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Larin ACR, Pfrunder MC, Mullen KM, Wiedbrauk S, Boase NR, Fairfull-Smith KE. Synergistic or antagonistic antioxidant combinations - a case study exploring flavonoid-nitroxide hybrids. Org Biomol Chem 2023; 21:1780-1792. [PMID: 36728689 DOI: 10.1039/d2ob02101c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Neurodegenerative diseases impose a considerable medical and public health burden on populations throughout the world. Oxidative stress, an imbalance in pro-oxidant/antioxidant homeostasis that leads to the generation of reactive oxygen species (ROS), has been implicated in the progression of a number of neurodegenerative diseases. The manipulation of ROS levels may represent a promising treatment option to slow down neurodegeneration, although adequate potency of treatments has not yet been achieved. Using a hybrid pharmacology approach, free radical nitroxide antioxidants were hybridised with a class of natural antioxidants, flavonoids, to form a potential multitargeted antioxidant. Modification of the Baker-Venkataraman reaction achieved the flavonoid-nitroxide hybrids (6-9) in modest yields. Antioxidant evaluation of the hybrids by cyclic voltammetry showed both redox functionalities were still active, with little influence on oxidation potential. Assessment of the peroxyl radical scavenging ability through an ORAC assay showed reduced antioxidant activity of the hybrids compared to their individual components. It was hypothesized that the presence of the phenol in the hybrids creates a more acidic medium which does not favour regeneration of the nitroxide from the corresponding oxammonium cation, disturbing the typical catalytic cycle of peroxyl radical scavenging by nitroxides. This work highlights the potential intricacies involved with drug hybridization as a strategy for new therapeutic development.
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Affiliation(s)
- Astrid C R Larin
- School of Chemistry and Physics, Faculty of Science, Queensland University of Technology, Brisbane, Queensland, 4001, Australia.,Centre for Materials Science, Queensland University of Technology, Brisbane, Queensland, 4001, Australia.
| | - Michael C Pfrunder
- School of Chemistry and Physics, Faculty of Science, Queensland University of Technology, Brisbane, Queensland, 4001, Australia.,Centre for Materials Science, Queensland University of Technology, Brisbane, Queensland, 4001, Australia.
| | - Kathleen M Mullen
- School of Chemistry and Physics, Faculty of Science, Queensland University of Technology, Brisbane, Queensland, 4001, Australia.,Centre for Materials Science, Queensland University of Technology, Brisbane, Queensland, 4001, Australia.
| | - Sandra Wiedbrauk
- School of Chemistry and Physics, Faculty of Science, Queensland University of Technology, Brisbane, Queensland, 4001, Australia.,Centre for Materials Science, Queensland University of Technology, Brisbane, Queensland, 4001, Australia.
| | - Nathan R Boase
- School of Chemistry and Physics, Faculty of Science, Queensland University of Technology, Brisbane, Queensland, 4001, Australia.,Centre for Materials Science, Queensland University of Technology, Brisbane, Queensland, 4001, Australia.
| | - Kathryn E Fairfull-Smith
- School of Chemistry and Physics, Faculty of Science, Queensland University of Technology, Brisbane, Queensland, 4001, Australia.,Centre for Materials Science, Queensland University of Technology, Brisbane, Queensland, 4001, Australia.
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Lugo-González JC, Gómez-Tagle P, Flores-Alamo M, Yatsimirsky AK. Mechanistic study of carboxylic acid and phosphate ester cleavage by oximate metal complexes surpassing the limiting reactivity of highly basic free oximate anions. Dalton Trans 2020; 49:2452-2467. [PMID: 31994558 DOI: 10.1039/c9dt04733f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Two tridentate and one tetradentate new ligands containing the terminal oxime group separated from secondary amino and pyridine groups as additional binding sites by two or three methylene groups have been prepared. Their acid-base properties, as well as the composition and stability of their complexes with Zn(ii) and Cd(ii) ions, were determined by potentiometric and spectrophotometric titrations. The X-ray structure of a Cd(ii) complex of a related tridentate oxime ligand previously studied in solution was determined. All oximate complexes show high reactivity in the cleavage of aryl acetates, paraoxon, parathion and 4-nitrophenyl diphenyl phosphate, with rate constants significantly surpassing the limiting rate constants observed for highly basic free oximate anions. The second-order rate constants for individual oximate complexes in solution are assigned to each ligand, metal cation and substrate. The results of the cleavage of 4-substituted phenyl acetates were analyzed in terms of Brønsted correlations with the leaving group pKa, which demonstrated a change in the rate determining step from the nucleophilic attack to the leaving group departure upon an increase in the leaving group basicity. The zero slope of the Brønsted correlation for the nucleophilic attack indicates transition state stabilization through electrophilic assistance by the metal ion. This interpretation is supported by metal selectivity in the relative efficiency of the cleavage of paraoxon and parathion. The existence of the alpha-effect in ester cleavage by coordinated oximates is confirmed by an analysis of the Brønsted correlations with the nucleophile basicity for metal bound oximate and alkoxo or hydroxo nucleophiles. The very high reactivity of the oximate complexes of the new ligands is attributed to transition state stabilization and to the removal of the solvational imbalance of oximate anions that impedes the expected increase in the reactivity of highly basic free anions.
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Affiliation(s)
| | - Paola Gómez-Tagle
- Universidad Nacional Autónoma de México, Facultad de Química, 04510, Mexico City, Mexico.
| | - Marcos Flores-Alamo
- Universidad Nacional Autónoma de México, Facultad de Química, 04510, Mexico City, Mexico.
| | - Anatoly K Yatsimirsky
- Universidad Nacional Autónoma de México, Facultad de Química, 04510, Mexico City, Mexico.
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Zhou N, Feng T, Shen X, Cui J, Wu R, Wang L, Wang S, Zhang S, Chen H. Synthesis, characterization, and radioprotective activity of α,β-unsaturated aryl sulfone analogs and their Tempol conjugates. MEDCHEMCOMM 2017; 8:1063-1068. [PMID: 30108819 DOI: 10.1039/c7md00017k] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Accepted: 03/02/2017] [Indexed: 12/19/2022]
Abstract
Some novel α,β-unsaturated aromatic sulfone analogs (5a-5m) and their Tempol conjugates (6a-6e) have been synthetically prepared, characterized and evaluated for their radioprotective activity under γ-ray radiation. The Tempol conjugates were characterized by X-ray single crystal diffraction. In vitro studies showed that 5a, 5b and 6b had superior activities to Ex-Rad pre-treated before 5 Gy irradiation, and 5a, 6a and 6b had better activities than Ex-Rad after 5 Gy irradiation, while 5a, 6a and 6b exhibited both prophylactic and mitigation effects, indicating the advantage of combining α,β-unsaturated aromatic sulfones with Tempol nitroxide. Both p53 and phospho-p53 levels were significantly lower in compound-treated cells than those in untreated irradiated cells. The conjugates offer an improved radioprotective ability, which is an advantage in the treatment protocol.
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Affiliation(s)
- Nan Zhou
- Department of Medicinal Chemistry , School of Pharmacy , Fourth Military Medical University , Xi'an 710032 , Shaanxi , China . ;
| | - Tian Feng
- Department of Medicinal Chemistry , School of Pharmacy , Fourth Military Medical University , Xi'an 710032 , Shaanxi , China . ;
| | - Xin Shen
- Department of Medicinal Chemistry , School of Pharmacy , Fourth Military Medical University , Xi'an 710032 , Shaanxi , China . ;
| | - Jiahui Cui
- Department of Medicinal Chemistry , School of Pharmacy , Fourth Military Medical University , Xi'an 710032 , Shaanxi , China . ;
| | - Rangxin Wu
- Department of Medicinal Chemistry , School of Pharmacy , Fourth Military Medical University , Xi'an 710032 , Shaanxi , China . ;
| | - Libin Wang
- Department of Medicinal Chemistry , School of Pharmacy , Fourth Military Medical University , Xi'an 710032 , Shaanxi , China . ;
| | - Siwang Wang
- Department of Medicinal Chemistry , School of Pharmacy , Fourth Military Medical University , Xi'an 710032 , Shaanxi , China . ;
| | - Shengyong Zhang
- Department of Medicinal Chemistry , School of Pharmacy , Fourth Military Medical University , Xi'an 710032 , Shaanxi , China . ;
| | - Hui Chen
- Department of Medicinal Chemistry , School of Pharmacy , Fourth Military Medical University , Xi'an 710032 , Shaanxi , China . ;
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Lugo-González JC, Gómez-Tagle P, Huang X, M Del Campo J, Yatsimirsky AK. Substrate Specificity and Leaving Group Effect in Ester Cleavage by Metal Complexes of an Oximate Nucleophile. Inorg Chem 2017; 56:2060-2069. [PMID: 28170234 DOI: 10.1021/acs.inorgchem.6b02739] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Deprotonated zinc(II) and cadmium(II) complexes of a tridentate oxime nucleophile (1, OxH) show a very high reactivity, breaking by 2-3 orders of magnitude the previously established limiting reactivity of oximate nucleophiles in the cleavage of substituted phenyl acetates and phosphate triesters, but are unreactive with p-nitrophenyl phosphate di- and monoesters. With reactive substrates, these complexes operate as true catalysts through an acylation-deacylation mechanism. Detailed speciation and kinetic studies in a wide pH interval allowed us to establish as catalytically active forms [Cd(Ox)]+, [Zn(Ox)(OH)], and [Zn(Ox)(OH)2]- complexes. The formation of an unusual and most reactive zinc(II) oximatodihydroxo complex was confirmed by electrospray ionization mass spectrometry data and supported by density functional theory calculations, which also supported the previously noticed fact that the coordinated water in [Zn(OxH)(H2O)2]2+ deprotonates before the oxime. Analysis of the leaving group effect on the cleavage of phenyl acetates shows that the rate-determining step in the reaction with the free oximate anion is the nucleophilic attack, while with both zinc(II) and cadmium(II) oximate complexes, it changes to the expulsion of the leaving phenolate anion. The major new features of these complexes are (1) a very high esterolytic activity surpassing that of enzyme hydrolysis of aryl acetate esters and (2) an increased reactivity of coordinated oxime compared to free oxime in phosphate triester cleavage, contrary to the previously observed inhibitory effect of oxime coordination with these substrates.
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Affiliation(s)
| | - Paola Gómez-Tagle
- Facultad de Química, Universidad Nacional Autónoma de México , 04510 Mexico City, México
| | - Xiaomin Huang
- Facultad de Química, Universidad Nacional Autónoma de México , 04510 Mexico City, México
| | - Jorge M Del Campo
- Facultad de Química, Universidad Nacional Autónoma de México , 04510 Mexico City, México
| | - Anatoly K Yatsimirsky
- Facultad de Química, Universidad Nacional Autónoma de México , 04510 Mexico City, México
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Design, synthesis, and biological evaluation of novel Tempol derivatives as effective antitumor agents. RESEARCH ON CHEMICAL INTERMEDIATES 2016. [DOI: 10.1007/s11164-016-2560-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Acharya S, Bhat NN, Sanjeev G, Narayana Y. Evaluation of micronuclei induced by energetic electrons delivered at different dose rates per pulse. J Radioanal Nucl Chem 2014. [DOI: 10.1007/s10967-014-3388-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Nairy RK, Bhat NN, Anjaria KB, Sreedevi B, Sapra BK, Narayana Y. Study of gamma radiation induced damages and variation of oxygen enhancement ratio with radiation dose using Saccharomyces cerevisiae. J Radioanal Nucl Chem 2014. [DOI: 10.1007/s10967-014-3408-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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