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Roque JPL, Nunes CM, Schreiner PR, Fausto R. Hydrogen Tunneling Exhibiting Unexpectedly Small Primary Kinetic Isotope Effects. Chemistry 2024; 30:e202401323. [PMID: 38709063 DOI: 10.1002/chem.202401323] [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: 04/03/2024] [Revised: 04/29/2024] [Accepted: 05/06/2024] [Indexed: 05/07/2024]
Abstract
Probing quantum mechanical tunneling (QMT) in chemical reactions is crucial to understanding and developing new transformations. Primary H/D kinetic isotopic effects (KIEs) beyond the semiclassical maximum values of 7-10 (room temperature) are commonly used to assess substantial QMT contributions in one-step hydrogen transfer reactions, because of the much greater QMT probability of protium vs. deuterium. Nevertheless, we report here the discovery of a reaction model occurring exclusively by H-atom QMT with residual primary H/D KIEs. 2-Hydroxyphenylnitrene, generated in N2 matrix, was found to isomerize to an imino-ketone via sequential (domino) QMT involving anti to syn OH-rotamerization (rate determining step) and [1,4]-H shift reactions. These sequential QMT transformations were also observed in the OD-deuterated sample, and unexpected primary H/D KIEs between 3 and 4 were measured at 3 to 20 K. Analogous residual primary H/D KIEs were found in the anti to syn OH-rotamerization QMT of 2-cyanophenol in a N2 matrix. Evidence strongly indicates that these intriguing isotope-insensitive QMT reactivities arise due to the solvation effects of the N2 matrix medium, putatively through coupling with the moving H/D tunneling particle. Should a similar scenario be extrapolated to conventional solution conditions, then QMT may have been overlooked in many chemical reactions.
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Affiliation(s)
- José P L Roque
- University of Coimbra, CQC-IMS, Department of Chemistry, 3004-535, Coimbra, Portugal
- Institute of Organic Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, 35392, Giessen, Germany
| | - Cláudio M Nunes
- University of Coimbra, CQC-IMS, Department of Chemistry, 3004-535, Coimbra, Portugal
| | - Peter R Schreiner
- Institute of Organic Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, 35392, Giessen, Germany
| | - Rui Fausto
- University of Coimbra, CQC-IMS, Department of Chemistry, 3004-535, Coimbra, Portugal
- Faculty Sciences and Letters, Department of Physics, Istanbul Kultur University, Bakirkoy, Istanbul, 34158, Turkey
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Li X, Ouyang X, Chen B, Liu S, Zeng J. Linkage and Stereochemistry Characters of Phenolic Antioxidant Product Formation. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2023; 71:5382-5390. [PMID: 36693163 DOI: 10.1021/acs.jafc.2c06563] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
The present study developed a smart and novel strategy to elucidate the linkage and stereochemistry characters during phenolic antioxidant product formation. A series of phenolic isomers or analogues were treated with 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide radical, to create 16 antioxidant dimerization reactions in aqueous solution. The products were rapidly identified by ultraperformance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass-spectrometry. Through a systematic function-structure relationship analysis of these reactions and theoretical calculations, it is concluded that the phenolic antioxidant product is formed via linear linkage or furanocyclic linkage. The linear linkage is fulfilled via a radical coupling and controlled by the O-O linkage exclusion, meta-linkage exclusion, and catechol-activated principles. However, when an exocyclic π-bond conjugates with the phenolic core and is affixed at the -OH para-position, the furanocyclic linkage may occur via a subsequent intramolecular Michael addition. The intramolecular addition always lacks Re-attack to show "α,β diastereoselectivity." The α,β diastereoselectivity is the stereochemistry character of furanocyclic linkage during phenolic antioxidant product formation. All these novel findings can benefit not only the field food science but also other fields as well.
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Affiliation(s)
- Xican Li
- School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Guangzhou Higher Education Mega Center, Waihuang East Road No. 232, Guangzhou510006, People's Republic of China
| | - Xiaojian Ouyang
- School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Guangzhou Higher Education Mega Center, Waihuang East Road No. 232, Guangzhou510006, People's Republic of China
| | - Ban Chen
- School of Biological Engineering and Food, Hubei University of Technology, Wuhan430068, People's Republic of China
| | - Shuqin Liu
- School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Guangzhou Higher Education Mega Center, Waihuang East Road No. 232, Guangzhou510006, People's Republic of China
| | - Jingyuan Zeng
- School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Guangzhou Higher Education Mega Center, Waihuang East Road No. 232, Guangzhou510006, People's Republic of China
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Nachliel E, Gutman M. Reaction within the coulomb-cage; science in retrospect. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2023; 1865:184071. [PMID: 36244436 DOI: 10.1016/j.bbamem.2022.184071] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Revised: 08/01/2022] [Accepted: 09/30/2022] [Indexed: 11/06/2022]
Abstract
The Coulomb-cage is defined as the space where the electrostatic interaction between two bodies is more intensive than the thermal energy (kBT). For small molecule, the Coulomb-cage is a small sphere, extending only few water molecules towards the bulk and its radius is sensitive to the ionic strength of the solution. For charged proteins or membranal structures, the Coulomb-cage can engulf large fraction of the surface and provides a preferred pathway for ion propagation along the surface. Similarly, electrostatic potential at the inner space of a channel can form preferential trajectories passage for ions. The dynamics of ions inside the Coulomb-cage of ions was formulated by the studies of proton-anion recombination of excited photoacids. In the present article, we recount the study of intra- Coulomb-cage reaction taking place on the surface of macro-molecular bodies like micelles, membranes, proteins and intra-protein cavities. The study progressed stepwise, tracing the dynamics of a proton ejected from a photo-acid molecule located at defined sites (on membrane, inter-membrane space, active site of enzyme, inside Large Pore Channels etc.). Accumulation of experimental observations encouraged us to study of the reaction mechanism by molecular dynamics simulations of ions within the Coulomb-cage of proteins surface or inside large pores. The intra-Coulomb-cage proton transfer events follows closely the fine structure of the electrostatic field inside the cage and reflects the shape of nearby dielectric boundaries, the temporal ordering of the solvent molecules and the structural fluctuations of the charged side chains. The article sums some 40 years of research, which in retrospect clarifies the intra-Coulomb-cage reaction mechanism.
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Affiliation(s)
- E Nachliel
- Laser Laboratory for Fast Reactions, Dep. Of Biochemistry and Molecular Biology, Life Sciences, Tel Aviv University, Israel
| | - M Gutman
- Laser Laboratory for Fast Reactions, Dep. Of Biochemistry and Molecular Biology, Life Sciences, Tel Aviv University, Israel.
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4
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Lei Y, Zhu W, Zhang Y, Hu Q, Dong J, Hu Y. Benzisoxazole core and benzoxazolopyrrolidine via HDDA-derived benzyne with PTIO/DMPO. CHINESE CHEM LETT 2022. [DOI: 10.1016/j.cclet.2022.107778] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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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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Gao X, Yu XY, Chang CR. Perceptions on the Treatment of Apparent Isotope Effects during the Analyses of Reaction Rate and Mechanism. Phys Chem Chem Phys 2022; 24:15182-15194. [DOI: 10.1039/d2cp00825d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Isotope substitution, a compelling tool of physical chemistry, has been broadly applied in the research field of heterogeneous catalysis. In general, upon the differences in mass-related atomic vibrational frequencies and...
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Nakanishi I, Shoji Y, Ohkubo K, Fukuzumi S. Tunneling in the Hydrogen-Transfer Reaction from a Vitamin E Analog to an Inclusion Complex of 2,2-Diphenyl-1-picrylhydrazyl Radical with β-Cyclodextrin in an Aqueous Buffer Solution at Ambient Temperature. Antioxidants (Basel) 2021; 10:1966. [PMID: 34943069 PMCID: PMC8750123 DOI: 10.3390/antiox10121966] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 12/03/2021] [Accepted: 12/06/2021] [Indexed: 11/16/2022] Open
Abstract
Recently, increasing attention has been paid to quantum mechanical behavior in biology. In this study, we investigated the involvement of quantum mechanical tunneling in the hydrogen-transfer reaction from Trolox, a water-soluble analog of vitamin E (α-tocopherol), to 2,2-diphenyl-1-picrylhydrazyl radical (DPPH•) in a phosphate buffer solution (0.05 M, pH 7.0). DPPH• was used as a reactivity model of reactive oxygen species and solubilized in water using β-cyclodextrin (β-CD). The second-order rate constants, kH and kD, in 0.05 M phosphate buffer solutions prepared with H2O (pH 7.0) and D2O (pD 7.0), respectively, were determined for the reaction between Trolox and DPPH•, using a stopped-flow technique at various temperatures (283-303 K). Large kinetic isotope effects (KIE, kH/kD) were observed for the hydrogen-transfer reaction from Trolox to the β-CD-solubilized DPPH• in the whole temperature range. The isotopic ratio of the Arrhenius prefactor (AH/AD = 0.003), as well as the isotopic difference in the activation energies (19 kJ mol-1), indicated that quantum mechanical tunneling plays a role in the reaction.
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Grants
- 18K06620 Ministry of Education, Culture, Sports, Science and Technology
- 20H02779 Ministry of Education, Culture, Sports, Science and Technology
- 20H04819 Ministry of Education, Culture, Sports, Science and Technology
- 18H04650 Ministry of Education, Culture, Sports, Science and Technology
- 17H03010 Ministry of Education, Culture, Sports, Science and Technology
- 16H02268 Ministry of Education, Culture, Sports, Science and Technology
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Affiliation(s)
- Ikuo Nakanishi
- Quantum RedOx Chemistry Group, 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 Group, 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 Group, 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, 2-8 Yamada-oka, Suita, Osaka 565-0871, Japan
| | - Shunichi Fukuzumi
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
- Faculty of Science and Engineering, Meijo University, Nagoya 468-8502, Japan
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8
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Fukuzumi S, Lee Y, Nam W. Deuterium kinetic isotope effects as redox mechanistic criterions. B KOREAN CHEM SOC 2021. [DOI: 10.1002/bkcs.12417] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Shunichi Fukuzumi
- Department of Chemistry and Nano Science Ewha Womans University Seoul Korea
- Faculty of Science and Engineering Meijo University Nagoya Aichi Japan
| | - Yong‐Min Lee
- Department of Chemistry and Nano Science Ewha Womans University Seoul Korea
- Research Institute for Basic Sciences Ewha Womans University Seoul Korea
| | - Wonwoo Nam
- Department of Chemistry and Nano Science Ewha Womans University Seoul Korea
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9
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Coutinho ND, Machado HG, Carvalho-Silva VH, da Silva WA. Reply to the 'Comment on "Topography of the Free Energy Landscape on the Claisen-Schmidt Condensation: Solvent and Temperature Effect in the Rate-Controlling Step"' by N. D. Coutinho, H. G. Machado, V. H. Carvalho-Silva and W. A. da Silva, Phys. Chem. Chem. Phys., 2021, 23, 6738. Phys Chem Chem Phys 2021; 23:22202-22206. [PMID: 34614051 DOI: 10.1039/d1cp02799a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In the Comment on our paper on the description of the Gibbs Free energy profile of Claisen-Schmidt condensation, it is claimed that our calculations are flawed due to inconsistencies with experimental isotope effects in aqueous acetonitrile. In this Reply, we presented rigorous arguments, ambiguities in the Comment and new calculations confirming the consistency of our results: (i) small differences in the relative energetic barriers in both experimental and theoretical curves make the assignment of the rate-limiting step debatable, making the concept of RCS questionable; (ii) it is shown how the misinterpretation of the elementary steps and of the overall processes rate constants led the Comment to incorrect conclusions about the behavior of the inverse isotopic effect; (iii) neglect in the Comment of the inverse kinetic isotope effect in step R2 due to the hybridization conversion, and of the inverse equilibrium isotopic effect for step R1 to describe an overall iKIE > 1, (iv) an erroneous suggestion in the Comment that the disagreement between experimental kinetic parameters is due to the fact that acetonitrile is not used in previous experimental works, when contradictorily the literature recommends it as being indispensable to allow kinetic accuracy; and (v) new calculations improved by explicit-implicit hybrid treatment again ensure that step R4, and not step R5, can assume the role of RCS in protic solvents. Recognizing that questioning is an excellent path for promoting understanding, we hope that the answers provided here will help to clarify and expand the pertinent topics under discussion.
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Affiliation(s)
- Nayara Dantas Coutinho
- Laboratory of Bioactive Compounds Synthesis N.T.S., University of Brasilia (IQ-UnB), Campus Universitário Darcy Ribeiro, Brasília, DF, Brazil.
| | - Hugo Gontijo Machado
- Modeling of Physical and Chemical Transformations Division, Theoretical and Structural Chemistry Group, Research and Graduate Center, Goias State University, 75132-903, Anapolis, Brazil.
| | - Valter Henrique Carvalho-Silva
- Modeling of Physical and Chemical Transformations Division, Theoretical and Structural Chemistry Group, Research and Graduate Center, Goias State University, 75132-903, Anapolis, Brazil.
| | - Wender Alves da Silva
- Laboratory of Bioactive Compounds Synthesis N.T.S., University of Brasilia (IQ-UnB), Campus Universitário Darcy Ribeiro, Brasília, DF, Brazil.
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Yang L, Liu Y, Zhang W, Hua Y, Chen B, Wu Q, Chen D, Liu S, Li X. Ferroptosis-Inhibitory Difference between Chebulagic Acid and Chebulinic Acid Indicates Beneficial Role of HHDP. Molecules 2021; 26:4300. [PMID: 34299576 PMCID: PMC8303713 DOI: 10.3390/molecules26144300] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Revised: 07/07/2021] [Accepted: 07/12/2021] [Indexed: 01/18/2023] Open
Abstract
The search for a safe and effective inhibitor of ferroptosis, a recently described cell death pathway, has attracted increasing interest from scientists. Two hydrolyzable tannins, chebulagic acid and chebulinic acid, were selected for the study. Their optimized conformations were calculated using computational chemistry at the B3LYP-D3(BJ)/6-31G and B3LYP-D3(BJ)/6-311 + G(d,p) levels. The results suggested that (1) chebulagic acid presented a chair conformation, while chebulinic acid presented a skew-boat conformation; (2) the formation of chebulagic acid requires 762.1729 kcal/mol more molecular energy than chebulinic acid; and (3) the 3,6-HHDP (hexahydroxydiphenoyl) moiety was shown to be in an (R)- absolute stereoconfiguration. Subsequently, the ferroptosis inhibition of both tannins was determined using a erastin-treated bone marrow-derived mesenchymal stem cells (bmMSCs) model and compared to that of ferrostatin-1 (Fer-1). The relative inhibitory levels decreased in the following order: Fer-1 > chebulagic acid > chebulinic acid, as also revealed by the in vitro antioxidant assays. The UHPLC-ESI-Q-TOF-MS analysis suggested that, when treated with 16-(2-(14-carboxytetradecyl)-2-ethyl-4,4-dimethyl-3-oxazolidinyloxy free radicals, Fer-1 generated dimeric products, whereas the two acids did not. In conclusion, two hydrolyzable tannins, chebulagic acid and chebulinic acid, can act as natural ferroptosis inhibitors. Their ferroptosis inhibition is mediated by regular antioxidant pathways (ROS scavenging and iron chelation), rather than the redox-based catalytic recycling pathway exhibited by Fer-1. Through antioxidant pathways, the HHDP moiety in chebulagic acid enables ferroptosis-inhibitory action of hydrolyzable tannins.
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Affiliation(s)
- Lin Yang
- School of Basic Medical Science, Guangzhou University of Chinese Medicine, Waihuan East Road No. 232, Guangzhou 510006, China; (L.Y.); (D.C.)
| | - Yangping Liu
- The Fourth Clinical Medical College, Guangzhou University of Chinese Medicine, Waihuan East Road No. 232, Guangzhou 510006, China;
| | - Wenhui Zhang
- School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Waihuan East Road No. 232, Guangzhou 510006, China; (W.Z.); (Y.H.); (B.C.); (Q.W.); (S.L.)
| | - Yujie Hua
- School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Waihuan East Road No. 232, Guangzhou 510006, China; (W.Z.); (Y.H.); (B.C.); (Q.W.); (S.L.)
| | - Ban Chen
- School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Waihuan East Road No. 232, Guangzhou 510006, China; (W.Z.); (Y.H.); (B.C.); (Q.W.); (S.L.)
| | - Quanzhou Wu
- School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Waihuan East Road No. 232, Guangzhou 510006, China; (W.Z.); (Y.H.); (B.C.); (Q.W.); (S.L.)
| | - Dongfeng Chen
- School of Basic Medical Science, Guangzhou University of Chinese Medicine, Waihuan East Road No. 232, Guangzhou 510006, China; (L.Y.); (D.C.)
| | - Shuqin Liu
- School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Waihuan East Road No. 232, Guangzhou 510006, China; (W.Z.); (Y.H.); (B.C.); (Q.W.); (S.L.)
| | - Xican Li
- School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Waihuan East Road No. 232, Guangzhou 510006, China; (W.Z.); (Y.H.); (B.C.); (Q.W.); (S.L.)
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Antioxidant product analysis of Folium Hibisci Mutabilis. JOURNAL OF SAUDI CHEMICAL SOCIETY 2021. [DOI: 10.1016/j.jscs.2021.101272] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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12
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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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Nguyen QV, Frisbie CD. Hopping Conductance in Molecular Wires Exhibits a Large Heavy-Atom Kinetic Isotope Effect. J Am Chem Soc 2021; 143:2638-2643. [PMID: 33587628 DOI: 10.1021/jacs.0c12244] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
We report a large kinetic isotope effect (KIE) for intramolecular charge transport in π-conjugated oligophenyleneimine (OPI) molecules connected to Au electrodes. 13C and 15N substitution on the imine bonds produces a conductance KIE of ∼2.7 per labeled atom in long OPI wires >4 nm in length, far larger than typical heavy-atom KIEs for chemical reactions. In contrast, isotopic labeling in shorter OPI wires <4 nm does not produce a conductance KIE, consistent with a direct tunneling mechanism. Temperature-dependent measurements reveal that conductance for a long 15N-substituted OPI wire is activated, and we propose that the exceptionally large conductance KIEs imply a thermally assisted, through-barrier polaron tunneling mechanism. In general, observation of large conductance KIEs opens up considerable opportunities for understanding microscopic conduction mechanisms in π-conjugated molecules.
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Affiliation(s)
- Quyen Van Nguyen
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - C Daniel Frisbie
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, United States
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Chen B, Li X, Ouyang X, Liu J, Liu Y, Chen D. Comparison of Ferroptosis-Inhibitory Mechanisms between Ferrostatin-1 and Dietary Stilbenes (Piceatannol and Astringin). Molecules 2021; 26:1092. [PMID: 33669598 PMCID: PMC7922211 DOI: 10.3390/molecules26041092] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2021] [Revised: 02/10/2021] [Accepted: 02/10/2021] [Indexed: 12/17/2022] Open
Abstract
Synthetic arylamines and dietary phytophenolics could inhibit ferroptosis, a recently discovered regulated cell death process. However, no study indicates whether their inhibitory mechanisms are inherently different. Herein, the ferroptosis-inhibitory mechanisms of selected ferrostatin-1 (Fer-1) and two dietary stilbenes (piceatannol and astringin) were compared. Cellular assays suggested that the ferroptosis-inhibitory and electron-transfer potential levels decreased as follows: Fer-1 >> piceatannol > astringin; however, the hydrogen-donating potential had an order different from that observed by the antioxidant experiments and quantum chemistry calculations. Quantum calculations suggested that Fer-1 has a much lower ionization potential than the two stilbenes, and the aromatic N-atoms were surrounded by the largest electron clouds. By comparison, the C4'O-H groups in the two stilbenes exhibited the lowest bond disassociation enthalpies. Finally, the three were found to produce corresponding dimer peaks through ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry analysis. In conclusion, Fer-1 mainly depends on the electron transfer of aromatic N-atoms to construct a redox recycle. However, piceatannol and astringin preferentially donate hydrogen atoms at the 4'-OH position to mediate the conventional antioxidant mechanism that inhibits ferroptosis, and to ultimately form dimers. These results suggest that dietary phytophenols may be safer ferroptosis inhibitors for balancing normal and ferroptotic cells than arylamines with high electron-transfer potential.
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Affiliation(s)
- Ban Chen
- School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Guangzhou 510006, China; (B.C.); (X.O.)
| | - Xican Li
- School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Guangzhou 510006, China; (B.C.); (X.O.)
| | - Xiaojian Ouyang
- School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Guangzhou 510006, China; (B.C.); (X.O.)
| | - Jie Liu
- School of Basic Medical Science, Guangzhou University of Chinese Medicine, Guangzhou 510006, China;
- The Research Center of Basic Integrative Medicine, Guangzhou University of Chinese Medicine, Guangzhou 510006, China
| | - Yangping Liu
- The Fourth Clinical Medical College, Guangzhou University of Chinese Medicine, Waihuan East Road No. 232, Guangzhou Higher Education Mega Center, Guangzhou 510006, China;
| | - Dongfeng Chen
- School of Basic Medical Science, Guangzhou University of Chinese Medicine, Guangzhou 510006, China;
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