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Nakanishi I, Shoji Y, Ohkubo K, Ito H, Fukuzumi S. Water-Induced Regeneration of a 2,2-Diphenyl-1-picrylhydrazyl Radical after Its Scandium Ion-Promoted Electron-Transfer Disproportionation in an Aprotic Medium. Molecules 2023; 28:5002. [PMID: 37446663 DOI: 10.3390/molecules28135002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 06/14/2023] [Accepted: 06/23/2023] [Indexed: 07/15/2023] Open
Abstract
A neutral, stable radical, 2,2-diphenyl-1-picrylhydrazyl radical (DPPH•), has been frequently used to estimate the activity of antioxidants for more than 60 years. However, the number of reports about the effect of metal ions on the reactivity of DPPH• is quite limited. We have recently reported a unique electron-transfer disproportionation of DPPH• to produce the DPPH cations (DPPH+) and anions (DPPH-) upon the addition of scandium triflate [Sc(OTf)3 (OTf = OSO2CF3)] to an acetonitrile (MeCN) solution of DPPH•. The driving force of this reaction is suggested to be an interaction between DPPH- and Sc3+. In this study, it is demonstrated that the addition of H2O to the DPPH•-Sc(OTf)3 system in MeCN resulted in an increase in the absorption band at 519 nm due to DPPH•. This indicated that an electron-transfer comproportionation occurred to regenerate DPPH•. The regeneration of DPPH• was also confirmed by electron paramagnetic resonance (EPR) spectroscopy. The amount of DPPH• increased with an increasing amount of added H2O to reach a constant value. The detailed mechanism of regeneration of DPPH• was proposed based on the detailed spectroscopic and kinetic analyses, in which the reaction of DPPH+ with [(DPPH)2Sc(H2O)3]+ generated upon the addition of H2O to [(DPPH)2Sc]+ is the rate-determining step.
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Grants
- JP18K06620 Ministry of Education, Culture, Sports, Science and Technology
- JP20H02779 Ministry of Education, Culture, Sports, Science and Technology
- JP20H04819 Ministry of Education, Culture, Sports, Science and Technology
- JP18H04650 Ministry of Education, Culture, Sports, Science and Technology
- JP17H03010 Ministry of Education, Culture, Sports, Science and Technology
- JP16H02268 Ministry of Education, Culture, Sports, Science and Technology
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Affiliation(s)
- Ikuo Nakanishi
- Quantum RedOx Chemistry Team, Institute for Quantum Life Science (iQLS), Quantum Life and Medical Science Directorate, National Institutes for Quantum Science and Technology (QST), Inage-ku, Chiba 263-8555, Japan
| | - Yoshimi Shoji
- Quantum RedOx Chemistry Team, Institute for Quantum Life Science (iQLS), Quantum Life and Medical Science Directorate, National Institutes for Quantum Science and Technology (QST), Inage-ku, Chiba 263-8555, Japan
| | - Kei Ohkubo
- Quantum RedOx Chemistry Team, Institute for Quantum Life Science (iQLS), Quantum Life and Medical Science Directorate, National Institutes for Quantum Science and Technology (QST), Inage-ku, Chiba 263-8555, Japan
- Institute for Advanced Co-Creation Studies, Open and Transdisciplinary Research Initiatives, Osaka University, Suita 565-0871, Japan
| | - Hiromu Ito
- Quantum RedOx Chemistry Team, Institute for Quantum Life Science (iQLS), Quantum Life and Medical Science Directorate, National Institutes for Quantum Science and Technology (QST), Inage-ku, Chiba 263-8555, Japan
| | - Shunichi Fukuzumi
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Republic of Korea
- Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571, Japan
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Matsumoto KI, Nakanishi I, Zhelev Z, Bakalova R, Aoki I. Nitroxyl Radical as a Theranostic Contrast Agent in Magnetic Resonance Redox Imaging. Antioxid Redox Signal 2022; 36:95-121. [PMID: 34148403 PMCID: PMC8792502 DOI: 10.1089/ars.2021.0110] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Significance:In vivo assessment of paramagnetic and diamagnetic conversions of nitroxyl radicals based on cyclic redox mechanism can be an index of tissue redox status. The redox mechanism of nitroxyl radicals, which enables their use as a normal tissue-selective radioprotector, is seen as being attractive on planning radiation therapy. Recent Advances:In vivo redox imaging using nitroxyl radicals as redox-sensitive contrast agents has been developed to assess tissue redox status. Chemical and biological behaviors depending on chemical structures of nitroxyl radical compounds have been understood in detail. Polymer types of nitroxyl radical contrast agents and/or nitroxyl radical-labeled drugs were designed for approaching theranostics. Critical Issues: Nitroxyl radicals as magnetic resonance imaging (MRI) contrast agents have several advantages compared with those used in electron paramagnetic resonance (EPR) imaging, while support by EPR spectroscopy is important to understand information from MRI. Redox-sensitive paramagnetic contrast agents having a medicinal benefit, that is, nitroxyl-labeled drug, have been developed and proposed. Future Directions: A development of suitable nitroxyl contrast agent for translational theranostic applications with high reaction specificity and low normal tissue toxicity is under progress. Nitroxyl radicals as redox-sensitive magnetic resonance contrast agents can be a useful tool to detect an abnormal tissue redox status such as disordered oxidative stress. Antioxid. Redox Signal. 36, 95-121.
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Affiliation(s)
- Ken-Ichiro Matsumoto
- Quantitative RedOx Sensing Group, Department of Radiation Regulatory Science Research, National Institute of Radiological Sciences, Quantum Life and Medical Science Directorate, National Institutes for Quantum and Radiological Science and Technology, Chiba-shi, Japan
| | - Ikuo Nakanishi
- Quantum RedOx Chemistry Group, Institute for Quantum Life Science, Quantum Life and Medical Science Directorate, National Institutes for Quantum and Radiological Science and Technology, Chiba-shi, Japan
| | - Zhivko Zhelev
- Medical Faculty, Trakia University, Stara Zagora, Bulgaria.,Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Sofia, Bulgaria
| | - Rumiana Bakalova
- Functional and Molecular Imaging Goup, Department of Molecular Imaging and Theranostics, Institute for Quantum Medical Science, Quantum Life and Medical Science Directorate, National Institutes for Quantum and Radiological Science and Technology, Chiba-shi, Japan
| | - Ichio Aoki
- Functional and Molecular Imaging Goup, Department of Molecular Imaging and Theranostics, Institute for Quantum Medical Science, Quantum Life and Medical Science Directorate, National Institutes for Quantum and Radiological Science and Technology, Chiba-shi, Japan
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Nakanishi I, Shoji Y, Ohkubo K, Fukuhara K, Ozawa T, Matsumoto KI, Fukuzumi S. Effects of reaction environments on radical-scavenging mechanisms of ascorbic acid. J Clin Biochem Nutr 2021; 68:116-122. [PMID: 33879962 PMCID: PMC8046006 DOI: 10.3164/jcbn.20-147] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Accepted: 10/11/2020] [Indexed: 11/22/2022] Open
Abstract
The effects of reaction environments on the radical-scavenging mechanisms of ascorbic acid (AscH2) 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 AscH2 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 (iAscH2) scavenged DPPH• much slower in acetonitrile (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 was observed in MeCN. On the other hand, Mg(ClO4)2 significantly accelerated the reaction between AscH2 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(ClO4)2 to the AscH2-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 iAscH2 in MeCN may proceed via a one-step hydrogen-atom transfer, while an electron-transfer pathway is involved in the reaction between AscH2 and DPPH•/β-CD in phosphate buffer solution. These results demonstrate that the DPPH•-scavenging mechanism of AscH2 are affected by the reaction environments.
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Affiliation(s)
- Ikuo Nakanishi
- Quantitative RedOx Sensing Group, Department of Basic Medical Sciences for Radiation Damages, National Institute of Radiological Sciences (NIRS), Quantum Medical Science Directorate, National Institutes for Quantum and Radiological Science and Technology (QST), Inage-ku, Chiba 263-8555, Japan
| | - Yoshimi Shoji
- Quantitative RedOx Sensing Group, Department of Basic Medical Sciences for Radiation Damages, National Institute of Radiological Sciences (NIRS), Quantum Medical Science Directorate, National Institutes for Quantum and Radiological Science and Technology (QST), Inage-ku, Chiba 263-8555, Japan
| | - Kei Ohkubo
- Quantitative RedOx Sensing Group, Department of Basic Medical Sciences for Radiation Damages, National Institute of Radiological Sciences (NIRS), Quantum Medical Science Directorate, National Institutes for Quantum and Radiological Science and Technology (QST), Inage-ku, Chiba 263-8555, Japan
- Institute for Advanced Co-Creation Studies, Open and Transdisciplinary Research Initiatives, Osaka University, Suita, Osaka 565-0871, Japan
| | - Kiyoshi Fukuhara
- School of Pharmacy, Showa University, Shinagawa-ku, Tokyo 142-8555, Japan
| | - Toshihiko Ozawa
- Nihon Pharmaceutical University, Kitaadachi-gun, Saitama 362-0806, Japan
| | - Ken-ichiro Matsumoto
- Quantitative RedOx Sensing Group, Department of Basic Medical Sciences for Radiation Damages, National Institute of Radiological Sciences (NIRS), Quantum Medical Science Directorate, National Institutes for Quantum and Radiological Science and Technology (QST), Inage-ku, Chiba 263-8555, Japan
| | - Shunichi Fukuzumi
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
- Faculty of Science and Engineering, Meijo University, Nagoya, Aichi 468-8502, Japan
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Nakanishi I, Ohkubo K, Shoji Y, Fujitaka Y, Shimoda K, Matsumoto KI, Fukuhara K, Hamada H. Relationship between the radical-scavenging activity of selected flavonols and thermodynamic parameters calculated by density functional theory. Free Radic Res 2020; 54:535-539. [PMID: 32838569 DOI: 10.1080/10715762.2020.1813887] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The relationship between radical-scavenging rate constants (k) in an aprotic medium and thermodynamic parameters calculated by density functional theory (DFT) was investigated for 7 flavonols, which are myricetin (Myr), quercetin (Que), morin (Mor), kaempferol (Kae), 2'-methylquercetin (2'-MeQue), 5'-methylquercetin (5'-MeQue), and 2',5'-dimethylquercetin (Me2Que). The k values were determined for the reaction between the flavonols and galvinoxyl radical used as a reactivity model of reactive oxygen species in deaerated acetonitrile at 298 K. The energy difference values (D HT, HT: hydrogen transfer) between the flavonols and the corresponding radicals, which equal to the relative O-H bond dissociation energies of the OH groups in the flavonols and ionisation potentials (IP) were calculated by DFT at the B3LYP/6-31++G(d) level with C-PCM solvation model parameterised for acetonitrile. Among the 7 flavonols used in this study, calculated IP values of 4 flavonols exhibited a linear correlation with log k, suggesting that the radical-scavenging reaction of these flavonols may proceed via an electron transfer as the rate determining step.
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Affiliation(s)
- Ikuo Nakanishi
- Quantitative RedOx Sensing Group, Department of Basic Medical Sciences for Radiation Damages, National Institute of Radiological Sciences (NIRS), Quantum Medical Science Directorate, National Institutes for Quantum and Radiological Science and Technology (QST), Chiba, Japan
| | - Kei Ohkubo
- Quantitative RedOx Sensing Group, Department of Basic Medical Sciences for Radiation Damages, National Institute of Radiological Sciences (NIRS), Quantum Medical Science Directorate, National Institutes for Quantum and Radiological Science and Technology (QST), Chiba, Japan.,Institute for Advanced Co-Creation Studies, Open and Transdisciplinary Research Initiatives, Osaka University, Osaka, Japan
| | - Yoshimi Shoji
- Quantitative RedOx Sensing Group, Department of Basic Medical Sciences for Radiation Damages, National Institute of Radiological Sciences (NIRS), Quantum Medical Science Directorate, National Institutes for Quantum and Radiological Science and Technology (QST), Chiba, Japan
| | - Yuya Fujitaka
- Department of Life Science, Okayama University of Science, Okayama, Japan
| | - Kei Shimoda
- Department of Biomedical Chemistry, Faculty of Medicine, Oita University, Oita, Japan
| | - Ken-Ichiro Matsumoto
- Quantitative RedOx Sensing Group, Department of Basic Medical Sciences for Radiation Damages, National Institute of Radiological Sciences (NIRS), Quantum Medical Science Directorate, National Institutes for Quantum and Radiological Science and Technology (QST), Chiba, Japan
| | | | - Hiroki Hamada
- Department of Life Science, Okayama University of Science, Okayama, Japan
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Nakanishi I, Kawashima T, Ohkubo K, Waki T, Uto Y, Kamada T, Ozawa T, Matsumoto KI, Fukuzumi S. Disproportionation of a 2,2-diphenyl-1-picrylhydrazyl radical as a model of reactive oxygen species catalysed by Lewis and/or Brønsted acids. Chem Commun (Camb) 2014; 50:814-6. [DOI: 10.1039/c3cc47819j] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Ouchi A, Nagaoka SI, Abe K, Mukai K. Kinetic study of the aroxyl radical-scavenging reaction of alpha-tocopherol in methanol solution: notable effect of the alkali and alkaline earth metal salts on the reaction rates. J Phys Chem B 2009; 113:13322-31. [PMID: 19754085 DOI: 10.1021/jp906425r] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A kinetic study of the aroxyl (ArO*) radical-scavenging reaction of alpha-tocopherol (alpha-TocH) has been performed in the presence of six kinds of alkali and alkaline earth metal salts (LiI, LiClO(4), NaI, NaClO(4), KI, and Mg(ClO(4))(2)) in methanol solution, using stopped-flow spectrophotometry. The decay rate of the ArO* for the reaction of alpha-TocH with ArO* increased linearly with increasing concentration of metal salts. The second-order rate constants (k(s)) for the reaction of alpha-TocH with ArO* increased in the order of no metal salt < KI approximately NaClO(4) approximately NaI <or= LiClO(4) < Mg(ClO(4))(2) < LiI at the same concentration of metal salts. For example, the k(s) values in methanol solution including 4.00 x 10(-1) M of LiI and Mg(ClO(4))(2) were 3.04 and 1.30 times larger than that in the absence of metal salts, respectively. The alkali and alkaline earth metal salts having smaller ionic radius of cation and anion and larger charge of cation gave larger rate constants (k(s)). Effects of metal cations on the UV-vis absorption spectra of the alpha-Toc* (and ArO*) radical were negligible in methanol solution, suggesting that the complex formation between the alpha-Toc* (and ArO*) radical molecule and metal cations is hindered by the hydrogen bond between radical and methanol molecules. The results indicate that the hydrogen transfer reaction of alpha-TocH proceeds via an electron transfer intermediate from alpha-TocH to ArO* radicals followed by proton transfer. Both the coordinations of metal cations to the one-electron reduced anions of ArO* (ArO: (-)) and of counteranions to the one-electron oxidized cations of alpha-TocH (alpha-TocH(+)*) may stabilize the intermediate, resulting in the acceleration of electron transfer. On the other hand, the effect of metal salts on the rate of bimolecular self-reaction (2k(d)) of the alpha-Toc* radical was not observed. The result suggests that the hydrogen transfer reaction between two alpha-Toc* radical molecules proceeds via a one-step hydrogen atom transfer mechanism rather than via an electron-transfer intermediate. High concentrations of alkali and alkaline earth metal salts coexist with alpha-TocH in plasma, blood, and many tissues, suggesting the contribution of the metal salts to the antioxidant actions of alpha-TocH.
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Affiliation(s)
- Aya Ouchi
- Department of Chemistry, Faculty of Science, Ehime University, Matsuyama 790-8577, Japan.
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Manda S, Nakanishi I, Ohkubo K, Kawashima T, Matsumoto KI, Ozawa T, Fukuzumi S, Ikota N, Anzai K. Effect of Solvent Polarity on the One-electron Oxidation of Cyclic Nitroxyl Radicals. CHEM LETT 2007. [DOI: 10.1246/cl.2007.914] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Manda S, Nakanishi I, Ohkubo K, Yakumaru H, Matsumoto KI, Ozawa T, Ikota N, Fukuzumi S, Anzai K. Nitroxyl radicals: electrochemical redox behaviour and structure–activity relationships. Org Biomol Chem 2007; 5:3951-5. [DOI: 10.1039/b714765a] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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