期刊名称：Journal of Clinical Biochemistry and Nutrition
印刷版ISSN：0912-0009
电子版ISSN：1880-5086
出版年度：2021
卷号：68
期号：2
页码：116-122
DOI：10.3164/jcbn.20-147
出版社：The Society for Free Radical Research Japan
摘要：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 • ) as a reactivity model of reactive oxygen species. Water-insoluble DPPH • was solubilized by β-cyclodextrin (β-CD) in water. The DPPH • -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- l -ascorbic acid (iAscH 2 ) scavenged DPPH • much slower in acetonitrile (MeCN) than in MeOH. In MeOH, Mg(ClO 4 ) 2 significantly decelerated the DPPH • -scavenging reaction by AscH 2 and iAscH 2 , while no effect of Mg(ClO 4 ) 2 was observed in MeCN. On the other hand, Mg(ClO 4 ) 2 significantly accelerated the reaction between AscH 2 and β-CD-solubilized DPPH • (DPPH • /β-CD) in phosphate buffer (0.05 M, pH 6.5), although the addition of 0.05 M Mg(ClO 4 ) 2 to the AscH 2 –DPPH • /β-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 • -scavenging reaction by iAscH 2 in MeCN may proceed via a one-step hydrogen-atom transfer, while an electron-transfer pathway is involved in the reaction between AscH 2 and DPPH • /β-CD in phosphate buffer solution. These results demonstrate that the DPPH • -scavenging mechanism of AscH 2 are affected by the reaction environments.
关键词：antioxidant;ascorbic acid;radical;reaction mechanism;hydrogen transfer
