pH 7.0) resulted in the change in pH of the phosphate buffer to be 6.5. Thus, the DPPH center dot-scavenging reaction by iAscH(2) in MeCN may proceed via a one-step hydrogen-atom transfer, while an electrontransfer pathway is involved in the reaction between AscH(2) and DPPH center dot/beta-CD in phosphate buffer solution. These results demonstrate that the DPPH center dot-scavenging mechanism of AscH(2) are affected by the reaction environments.