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Farmer LA, Pratt DA. Non-Tertiary Alkyl Substituents Enhance High-Temperature Radical Trapping by Phenothiazine and Phenoxazine Antioxidants. J Org Chem 2024; 89:6126-6137. [PMID: 38619817 DOI: 10.1021/acs.joc.4c00099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/16/2024]
Abstract
Radical-trapping antioxidants (RTAs) are an indispensable class of additive used to preserve hydrocarbon materials from oxidative degradation. Materials that are regularly subjected to elevated temperatures where autoxidation is self-initiated (i.e., >120 °C) require high concentrations of RTA for protection. Not only is this costly, but it can negatively impact material performance. Herein we show that inhibition of the autoxidation of a model hydrocarbon (n-hexadecane) by phenothiazine (PTZ) at ≥160 °C can be greatly enhanced by the incorporation of either 1° or 2° alkyl substituents in the 3- and/or 7-positions of the scaffold. Structure-reactivity studies, product analyses and computations suggest that this results from hydrogen atom transfer (HAT) from the benzylic carbon of these alkyl substituents in the PTZ-derived aminyl radical intermediate. The resultant iminoquinone methide can then undergo further radical-trapping reactions, depending on the nature of the alkyl substituent. Similar structure-reactivity relationships are observed for the phenoxazine (PNX) scaffold. These results not only have significant implications for the design and development of new high-temperature RTA technology, but also for understanding aminic RTA activity at elevated temperatures. Specifically, they suggest that a stoichiometric model better accounts for the RTA activity of aromatic amines in saturated hydrocarbons than the widely accepted catalytic model.
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Affiliation(s)
- Luke A Farmer
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
| | - Derek A Pratt
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
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2
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Hanson CS, Donohoe M, Pratt DA. Enhancement of Diarylamine Antioxidant Activity by Molybdenum Dithiocarbamates. J Org Chem 2023. [PMID: 38051117 DOI: 10.1021/acs.joc.3c02246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/07/2023]
Abstract
Molybdenum dithiocarbamates (MDTCs) are indispensable lubricant additives. Although their role as antiwear agents is well established, they have also been attributed antioxidant properties that are not understood. MDTCs do not inhibit autoxidation, but they markedly enhance the capacity of diphenylamines (DPAs)─ubiquitous radical-trapping antioxidants (RTAs)─to do so. We find this synergy to be evident not only at elevated temperatures (160 °C in n-hexadecane) but also at moderate temperatures, where autoxidations can be continuously monitored and kinetics more easily interpreted (100 °C in squalane). Interestingly, the synergy disappeared in an unsaturated hydrocarbon (n-hexadec-1-ene), where the RTA activity of the DPA is known to result from the diarylnitroxide derived therefrom. Autoxidations of squalane carried out in the presence of the diarylnitroxide─wherein it is a poor inhibitor─were much better inhibited in the presence of MDTC, suggesting that it converts the nitroxide to (a) more competent RTA(s). Indeed, preparative experiments revealed two species: DPA and a DPA dimer into which a single oxygen atom had been incorporated. This conversion is accelerated by the oxidation of MDTC to a dioxo molybdenum species. A mechanism is proposed to account for these observations, and the implications of our findings and their interpretation are discussed.
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Affiliation(s)
- Carly S Hanson
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, 10 Marie Curie Pvt., Ottawa K1N 6N5, Ontario, Canada
| | - Michael Donohoe
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, 10 Marie Curie Pvt., Ottawa K1N 6N5, Ontario, Canada
| | - Derek A Pratt
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, 10 Marie Curie Pvt., Ottawa K1N 6N5, Ontario, Canada
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3
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Mallais M, Hanson CS, Giray M, Pratt DA. General Approach to Identify, Assess, and Characterize Inhibitors of Lipid Peroxidation and Associated Cell Death. ACS Chem Biol 2023; 18:561-571. [PMID: 36854078 DOI: 10.1021/acschembio.2c00897] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/02/2023]
Abstract
Lipid peroxidation (LPO) is associated with a variety of pathologies and drives a form of regulated necrosis called ferroptosis. There is much interest in small-molecule inhibitors of LPO as potential leads for therapeutic development for neurodegeneration, stroke, and acute organ failure, but this has been hampered by the lack of a universal high-throughput assay that can identify and assess candidates. Herein, we describe the development and validation of such an approach. Phosphatidylcholine liposomes loaded with ∼10% phospholipid hydroperoxide and STY-BODIPY, a fluorescent signal carrier that co-autoxidizes with polyunsaturated phospholipids, are shown to autoxidize at convenient and constant rates when subjected to an optimized Fe2+-based initiation cocktail. The use of this initiation system enables the identification of each of the various classes of LPO inhibitors which have been shown to rescue from cell death in ferroptosis: radical-trapping antioxidants (RTAs), peroxidase mimics, and iron chelators. Furthermore, a limited dose-response profile of inhibitors enables the resolution of RTA and non-RTA inhibitors─thereby providing not only relative efficacy but mechanistic information in the same microplate-based experiment. Despite this versatility, the approach can still be used to estimate rate constants for the reaction of RTAs with chain-propagating peroxyl radicals, as demonstrated for a representative panel of RTAs. To illustrate the utility of this assay, we carried out a preliminary investigation of the 'off-target' activity of several ferroptosis suppressors that have been proposed to act independently of inhibition of LPO, including lipoxygenase inhibitors, cannabinoids, and necrostatins, the archetype inhibitors of necroptosis.
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Affiliation(s)
- Melodie Mallais
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa ON K1N 6N5, Canada
| | - Carly S Hanson
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa ON K1N 6N5, Canada
| | - Melanie Giray
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa ON K1N 6N5, Canada
| | - Derek A Pratt
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa ON K1N 6N5, Canada
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4
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Rousselle B, Massot A, Privat M, Dondaine L, Trommenschlager A, Bouyer F, Bayardon J, Ghiringhelli F, Bettaieb A, Goze C, Paul C, Malacea-Kabbara R, Bodio E. Conception and evaluation of fluorescent phosphine-gold complexes: from synthesis to in vivo investigations. ChemMedChem 2022; 17:e202100773. [PMID: 35254001 DOI: 10.1002/cmdc.202100773] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Revised: 03/02/2022] [Indexed: 11/11/2022]
Abstract
A phosphine gold(I) and phosphine-phosphonium gold(I) complexes bearing a fluorescent coumarin moiety were synthesized and characterized. Both complexes displayed interesting photophysical properties: good molar absorption coefficient, good quantum yield of fluorescence, and ability to be tracked in vitro thanks to two-photon imaging. Their in vitro and in vivo biological properties were evaluated onto cancer cell lines both human and murine and into CT26 tumor-bearing BALB/c mice. They displayed moderate to strong antiproliferative properties and the phosphine-phosphonium gold(I) complex induced significant in vivo anti-cancer effect.
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Affiliation(s)
- Benjamin Rousselle
- Université Bourgogne Franche-Comté: Universite Bourgogne Franche-Comte, ICMUB, FRANCE
| | - Aurélie Massot
- EPHE PSL: Ecole Pratique des Hautes Etudes, LIIC, FRANCE
| | - Malorie Privat
- Université Bourgogne Franche-Comté: Universite Bourgogne Franche-Comte, ICMUB and LIIC, FRANCE
| | - Lucile Dondaine
- Université Bourgogne Franche-Comté: Universite Bourgogne Franche-Comte, ICMUB and LIIC, FRANCE
| | | | - Florence Bouyer
- Université Bourgogne Franche-Comté: Universite Bourgogne Franche-Comte, INSERM 1231, FRANCE
| | - Jérôme Bayardon
- Université Bourgogne Franche-Comté: Universite Bourgogne Franche-Comte, ICMUB, FRANCE
| | - François Ghiringhelli
- Université Bourgogne Franche-Comté: Universite Bourgogne Franche-Comte, INSERM UMR 1231, FRANCE
| | - Ali Bettaieb
- EPHE PSL: Ecole Pratique des Hautes Etudes, LIIC, FRANCE
| | - Christine Goze
- Université Bourgogne Franche-Comté: Universite Bourgogne Franche-Comte, ICMUB, FRANCE
| | - Catherine Paul
- EPHE PSL: Ecole Pratique des Hautes Etudes, LIIC, FRANCE
| | | | - Ewen Bodio
- Burgundy University, Institut de Chimie Moleculaire de l'Universite de Bourgogne - UMR CNRS 6302, 9 avenue Alain Savary, BP 47870, 21078, Dijon, FRANCE
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5
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Omran B, Baek KH. Nanoantioxidants: Pioneer Types, Advantages, Limitations, and Future Insights. Molecules 2021; 26:7031. [PMID: 34834124 PMCID: PMC8624789 DOI: 10.3390/molecules26227031] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 11/14/2021] [Accepted: 11/18/2021] [Indexed: 12/12/2022] Open
Abstract
Free radicals are generated as byproducts of normal metabolic processes as well as due to exposure to several environmental pollutants. They are highly reactive species, causing cellular damage and are associated with a plethora of oxidative stress-related diseases and disorders. Antioxidants can control autoxidation by interfering with free radical propagation or inhibiting free radical formation, reducing oxidative stress, improving immune function, and increasing health longevity. Antioxidant functionalized metal nanoparticles, transition metal oxides, and nanocomposites have been identified as potent nanoantioxidants. They can be formulated in monometallic, bimetallic, and multi-metallic combinations via chemical and green synthesis techniques. The intrinsic antioxidant properties of nanomaterials are dependent on their tunable configuration, physico-chemical properties, crystallinity, surface charge, particle size, surface-to-volume ratio, and surface coating. Nanoantioxidants have several advantages over conventional antioxidants, involving increased bioavailability, controlled release, and targeted delivery to the site of action. This review emphasizes the most pioneering types of nanoantioxidants such as nanoceria, silica nanoparticles, polydopamine nanoparticles, and nanocomposite-, polysaccharide-, and protein-based nanoantioxidants. This review overviews the antioxidant potential of biologically synthesized nanomaterials, which have emerged as significant alternatives due to their biocompatibility and high stability. The promising nanoencapsulation nanosystems such as solid lipid nanoparticles, nanostructured lipid carriers, and liposome nanoparticles are highlighted. The advantages, limitations, and future insights of nanoantioxidant applications are discussed.
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Affiliation(s)
- Basma Omran
- Department of Biotechnology, Yeungnam University, Gyeongsan 38541, Gyeongbuk, Korea;
- Department of Processes Design & Development, Egyptian Petroleum Research Institute (EPRI), Cairo 11727, Egypt
| | - Kwang-Hyun Baek
- Department of Biotechnology, Yeungnam University, Gyeongsan 38541, Gyeongbuk, Korea;
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Matos MJ, Uriarte E, Santana L. 3-Phenylcoumarins as a Privileged Scaffold in Medicinal Chemistry: The Landmarks of the Past Decade. Molecules 2021; 26:6755. [PMID: 34771164 PMCID: PMC8587835 DOI: 10.3390/molecules26216755] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Revised: 11/03/2021] [Accepted: 11/05/2021] [Indexed: 12/27/2022] Open
Abstract
3-Phenylcoumarins are a family of heterocyclic molecules that are widely used in both organic and medicinal chemistry. In this overview, research on this scaffold, since 2010, is included and discussed, focusing on aspects related to its natural origin, synthetic procedures and pharmacological applications. This review paper is based on the most relevant literature related to the role of 3-phenylcoumarins in the design of new drug candidates. The references presented in this review have been collected from multiple electronic databases, including SciFinder, Pubmed and Mendeley.
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Affiliation(s)
- Maria J Matos
- Centro de Investigação em Química da Universidade do Porto (CIQUP), Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, 4169-007 Porto, Portugal
- Departamento de Química Orgánica, Facultade de Farmacia, Universidade Santiago de Compostela, 15782 Santiago de Compostela, Spain
| | - Eugenio Uriarte
- Departamento de Química Orgánica, Facultade de Farmacia, Universidade Santiago de Compostela, 15782 Santiago de Compostela, Spain
- Instituto de Ciencias Químicas Aplicadas, Universidad Autónoma de Chile, Santiago 7500912, Chile
| | - Lourdes Santana
- Departamento de Química Orgánica, Facultade de Farmacia, Universidade Santiago de Compostela, 15782 Santiago de Compostela, Spain
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7
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Poon JF, Farmer LA, Haidasz EA, Pratt DA. Temperature-dependence of radical-trapping activity of phenoxazine, phenothiazine and their aza-analogues clarifies the way forward for new antioxidant design. Chem Sci 2021; 12:11065-11079. [PMID: 34522304 PMCID: PMC8386644 DOI: 10.1039/d1sc02976b] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Accepted: 07/10/2021] [Indexed: 11/22/2022] Open
Abstract
The prediction and/or rationalization of diarylamine radical-trapping antioxidant (RTA) activity at the elevated temperatures where they are most useful presents a significant challenge, precluding the development of new technology. Whilst structure-activity relationships at ambient temperatures are well established, their predictive capacity at elevated temperatures is poor due to competing reactions. A striking example involves phenoxazine, which is a superior RTA relative to its sulfur analog phenothiazine at ambient temperature (e.g. k = 3.9 × 107 vs. 7.6 × 106 M-1 s-1 at 37 °C, respectively), but is demonstrably inferior at elevated temperatures. Despite being inherently less oxidizable in electrochemical experiments and high-accuracy computations, phenoxazine is more rapidly consumed than phenothiazine in autoxidations at 160 °C - a result which we attribute to a lower reorganization energy barrier to oxidation. Given these observations, we surmised that incorporation of an electronegative N-atom into the phenoxazine ring system would decrease the driving force for oxidation and 'rescue' its activity. Indeed, this was found to be the case for nitrogen incorporation at any position, regardless of the impact on the inherent RTA activity. Analogous experiments were carried out on phenothiazines into which nitrogen atoms were incorporated, revealing little benefit at 160 °C. These results suggest that for highly reactive diarylamines (i.e. those with k > 106 M-1 s-1), further enhancements in reactivity do not materially improve their ability to inhibit hydrocarbon autoxidation at elevated temperatures. Instead, their stability to one-electron oxidation determines their efficacy.
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Affiliation(s)
- Jia-Fei Poon
- Department of Chemistry and Biomolecular Sciences, University of Ottawa 10 Marie Curie Pvt. Ottawa Ontario K1N 6N5 Canada
| | - Luke A Farmer
- Department of Chemistry and Biomolecular Sciences, University of Ottawa 10 Marie Curie Pvt. Ottawa Ontario K1N 6N5 Canada
| | - Evan A Haidasz
- Department of Chemistry and Biomolecular Sciences, University of Ottawa 10 Marie Curie Pvt. Ottawa Ontario K1N 6N5 Canada
| | - Derek A Pratt
- Department of Chemistry and Biomolecular Sciences, University of Ottawa 10 Marie Curie Pvt. Ottawa Ontario K1N 6N5 Canada
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8
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Shah R, Poon JF, Haidasz EA, Pratt DA. Temperature-Dependent Effects of Alkyl Substitution on Diarylamine Antioxidant Reactivity. J Org Chem 2021; 86:6538-6550. [PMID: 33900079 DOI: 10.1021/acs.joc.1c00365] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Alkylated diphenylamines are among the most efficacious radical-trapping antioxidants (RTAs) for applications at elevated temperatures since they are able to trap multiple radical equivalents due to catalytic cycles involving persistent diphenylnitroxide and diphenylaminyl radical intermediates. We have previously shown that some heterocyclic diarylamine RTAs possess markedly greater efficacy than typical alkylated diphenylamines, and herein, report on our efforts to identify optimal alkyl substitution of the scaffold, which we had found to be the ideal compromise between reactivity and stability. Interestingly, the structure-activity relationships differ dramatically with temperature: para-alkyl substitution slightly increased reactivity and stoichiometry at 37 and 100 °C due to more favorable (stereo)electronic effects and corresponding diarylaminyl/diarylnitroxide formation, while ortho-alkyl substitution slightly decreased both reactivity and stoichiometry. No such trends were evident at 160 °C; instead, the compounds were segregated into two groups based on the presence/absence of benzylic C-H bonds. Electron spin resonance spectroscopy indicates that increased efficacy was associated with lesser diarylnitroxide formation, and deuterium-labeling suggests that this is due to abstraction of the benzylic H atom, precluding nitroxide formation. Computations predict that this reaction path is competitive with established fates of the diarylaminyl radical, thereby minimizing the formation of off-cycle products and leading to significant gains in high-temperature RTA efficacy.
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Affiliation(s)
- Ron Shah
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5
| | - Jia-Fei Poon
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5
| | - Evan A Haidasz
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5
| | - Derek A Pratt
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5
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9
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Florès O, Velic D, Mabrouk N, Bettaïeb A, Tomasoni C, Robert J, Paul C, Goze C, Roussakis C, Bodio E. Rapid Synthesis and Antiproliferative Properties of Polyazamacrocycle‐Based Bi‐ and Tetra‐Gold(I) Phosphine Dithiocarbamate Complexes. Chembiochem 2019; 20:2255-2261. [DOI: 10.1002/cbic.201900227] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Indexed: 12/26/2022]
Affiliation(s)
- Océane Florès
- CNRSUniversité Bourgogne Franche-ComtéICMUB UMR6302 9 avenue Alain Savary 21000 Dijon France
| | - Denis Velic
- Université de NantesUFR Sciences PharmaceutiquesLaboratoire IIciMed EA1155Département de Cancérologie 9 rue Bias 44035 Nantes France
| | - Nesrine Mabrouk
- EPHEPSL Research UniversityLaboratoire d'Immunologie et Immunothérapie des Cancers 60 Rue Mazarine 75006 Paris France
- Université Bourgogne Franche-ComtéLIIC, EA7269 7 Bd Jeanne d'Arc 21000 Dijon France
| | - Ali Bettaïeb
- EPHEPSL Research UniversityLaboratoire d'Immunologie et Immunothérapie des Cancers 60 Rue Mazarine 75006 Paris France
- Université Bourgogne Franche-ComtéLIIC, EA7269 7 Bd Jeanne d'Arc 21000 Dijon France
| | - Christophe Tomasoni
- Université de NantesUFR Sciences PharmaceutiquesLaboratoire IIciMed EA1155Département de Cancérologie 9 rue Bias 44035 Nantes France
| | - Jean‐Michel Robert
- Université de NantesUFR Sciences PharmaceutiquesLaboratoire IIciMed EA1155Département de Cancérologie 9 rue Bias 44035 Nantes France
| | - Catherine Paul
- EPHEPSL Research UniversityLaboratoire d'Immunologie et Immunothérapie des Cancers 60 Rue Mazarine 75006 Paris France
- Université Bourgogne Franche-ComtéLIIC, EA7269 7 Bd Jeanne d'Arc 21000 Dijon France
| | - Christine Goze
- CNRSUniversité Bourgogne Franche-ComtéICMUB UMR6302 9 avenue Alain Savary 21000 Dijon France
| | - Christos Roussakis
- Université de NantesUFR Sciences PharmaceutiquesLaboratoire IIciMed EA1155Département de Cancérologie 9 rue Bias 44035 Nantes France
| | - Ewen Bodio
- CNRSUniversité Bourgogne Franche-ComtéICMUB UMR6302 9 avenue Alain Savary 21000 Dijon France
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Qin QP, Wang ZF, Huang XL, Tan MX, Shi BB, Liang H. High in Vitro and in Vivo Tumor-Selective Novel Ruthenium(II) Complexes with 3-(2'-Benzimidazolyl)-7-fluoro-coumarin. ACS Med Chem Lett 2019; 10:936-940. [PMID: 31223451 DOI: 10.1021/acsmedchemlett.9b00098] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2019] [Accepted: 05/21/2019] [Indexed: 02/06/2023] Open
Abstract
Three novel Ru(II) complexes, namely, (RuCl2[La][DMSO]2)·H2O (Ru1), (RuCl2[Lb][DMSO]2) (Ru2), and (RuCl2[Lc][DMSO]2) (Ru3), which respectively contain 3-(2'-benzimidazolyl)coumarin (La), 3-(2'-benzimidazolyl)-7-fluoro-coumarin (Lb), and 3-(2'-benzimidazolyl)-7-methoxyl-coumarin (Lc), were first designed and characterized. Ru2 showed potent antitumor activity against NCI-H460 cells (IC50 = 0.30 ± 0.02 μM) and high selectivity between NCI-H460 cancer cells and normal HL-7702 cells. Ru2 induced NCI-H460 apoptosis via telomerase inhibition, which involved DNA damage, cell-cycle distribution, and S phase-protein down-regulation. However, Ru1 did not demonstrate such effects in NCI-H460 cells, which is undoubtedly associated with the key regulatory role of the 7-fluoro substituted group in the Lb ligand of Ru2. Ru2 exhibited considerably higher anticancer efficacy (inhibition rate [IR] = 61.3%) compared with cisplatin (IR= 25.5%) in a NCI-H460 xenograft mouse model. Thus, this coumarin Ru(II) compound is a promising Ru2-targeting telomerase anticancer agent.
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Affiliation(s)
- Qi-Pin Qin
- Guangxi Key Lab of Agricultural Resources Chemistry and Biotechnology, College of Chemistry and Food Science, Yulin Normal University, 1303 Jiaoyudong Road, Yulin 537000, PR China
| | - Zhen-Feng Wang
- Guangxi Key Lab of Agricultural Resources Chemistry and Biotechnology, College of Chemistry and Food Science, Yulin Normal University, 1303 Jiaoyudong Road, Yulin 537000, PR China
| | - Xiao-Ling Huang
- Guangxi Key Lab of Agricultural Resources Chemistry and Biotechnology, College of Chemistry and Food Science, Yulin Normal University, 1303 Jiaoyudong Road, Yulin 537000, PR China
| | - Ming-Xiong Tan
- Guangxi Key Lab of Agricultural Resources Chemistry and Biotechnology, College of Chemistry and Food Science, Yulin Normal University, 1303 Jiaoyudong Road, Yulin 537000, PR China
| | - Bei-Bei Shi
- Guangxi Key Lab of Agricultural Resources Chemistry and Biotechnology, College of Chemistry and Food Science, Yulin Normal University, 1303 Jiaoyudong Road, Yulin 537000, PR China
| | - Hong Liang
- State Key Laboratory for the Chemistry and Molecular Engineering of Medicinal Resources, School of Chemistry and Pharmacy, Guangxi Normal University, 15 Yucai Road, Guilin 541004, PR China
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11
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Chauvin JPR, Griesser M, Pratt DA. The antioxidant activity of polysulfides: it's radical! Chem Sci 2019; 10:4999-5010. [PMID: 31183049 PMCID: PMC6524666 DOI: 10.1039/c9sc00276f] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Accepted: 02/22/2019] [Indexed: 01/25/2023] Open
Abstract
Sulfurized olefins (polysulfides) containing four (or more) sulfur atoms react efficiently with peroxyl radicals by homolytic substitution, accounting for their primary antioxidant activity.
Olefin sulfurization, wherein alkenes and sulfur are heated together at high temperatures, produces branched polysulfides. Due to their anti-wear properties, they are indispensible additives to lubricants, but are also added to other petroleum-derived products as oxidation inhibitors. Polysulfides also figure prominently in the chemistry and biology of garlic and other plants of the Allium species. We previously reported that trisulfides, upon oxidation to their corresponding 1-oxides, are surprisingly effective radical-trapping antioxidants (RTAs) at ambient temperatures. Herein, we show that the homolytic substitution mechanism responsible also operates for tetrasulfides, but not trisulfides, disulfides or sulfides. Moreover, we show that this reactivity persists at elevated temperature (160 °C), enabling tetrasulfides to not only eclipse their 1-oxides as RTAs, but also hindered phenols and alkylated diphenylamines – the most common industrial antioxidant additives. The reactivity is unique to higher polysulfides (n ≥ 4), since homolytic substitution upon them at S2 yields stabilized perthiyl radicals. The persistence of perthiyl radicals also underlies the greater reactivity of polysulfides at elevated temperatures relative to their 1-oxides, since homolytic S–S bond cleavage is reversible in the former, but not in the latter. These results suggest that olefin sulfurization processes optimized for tetrasulfide production will afford materials that impart significantly better oxidation stability to hydrocarbon-based products to which polysulfides are added. Moreover, it suggests that RTA activity may contribute to the biological activity of plant-derived polysulfides.
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Affiliation(s)
- Jean-Philippe R Chauvin
- Department of Chemistry and Biomolecular Sciences , University of Ottawa , Ottawa , Ontario , Canada K1N 6N5 .
| | - Markus Griesser
- Department of Chemistry and Biomolecular Sciences , University of Ottawa , Ottawa , Ontario , Canada K1N 6N5 .
| | - Derek A Pratt
- Department of Chemistry and Biomolecular Sciences , University of Ottawa , Ottawa , Ontario , Canada K1N 6N5 .
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12
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Spreckelmeyer S, van der Zee M, Bertrand B, Bodio E, Stürup S, Casini A. Relevance of Copper and Organic Cation Transporters in the Activity and Transport Mechanisms of an Anticancer Cyclometallated Gold(III) Compound in Comparison to Cisplatin. Front Chem 2018; 6:377. [PMID: 30234099 PMCID: PMC6131305 DOI: 10.3389/fchem.2018.00377] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Accepted: 08/03/2018] [Indexed: 01/23/2023] Open
Abstract
The molecular mechanisms of toxicity and cellular transport of anticancer metallodrugs, including platinum-based agents, have not yet been fully elucidated. The aim of our study was to investigate the relevance of copper transporters (CTR1 and ATP7A/B), organic cation transporters (OCT2) and the multidrug and toxin extrusion proteins (MATE) in the intracellular accumulation of a novel organometallic cytotoxic Au(III) compound in cancer cells in comparison to cisplatin. Specifically, the synthesis and characterization of the gold complex [Au(pyb-H)(PPh2Ar)Cl]PF6 (PPh2Ar = 3-[4-(diphenylphosphino)phenyl]-7-methoxy-2H-chromen-2-one] (1), featuring a coumarin ligand endowed with “smart” fluorescence properties, have been achieved. Initially, the cytotoxic effects of both cisplatin and 1 were studied in a small panel of human cancer cells, and against a non-tumorigenic cell line in vitro. Thus, the human ovarian cancer cell line A2780 and its cisplatin resistant variant A2780cisR, were selected, being most sensitive to the treatment of the gold complex. Co-incubation of the metallodrugs with CuCl2 (a CTR1 substrate) increased the cytotoxic effects of both the Au(III) complex and cisplatin; while co-incubation with cimetidine (inhibitor of OCT2 and MATE) showed some effect only after 72 h incubation. ICP-MS (Inductively Coupled Plasma Mass Spectrometry) analysis of the cell extracts showed that co-incubation with CuCl2 increases Au and Cu accumulation in both cancer cell lines, in accordance with the enhanced antiproliferative effects. Conversely, for cisplatin, no increase in Pt content could be observed in both cell lines after co-incubation with either CuCl2 or cimetidine, excluding the involvement of CTR1, OCT2, and MATE in drug accumulation and overall anticancer effects. This result, together with the evidence for increased Cu content in A2780 cells after cisplatin co-treatment with CuCl2, suggests that copper accumulation is the reason for the observed enhanced anticancer effects in this cell line. Moreover, metal uptake studies in the same cell lines indicate that both 1 and cisplatin are not transported intracellularly by CTR1 and OCT2. Finally, preliminary fluorescence microscopy studies enabled the visualization of the sub-cellular distribution of the gold compound in A2780 cells, suggesting accumulation in specific cytosolic components/organelles.
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Affiliation(s)
- Sarah Spreckelmeyer
- Department Pharmacokinetics, Toxicology and Targeting, Groningen Research Institute of Pharmacy, University of Groningen, Groningen, Netherlands.,Medicinal Inorganic Chemistry Group, Department of Chemistry, University of British Columbia, Vancouver, BC, Canada
| | - Margot van der Zee
- Department Pharmacokinetics, Toxicology and Targeting, Groningen Research Institute of Pharmacy, University of Groningen, Groningen, Netherlands
| | - Benoît Bertrand
- Department Pharmacokinetics, Toxicology and Targeting, Groningen Research Institute of Pharmacy, University of Groningen, Groningen, Netherlands.,ICMUB UMR6302, CNRS, Université Bourgogne Franche-Comté, Dijon, France
| | - Ewen Bodio
- ICMUB UMR6302, CNRS, Université Bourgogne Franche-Comté, Dijon, France
| | - Stefan Stürup
- Department of Pharmacy, University of Copenhagen, Copenhagen, Denmark
| | - Angela Casini
- Department Pharmacokinetics, Toxicology and Targeting, Groningen Research Institute of Pharmacy, University of Groningen, Groningen, Netherlands.,School of Chemistry, Cardiff University, Cardiff, United Kingdom
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13
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Amorati R, Valgimigli L. Methods To Measure the Antioxidant Activity of Phytochemicals and Plant Extracts. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2018; 66:3324-3329. [PMID: 29557653 DOI: 10.1021/acs.jafc.8b01079] [Citation(s) in RCA: 84] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Measurement of antioxidant properties in plant-derived compounds requires appropriate methods that address the mechanism of antioxidant activity and focus on the kinetics of the reactions involving the antioxidants. Methods based on inhibited autoxidations are the most suited for chain-breaking antioxidants and for termination-enhancing antioxidants, while different specific studies are needed for preventive antioxidants. A selection of chemical testing methods is critically reviewed, highlighting their advantages and limitations and discussing their usefulness to investigate both pure molecules and raw extracts. The influence of the reaction medium on antioxidants' performance is also addressed.
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Affiliation(s)
- Riccardo Amorati
- University of Bologna , Department of Chemistry "G. Ciamician" , Via S. Giacomo 11 , 40126 Bologna , Italy
| | - Luca Valgimigli
- University of Bologna , Department of Chemistry "G. Ciamician" , Via S. Giacomo 11 , 40126 Bologna , Italy
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14
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Measuring Antioxidant Activity in Bioorganic Samples by the Differential Oxygen Uptake Apparatus: Recent Advances. J CHEM-NY 2017. [DOI: 10.1155/2017/6369358] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The measure of O2 consumption during the inhibited autoxidation of an easily oxidizable substrate is one of the most reliable and predictive methods to assess antioxidant activity, especially for structure-activity relationship studies, for food and industrial applications. The differential oxygen uptake apparatus described herein represents a powerful and cost-effective way to obtain antioxidant activity from inhibited autoxidation studies. These experiments provide the rate constant and the stoichiometry of the reaction between antioxidants and peroxyl radicals (ROO∙), which are involved in the propagation of radical damage. We show the operation principles and the utility of this instrumentation in the bioorganic laboratory, with regard to the recent advances in this field, ranging from the study of natural antioxidants in biomimetic system, to the use of substrates generating hydroperoxyl radicals, and to the evaluation of novel nanoantioxidants.
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15
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Shah R, Pratt DA. Determination of Key Hydrocarbon Autoxidation Products by Fluorescence. J Org Chem 2016; 81:6649-56. [DOI: 10.1021/acs.joc.6b01032] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Ron Shah
- Department of Chemistry and
Biomolecular Sciences University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
| | - Derek A. Pratt
- Department of Chemistry and
Biomolecular Sciences University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
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16
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Haidasz EA, Meng D, Amorati R, Baschieri A, Ingold KU, Valgimigli L, Pratt DA. Acid Is Key to the Radical-Trapping Antioxidant Activity of Nitroxides. J Am Chem Soc 2016; 138:5290-8. [DOI: 10.1021/jacs.6b00677] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Evan A. Haidasz
- Department
of Chemistry, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
| | - Derek Meng
- Department
of Chemistry, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
| | - Riccardo Amorati
- Department
of Chemistry “G. Ciamician”, University of Bologna, Bologna I-40126, Italy
| | - Andrea Baschieri
- Department
of Chemistry “G. Ciamician”, University of Bologna, Bologna I-40126, Italy
| | - Keith U. Ingold
- National Research Council of Canada, Ottawa, Ontario K1A 0R6, Canada
| | - Luca Valgimigli
- Department
of Chemistry “G. Ciamician”, University of Bologna, Bologna I-40126, Italy
| | - Derek A. Pratt
- Department
of Chemistry, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
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17
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Dondaine L, Escudero D, Ali M, Richard P, Denat F, Bettaieb A, Le Gendre P, Paul C, Jacquemin D, Goze C, Bodio E. Coumarin-Phosphine-Based Smart Probes for Tracking Biologically Relevant Metal Complexes: From Theoretical to Biological Investigations. Eur J Inorg Chem 2016. [DOI: 10.1002/ejic.201501304] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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18
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Bodio E, Le Gendre P, Denat F, Goze C. Development of Trackable Anticancer Agents Based on Metal Complexes. ADVANCES IN INORGANIC CHEMISTRY 2016. [DOI: 10.1016/bs.adioch.2015.09.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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19
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Haidasz EA, Van Kessel ATM, Pratt DA. A Continuous Visible Light Spectrophotometric Approach To Accurately Determine the Reactivity of Radical-Trapping Antioxidants. J Org Chem 2015; 81:737-44. [DOI: 10.1021/acs.joc.5b02183] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- Evan A. Haidasz
- Department of Chemistry and
Biomolecular Sciences, University of Ottawa, Ottawa, Ontario, K1N 6N5, Canada
| | - Antonius T. M. Van Kessel
- Department of Chemistry and
Biomolecular Sciences, University of Ottawa, Ottawa, Ontario, K1N 6N5, Canada
| | - Derek A. Pratt
- Department of Chemistry and
Biomolecular Sciences, University of Ottawa, Ottawa, Ontario, K1N 6N5, Canada
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20
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Li B, Zheng F, Chauvin JPR, Pratt DA. The medicinal thiosulfinates from garlic and Petiveria are not radical-trapping antioxidants in liposomes and cells, but lipophilic analogs are. Chem Sci 2015; 6:6165-6178. [PMID: 30090232 PMCID: PMC6054074 DOI: 10.1039/c5sc02270c] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Accepted: 07/27/2015] [Indexed: 01/11/2023] Open
Abstract
The radical-trapping antioxidant (RTA) activities of allicin and petivericin, thiosulfinates widely believed responsible for the medicinal properties of garlic and Petiveria, were determined in phosphatidylcholine lipid bilayers and mammalian cell culture.
The radical-trapping antioxidant (RTA) activities of allicin and petivericin, thiosulfinates widely believed responsible for the medicinal properties of garlic and Petiveria, were determined in phosphatidylcholine lipid bilayers. The results indicate that both compounds are surprisingly ineffective, in sharp contrast with previous studies in organic solution which showed that they undergo facile Cope elimination to produce sulfenic acids – potent radical-trapping agents. In an effort to understand the medium dependence of this activity, a more lipophilic (hexylated) analog of petivericin was synthesized and shown to be among the most effective RTAs known, but only in the presence of a hydrophilic thiol (e.g. N-acetylcysteine). Additional symmetric and unsymmetric thiosulfinates were synthesized to shed light on the structural features that underlie this reactivity. These studies reveal that amphiphilic thiosulfinates which undergo S-thiolation with a hydrophilic thiol to give lipophilic sulfenic acids are required, and that an activated methylene group – key to promote Cope elimination – is not. Interestingly, the added thiol was also found to regenerate the sulfenic acid following its reaction with peroxyl radicals. This activity was diminished at more acidic pH, suggesting that it occurs by electron transfer from the thiolate. Allicin, petivericin and hexylated petivericin were assayed as inhibitors of lipid peroxidation in human TF1a erythroblasts and HEK-293 kidney cells, revealing similar efficacies in the low μM range – the same range in which allicin and petivericin were found to induce cell death concomitant with, or as a result of, glutathione (GSH) depletion. In contrast, hexylated petivericin was not cytotoxic throughout the concentration range assayed, and had no effect on GSH levels. Taken together, the results in lipid bilayers and in cell culture suggest that the greater lipophilicity of hexylated petivericin enables it to partition to membranous cell compartments where it forms a lipid-soluble sulfenic acid that traps peroxyl radicals, whereas allicin and petivericin partition to the cytosol where they deplete GSH and induce cell death.
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Affiliation(s)
- Bo Li
- Department of Chemistry and Biomolecular Sciences , University of Ottawa , 10 Marie Curie Pvt. , Ottawa , Ontario , Canada . ; ; Tel: +1-613-562-5800 ext. 2119
| | - Feng Zheng
- Department of Chemistry and Biomolecular Sciences , University of Ottawa , 10 Marie Curie Pvt. , Ottawa , Ontario , Canada . ; ; Tel: +1-613-562-5800 ext. 2119
| | - Jean-Philippe R Chauvin
- Department of Chemistry and Biomolecular Sciences , University of Ottawa , 10 Marie Curie Pvt. , Ottawa , Ontario , Canada . ; ; Tel: +1-613-562-5800 ext. 2119
| | - Derek A Pratt
- Department of Chemistry and Biomolecular Sciences , University of Ottawa , 10 Marie Curie Pvt. , Ottawa , Ontario , Canada . ; ; Tel: +1-613-562-5800 ext. 2119
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Ali M, Dondaine L, Adolle A, Sampaio C, Chotard F, Richard P, Denat F, Bettaieb A, Le Gendre P, Laurens V, Goze C, Paul C, Bodio E. Anticancer Agents: Does a Phosphonium Behave Like a Gold(I) Phosphine Complex? Let a “Smart” Probe Answer! J Med Chem 2015; 58:4521-8. [DOI: 10.1021/acs.jmedchem.5b00480] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Moussa Ali
- Institut de Chimie Moléculaire de l’Université de Bourgogne, ICMUB UMR CNRS 6302, 9 Avenue Alain Savary, BP 47870, Dijon Cedex, 21078, France
| | - Lucile Dondaine
- École Pratique des Hautes Études, Paris, F-75014, France
- EA7269 EPHE-University of Burgundy, University of Burgundy, Dijon, F-21000, France
| | - Anais Adolle
- École Pratique des Hautes Études, Paris, F-75014, France
- EA7269 EPHE-University of Burgundy, University of Burgundy, Dijon, F-21000, France
| | - Carla Sampaio
- École Pratique des Hautes Études, Paris, F-75014, France
- EA7269 EPHE-University of Burgundy, University of Burgundy, Dijon, F-21000, France
| | - Florian Chotard
- Institut de Chimie Moléculaire de l’Université de Bourgogne, ICMUB UMR CNRS 6302, 9 Avenue Alain Savary, BP 47870, Dijon Cedex, 21078, France
| | - Philippe Richard
- Institut de Chimie Moléculaire de l’Université de Bourgogne, ICMUB UMR CNRS 6302, 9 Avenue Alain Savary, BP 47870, Dijon Cedex, 21078, France
| | - Franck Denat
- Institut de Chimie Moléculaire de l’Université de Bourgogne, ICMUB UMR CNRS 6302, 9 Avenue Alain Savary, BP 47870, Dijon Cedex, 21078, France
| | - Ali Bettaieb
- École Pratique des Hautes Études, Paris, F-75014, France
- EA7269 EPHE-University of Burgundy, University of Burgundy, Dijon, F-21000, France
| | - Pierre Le Gendre
- Institut de Chimie Moléculaire de l’Université de Bourgogne, ICMUB UMR CNRS 6302, 9 Avenue Alain Savary, BP 47870, Dijon Cedex, 21078, France
| | - Véronique Laurens
- École Pratique des Hautes Études, Paris, F-75014, France
- EA7269 EPHE-University of Burgundy, University of Burgundy, Dijon, F-21000, France
| | - Christine Goze
- Institut de Chimie Moléculaire de l’Université de Bourgogne, ICMUB UMR CNRS 6302, 9 Avenue Alain Savary, BP 47870, Dijon Cedex, 21078, France
| | - Catherine Paul
- École Pratique des Hautes Études, Paris, F-75014, France
- EA7269 EPHE-University of Burgundy, University of Burgundy, Dijon, F-21000, France
| | - Ewen Bodio
- Institut de Chimie Moléculaire de l’Université de Bourgogne, ICMUB UMR CNRS 6302, 9 Avenue Alain Savary, BP 47870, Dijon Cedex, 21078, France
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22
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Li B, Pratt DA. Methods for determining the efficacy of radical-trapping antioxidants. Free Radic Biol Med 2015; 82:187-202. [PMID: 25660993 DOI: 10.1016/j.freeradbiomed.2015.01.020] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Revised: 01/20/2015] [Accepted: 01/22/2015] [Indexed: 01/10/2023]
Abstract
Hydrocarbon autoxidation is the free radical chain reaction primarily responsible for the oxidative degradation of organic materials, including those that make up cells, tissues, and organs. The identification of compounds that slow this process (antioxidants) and the quantitation of their efficacies have long been goals of academic and industrial researchers. Antioxidants are generally divided into two types: preventive and radical-trapping (also commonly referred to as chain-breaking). Preventive antioxidants slow the rate of initiation of autoxidation, whereas radical-trapping antioxidants slow the rate of propagation by reacting with chain-propagating peroxyl radicals. The purpose of this review is to provide a comprehensive overview of different approaches to measure the kinetics of the reactions of radical-trapping antioxidants with peroxyl radicals, and their use to study the inhibition of hydrocarbon (lipid) autoxidation in homogeneous solution, as well as biphasic media (lipid bilayers) and cell culture. Direct and indirect approaches are presented and advantages and disadvantages of each are discussed in order to facilitate method selection for investigators seeking to address particular questions in this immensely popular field.
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Affiliation(s)
- Bo Li
- Department of Chemistry, University of Ottawa, Ottawa, Ontario, K1N 6N5, Canada
| | - Derek A Pratt
- Department of Chemistry, University of Ottawa, Ottawa, Ontario, K1N 6N5, Canada.
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23
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Valgimigli L, Pratt DA. Maximizing the reactivity of phenolic and aminic radical-trapping antioxidants: just add nitrogen! Acc Chem Res 2015; 48:966-75. [PMID: 25839082 DOI: 10.1021/acs.accounts.5b00035] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Hydrocarbon autoxidation, the archetype free radical chain reaction, challenges the longevity of both living organisms and petroleum-derived products. The most important strategy in slowing this process is via the intervention of radical-trapping antioxidants (RTAs), which are abundant in nature and included as additives to almost every petroleum-derived product as well as several other commercial products. Accordingly, a longstanding objective of many academic and industrial scientists has been the design and development of novel RTAs that can outperform natural and industrial standards, such as α-tocopherol, the most biologically active form of vitamin E, and dialkylated diphenylamines, respectively. Some time ago we recognized that attempts to maximize the reactivity of phenolic RTAs had largely failed because substitution of the phenolic ring with electron-donating groups to weaken the O-H bond and accelerate the rate of H atom transfer to radicals leads to compounds that are unstable in air. We surmised that incorporating nitrogen into the phenolic ring would render them more stable to one-electron oxidation, enabling their substitution with strong electron-donating groups. Guided by computational chemistry, we demonstrated that replacing the phenyl ring in very electron-rich phenols with either 3-pyridyl or 5-pyrimidyl rings leads to phenolic-like RTAs with good air stability and great reactivity. In fact, rate constants determined for the reactions of some compounds with peroxyl radicals were almost 2 orders of magnitude greater than those for α-tocopherol and implied that the reactions proceeded without an enthalpic barrier. Following extensive thermochemical and kinetic characterization, we took our studies of these compounds to more physiologically relevant media, such as lipid bilayers and human low density lipoproteins, where the heterocyclic analogues of vitamin E shone, displaying unparalleled abilities to inhibit lipid peroxidation and prompting their current investigation in animal models of degenerative disease. Moreover, we carried out studies of these compounds in several industrially relevant contexts and in particular demonstrated that they could be used synergistically with less reactive, less expensive, phenolic RTAs. More recently, our attention has turned to the application of these ideas to maximizing the reactivity of diarylamine RTAs that are common in additives to petroleum-derived products, such as lubricating oils, transmission and hydraulic fluids, and rubber. In doing so, we have developed the most reactive diarylamines ever reported. The 3-pyridyl- and 5-pyrimidyl-containing diarylamines are easily accessed using Pd- and/or Cu-catalyzed cross-coupling reactions, and display an ideal compromise between reactivity and stability. The most reactive compounds are characterized by rate constants for reactions with peroxyl radicals that are independent of temperature, implying that-as for the most reactive heterocyclic phenols-these reactions proceed without an enthalpic barrier. Unprecedented reactivity was also observed when hydrocarbon autoxidations were carried out at elevated temperatures, real-world conditions where diarylamines are uniquely effective because of a catalytic RTA activity that makes use of the hydrocarbon substrate as a sacrificial reductant. Our studies to date suggest that heterocyclic diarylamines have real potential to increase the longevity of petroleum-derived products in a variety of applications where diphenylamines are currently used.
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Affiliation(s)
- Luca Valgimigli
- Department of Chemistry “G.
Ciamician”, University of Bologna, 40126 Bologna, Italy
- Department of Chemistry, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
| | - Derek A. Pratt
- Department of Chemistry “G.
Ciamician”, University of Bologna, 40126 Bologna, Italy
- Department of Chemistry, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
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Shah R, Haidasz EA, Valgimigli L, Pratt DA. Unprecedented Inhibition of Hydrocarbon Autoxidation by Diarylamine Radical-Trapping Antioxidants. J Am Chem Soc 2015; 137:2440-3. [DOI: 10.1021/ja5124144] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- Ron Shah
- Department
of Chemistry, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5
| | - Evan A. Haidasz
- Department
of Chemistry, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5
| | - Luca Valgimigli
- Department
of Chemistry “G. Ciamician”, University of Bologna, Bologna I-40126, Italy
| | - Derek A. Pratt
- Department
of Chemistry, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5
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Amorati R, Valgimigli L. Advantages and limitations of common testing methods for antioxidants. Free Radic Res 2015; 49:633-49. [DOI: 10.3109/10715762.2014.996146] [Citation(s) in RCA: 273] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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26
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Haidasz EA, Shah R, Pratt DA. The Catalytic Mechanism of Diarylamine Radical-Trapping Antioxidants. J Am Chem Soc 2014; 136:16643-50. [DOI: 10.1021/ja509391u] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Evan A. Haidasz
- Department of Chemistry, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
| | - Ron Shah
- Department of Chemistry, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
| | - Derek A. Pratt
- Department of Chemistry, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
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Amorati R, Foti MC, Valgimigli L. Antioxidant activity of essential oils. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2013; 61:10835-47. [PMID: 24156356 DOI: 10.1021/jf403496k] [Citation(s) in RCA: 380] [Impact Index Per Article: 34.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Essential oils (EOs) are liquid mixtures of volatile compounds obtained from aromatic plants. Many EOs have antioxidant properties, and the use of EOs as natural antioxidants is a field of growing interest because some synthetic antioxidants such as BHA and BHT are now suspected to be potentially harmful to human health. Addition of EOs to edible products, either by direct mixing or in active packaging and edible coatings, may therefore represent a valid alternative to prevent autoxidation and prolong shelf life. The evaluation of the antioxidant performance of EOs is, however, a crucial issue, because many commonly used "tests" are inappropriate and give contradictory results that may mislead future research. The chemistry explaining EO antioxidant activity is discussed along with an analysis of the potential in food protection. Literature methods to assess EOs' antioxidant performance are critically reviewed.
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Affiliation(s)
- Riccardo Amorati
- Department of Chemistry "G. Ciamician", University of Bologna , Via S. Giacomo 11, I-40126 Bologna, Italy
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Haidasz EA, Li B, Pratt DA. Reaction mechanisms: radical and radical ion reactions. ACTA ACUST UNITED AC 2013. [DOI: 10.1039/c3oc90013d] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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