@article{oai:repo.qst.go.jp:00080715,
 author = {Nakanishi, Ikuo and Shoji, Yoshimi and Ohkubo, Kei and Fukuhara, Kiyoshi and Ozawa, Toshihiko and Ken-ichiro, Matsumoto and Fukuzumi, Shunichi and Ikuo, Nakanishi and Yoshimi, Shoji and Kei, Ohkubo and Toshihiko, Ozawa and Kenichiro, Matsumoto},
 issue = {2},
 journal = {Journal of Clinical Biochemistry and Nutrition},
 month = {Mar},
 note = {The effect of reaction environment on the radical-scavenging mechanism of ascorbic acid (AscH2) was investigated using 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) as a reactivity model of reactive oxygen species. Water-insoluble DPPH was solubilized by beta-cyclodextrin (beta-CD) in water to use DPPH in phosphate buffer solutions. The DPPH-scavenging rate of AscH2 in methanol (MeOH) was much slower than that in phosphate buffer (0.05 M, pH 7.0), where AscH2 undergoes deprotonation to produced ascorbate anion (AscH-). An organic soluble 5,6-isopropylidene-L-ascorbic acid (iAscH2) was also used to compare the DPPH-scavenging reactivity in MeOH and acetonitrile (MeCN). iAscH2 scavenged DPPH much slower in MeCN than in MeOH. In MeOH, Mg(ClO4)2 significantly decelerated the DPPH-scavenging reaction by AscH2 and iAscH2, while no effect of Mg(ClO4)2 on the rate of the reaction of iAscH2 with DPPH was observed in MeCN. On the other hand, Mg(ClO4)2 significantly accelerated the reaction between AscH2 and beta-CD-solubilized DPPH (DPPH/beta-CD) in phosphate buffer (0.05 M, pH 6.5), although the addition of 0.05 M Mg(ClO4)2 to the AscH2-DPPH/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, DPPH-scavenging reaction by iAscH2 in MeCN may proceed via a one-step hydrogen-atom transfer as the rate-determining step, while an electron transfer pathway is partly involved in the reaction between AscH2 and DPPH/beta-CD in phosphate buffer solution, although the detailed mechanism for the deceleration effect of Mg(ClO4)2 in MeOH is under investigation. These results demonstrate that the DPPH-scavenging mechanism by AscH2 are affected by the reaction environments.},
 pages = {116--122},
 title = {Effects of Reaction Environments on Radical-Scavenging Mechanisms of Ascorbic Acid},
 volume = {68},
 year = {2021}
}