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Gamov G, Kiselev A, Zavalishin M, Yarullin D. Formation and hydrolysis of pyridoxal-5’-phosphate hydrazones and Schiff bases: Prediction of equilibrium and rate constants. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.120961] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
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Rozanov ES, Grazhdan KV, Kiselev AN, Gamov GA. Protolytic Equilibrium Constants in Aqueous Solutions of Pyridoxal-5'-Phosphate Hydrazone and L-Tyrosine. RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A 2022. [DOI: 10.1134/s0036024422040252] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Spatial structure and conformations of hydrazones derived from pyridoxal 5′-phosphate and 2-, 3-pyridinecarbohydrazide in the light of NMR study and quantum chemical calculations. J Mol Liq 2021. [DOI: 10.1016/j.molliq.2021.117372] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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Gamov G, Murekhina A, Aleksandriiskii V. Dephosphorylation of pyridoxal 5′‐phosphate‐derived Schiff bases in the presence of bovine alkaline phosphatase. INT J CHEM KINET 2021. [DOI: 10.1002/kin.21541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- George Gamov
- Research Institute of Thermodynamics and Kinetics of Chemical Processes Ivanovo State University of Chemistry and Technology Ivanovo Russia
| | - Anastasia Murekhina
- Research Institute of Thermodynamics and Kinetics of Chemical Processes Ivanovo State University of Chemistry and Technology Ivanovo Russia
| | - Viktor Aleksandriiskii
- Research Institute of Thermodynamics and Kinetics of Chemical Processes Ivanovo State University of Chemistry and Technology Ivanovo Russia
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Gamov GA, Meshkov AN, Zavalishin MN, Petrova MV, Khokhlova AY, Gashnikova AV, Sharnin VA. Binding of pyridoxal, pyridoxal 5'-phosphate and derived hydrazones to bovine serum albumin in aqueous solution. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2020; 233:118165. [PMID: 32120288 DOI: 10.1016/j.saa.2020.118165] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 02/10/2020] [Accepted: 02/16/2020] [Indexed: 06/10/2023]
Abstract
In the present paper, the kinetics of a reaction between bovine serum albumin (BSA) and pyridoxal, pyridoxal 5'-phosphate was studied, apparent rate constant of product formation and dissociation as well as binding constants were determined. Pyridoxal 5'-phosphate hydrazones of isonicotinic, picolinic, 2-furoic, thiophene-2-carboxylic, pyrazinoic acids binding to BSA was studied by spectrofluorimetry, stability constants of the associates were calculated from experimental data using maximal likelihood approach. The changes in the secondary structure of BSA induced by hydrazones addition were studied by IR spectroscopy. New freely available software for curve fitting was developed as a part of the software kit designed for the solution chemistry and used for a specific problem of this study, IR spectra processing.
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Affiliation(s)
- G A Gamov
- Research Institute of Thermodynamics and Kinetics of Chemical Processes, Ivanovo State University of Chemistry and Technology, 153000 Ivanovo, Sheremetevskii pr. 7, Russia.
| | | | - M N Zavalishin
- Research Institute of Thermodynamics and Kinetics of Chemical Processes, Ivanovo State University of Chemistry and Technology, 153000 Ivanovo, Sheremetevskii pr. 7, Russia
| | - M V Petrova
- Research Institute of Thermodynamics and Kinetics of Chemical Processes, Ivanovo State University of Chemistry and Technology, 153000 Ivanovo, Sheremetevskii pr. 7, Russia
| | - A Yu Khokhlova
- Research Institute of Thermodynamics and Kinetics of Chemical Processes, Ivanovo State University of Chemistry and Technology, 153000 Ivanovo, Sheremetevskii pr. 7, Russia
| | - A V Gashnikova
- Research Institute of Thermodynamics and Kinetics of Chemical Processes, Ivanovo State University of Chemistry and Technology, 153000 Ivanovo, Sheremetevskii pr. 7, Russia
| | - V A Sharnin
- Research Institute of Thermodynamics and Kinetics of Chemical Processes, Ivanovo State University of Chemistry and Technology, 153000 Ivanovo, Sheremetevskii pr. 7, Russia
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Gamov G, Meshkov A, Zavalishin M, Khokhlova AY, Gashnikova A, Aleksandriiskii V, Sharnin V. Protonation of hydrazones derived from pyridoxal 5′-phosphate: Thermodynamic and structural elucidation. J Mol Liq 2020. [DOI: 10.1016/j.molliq.2020.112822] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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7
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Spatial structure, thermodynamics and kinetics of formation of hydrazones derived from pyridoxal 5′-phosphate and 2-furoic, thiophene-2-carboxylic hydrazides in solution. J Mol Liq 2019. [DOI: 10.1016/j.molliq.2019.03.125] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Gamov GA, Zavalishin MN, Kabirov DN, Usacheva TR, Sharnin VA. Thermodynamics and Kinetics of the Reaction between Pyridoxal-5-Phosphate and Hydrazides of 2-Methylfuran-3-Carboxylic and Thiophene-3-Carboxylic Acids in an Aqueous Solution. RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A 2019. [DOI: 10.1134/s0036024419020110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Gamov GA, Zavalishin MN, Khokhlova AY, Gashnikova AV, Sharnin VA. Stability of Cu(II) and Zn(II) Complexes with Pyridinecarbohydrazones of Pyridoxal-5-phosphate in Aqueous Solution. RUSS J GEN CHEM+ 2018. [DOI: 10.1134/s1070363218070149] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Influence of regioisomerism on stability, formation kinetics and ascorbate oxidation preventive properties of Schiff bases derived from pyridinecarboxylic acids hydrazides and pyridoxal 5′-phosphate. J Mol Liq 2017. [DOI: 10.1016/j.molliq.2017.07.106] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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Genaro-Mattos TC, Maurício ÂQ, Rettori D, Alonso A, Hermes-Lima M. Antioxidant Activity of Caffeic Acid against Iron-Induced Free Radical Generation--A Chemical Approach. PLoS One 2015; 10:e0129963. [PMID: 26098639 PMCID: PMC4476807 DOI: 10.1371/journal.pone.0129963] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Accepted: 05/13/2015] [Indexed: 01/08/2023] Open
Abstract
Caffeic acid (CA) is a phenolic compound widely found in coffee beans with known beneficial effects in vivo. Many studies showed that CA has anti-inflammatory, anti-mutagenic, antibacterial and anti-carcinogenic properties, which could be linked to its antioxidant activity. Taking in consideration the reported in vitro antioxidant mechanism of other polyphenols, our working hypothesis was that the CA antioxidant activity could be related to its metal-chelating property. With that in mind, we sought to investigate the chemical antioxidant mechanism of CA against in vitro iron-induced oxidative damage under different assay conditions. CA was able to prevent hydroxyl radical formation promoted by the classical Fenton reaction, as determined by 2-deoxyribose (2-DR) oxidative degradation and DMPO hydroxylation. In addition to its ability to prevent hydroxyl radical formation, CA had a great inhibition of membrane lipid peroxidation. In the lipid peroxidation assays CA acted as both metal-chelator and as hydrogen donor, preventing the deleterious action promoted by lipid-derived peroxyl and alkoxyl radicals. Our results indicate that the observed antioxidant effects were mostly due to the formation of iron-CA complexes, which are able to prevent 2-DR oxidation and DMPO hydroxylation. Noteworthy, the formation of iron-CA complexes and prevention of oxidative damage was directly related to the pH of the medium, showing better antioxidant activity at higher pH values. Moreover, in the presence of lipid membranes the antioxidant potency of CA was much higher, indicating its enhanced effectiveness in a hydrophobic environment. Overall, our results show that CA acts as an antioxidant through an iron chelating mechanism, preventing the formation of free hydroxyl radicals and, therefore, inhibiting Fenton-induced oxidative damage. The chemical properties of CA described here—in association with its reported signaling effects—could be an explanation to its beneficial effects observed in vivo.
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Affiliation(s)
- Thiago C. Genaro-Mattos
- Laboratório de Radicais Livres, Departamento de Biologia Celular, Universidade de Brasília, Brasília, DF, Brazil
- Laboratório de Espectrometria de Massa, Embrapa Recursos Genéticos e Biotecnologia, Brasília, DF, Brazil
- Instituto de Química, Universidade de Brasília, Brasília, DF, Brazil
| | - Ângelo Q. Maurício
- Laboratório de Radicais Livres, Departamento de Biologia Celular, Universidade de Brasília, Brasília, DF, Brazil
| | - Daniel Rettori
- Laboratório de Química e Bioquímica de Espécies Altamente Reativas, Departamento de Ciências Exatas e da Terra, Universidade Federal de São Paulo–UNIFESP, São Paulo, SP, Brazil
| | - Antonio Alonso
- Instituto de Física, Universidade Federal de Goiás, Goiânia, GO, Brazil
| | - Marcelo Hermes-Lima
- Laboratório de Radicais Livres, Departamento de Biologia Celular, Universidade de Brasília, Brasília, DF, Brazil
- * E-mail:
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Yoon I, Park HS, Cui BC, Li JZ, Kim JH, Lkhagvadulam B, Shim YK. Photodynamic and Antioxidant Activities of Divalent Transition Metal Complexes of Methyl Pheophorbide-a. B KOREAN CHEM SOC 2011. [DOI: 10.5012/bkcs.2011.32.8.2981] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Sreeprasad TS, Samal AK, Pradeep T. Body- or tip-controlled reactivity of gold nanorods and their conversion to particles through other anisotropic structures. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:9463-71. [PMID: 17665936 DOI: 10.1021/la700851x] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
We report the shape transformation of gold nanorods to spherical nanoparticles, assisted by cupric ions. The reaction proceeds through a series of structures and could be arrested at any stage to produce particles of desired shape. In the presence of a larger concentration of cetyltrimethylammonium bromide (CTAB), selective etching of the tips of the nanorods occurs to a greater extent. The subsequent transformation is driven by the surface reconstruction of nanorods to generate more stable surfaces. As the stability of various surfaces depends on the protecting agent used, the reactivity is modified by controlling its presence at the surface. We show that the body of the rods is more susceptible for reaction at reduced CTAB concentrations. During the conversion to particles, several anisotropic transient structures were observed and were imaged using high-resolution transmission electron microscopy (HRTEM). The transformation occurs due to the hydroxyl radicals produced by Cu2+ in the presence of ascorbic acid (AA). A mechanism has been proposed and several control experiments were conducted to test it. The cupric ion induced shape transformations can be extended to other ions, and knowing the mechanism allows the control of the process to stabilize various anisotropic structures.
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Affiliation(s)
- T S Sreeprasad
- DST Unit on Nanoscience (DST-UNS), Department of Chemistry and Sophisticated Analytical Instrument Facility, Indian Institute of Technology, Madras, Chennai, India
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Charkoudian LK, Pham DM, Kwon AM, Vangeloff AD, Franz KJ. Modifications of boronic ester pro-chelators triggered by hydrogen peroxide tune reactivity to inhibit metal-promoted oxidative stress. Dalton Trans 2007:5031-42. [DOI: 10.1039/b705199a] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Endo N, Nishiyama K, Okabe M, Matsumoto M, Kanouchi H, Oka T. Vitamin B6 suppresses apoptosis of NM-1 bovine endothelial cells induced by homocysteine and copper. Biochim Biophys Acta Gen Subj 2006; 1770:571-7. [PMID: 17208380 DOI: 10.1016/j.bbagen.2006.11.009] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2006] [Revised: 11/02/2006] [Accepted: 11/14/2006] [Indexed: 11/29/2022]
Abstract
Hyperhomocysteinemia is an important risk factor for atherosclerosis. We previously reported that formation of early atherosclerosis in the rat aorta was associated with hyperhomocysteinemia and reduction of antioxidant activity caused by low concentration of vitamin B(6)in vivo. In the present study, we examined effects of vitamin B(6) on apoptosis of bovine endothelial cells (NM-1 cells) treated with homocysteine and copper. Homocysteine and copper induced extracellular hydrogen peroxide, intracellular ROS and cellular lipid peroxide levels. Cell viability was reduced to 30% compared to that of control cells. On the other hand, pyridoxal treatment as well as EDTA treatment increased viability of NM-1 cells treated with homocysteine and copper to about 60%, and significantly decreased extracellular hydrogen peroxide, intracellular ROS and cellular lipid peroxide levels. The treatment of catalase recovered cell viability and reduced the level of extracellular hydrogen peroxide and intracellular ROS. Cell death by homocysteine and copper was confirmed to be due to apoptosis by evaluation of DNA fragmentation and by TUNEL assay. However, apoptosis of NM-1 cells induced by homocysteine and copper was due to a caspase-independent pathway as it was not inhibited by the caspase inhibitor, Z-VAD-fmk. Apoptosis of NM-1 cells induced by homocysteine and copper accompanied with mitochondrial permeability but not cytochrome c release. These results suggest that pyridoxal treatment suppresses apoptosis of NM-1 cells induced by homocysteine and copper, most likely through antioxidant effects.
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Affiliation(s)
- Naoko Endo
- Department of Veterinary Medicine, Faculty of Agriculture, Kagoshima University, 1-21-24 Korimoto, Kagoshima 890-0065, Japan
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Andrade RG, Ginani JS, Lopes GKB, Dutra F, Alonso A, Hermes-Lima M. Tannic acid inhibits in vitro iron-dependent free radical formation. Biochimie 2006; 88:1287-96. [PMID: 16600466 DOI: 10.1016/j.biochi.2006.02.006] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2005] [Revised: 02/07/2006] [Accepted: 02/17/2006] [Indexed: 11/18/2022]
Abstract
The antioxidant activity of tannic acid (TA), a plant polyphenol claimed to possess antimutagenic and anticarcinogenic activities, was studied by monitoring (i) 2-deoxyribose degradation (a technique for OH detection), (ii) ascorbate oxidation, (iii) ascorbate radical formation (determined by EPR analysis) and (iv) oxygen uptake induced by the system, which comprised Fe(III) complexes (EDTA, nitrilotriacetic acid (NTA) or citrate as co-chelators), ascorbate and oxygen. TA removes Fe(III) from the co-chelators (in the case of EDTA, this removal is slower than with NTA or citrate), forming an iron-TA complex less capable of oxidizing ascorbate into ascorbate radical or mediating 2-deoxyribose degradation. The effectiveness of TA against 2-deoxyribose degradation, ascorbate oxidation and ascorbate radical formation was substantially higher in the presence of iron-NTA (or iron-citrate) than with iron-EDTA, which is consistent with the known formation constants of the iron complexes with the co-chelators. Oxygen uptake and 2-deoxyribose degradation induced by Fe(II) autoxidation were also inhibited by TA. These results indicate that TA inhibits OH formation induced by Fe(III)/ascorbate/O(2) mainly by arresting Fe(III)-induced ascorbate oxidation and Fe(II) autoxidation (which generates Fe(II) and H(2)O(2), respectively), thus limiting the production of Fenton reagents and OH formation. We also hypothesize that the Fe(II) complex with TA exhibits an OH trapping activity, which explains the effect of TA on the Fenton reaction.
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Affiliation(s)
- Roberto G Andrade
- Oxyradical Research Group, Departamento de Biologia Celular, Universidade de Brasília, Brasília, DF, 70910-900, Brazil.
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Battin EE, Perron NR, Brumaghim JL. The Central Role of Metal Coordination in Selenium Antioxidant Activity. Inorg Chem 2006; 45:499-501. [PMID: 16411681 DOI: 10.1021/ic051594f] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Oxidative DNA damage occurs in vivo by hydroxyl radical generated in metal-mediated Fenton-type reactions. Cell death and mutation caused by this DNA damage are implicated in neurodegenerative and cardiovascular diseases, cancer, and aging. Treating these conditions with antioxidants, including highly potent selenium antioxidants, is of growing interest. Gel electrophoresis was used to directly quantify DNA damage inhibition by selenium compounds with copper and H(2)O(2). Selenocystine inhibited all DNA damage at low micromolar concentrations, whereas selenomethionine showed similar inhibition at 40 times these concentrations, and 2-aminophenyl diselenide showed no effect. DNA damage inhibition by these selenium compounds does not correspond to their glutathione peroxidase activities, and UV-vis and gel electrophoresis results indicate that selenium-copper coordination is essential for DNA damage inhibition. Understanding this novel metal-coordination mechanism for selenium antioxidant activity will aid in the design of more potent antioxidants to treat and prevent diseases caused by oxidative stress.
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Affiliation(s)
- Erin E Battin
- Department of Chemistry, Clemson University, Clemson, SC 29634-0973, USA
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Andrade RG, Dalvi LT, Silva JMC, Lopes GKB, Alonso A, Hermes-Lima M. The antioxidant effect of tannic acid on the in vitro copper-mediated formation of free radicals. Arch Biochem Biophys 2005; 437:1-9. [PMID: 15820211 DOI: 10.1016/j.abb.2005.02.016] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2004] [Revised: 01/31/2005] [Indexed: 02/06/2023]
Abstract
Tannic acid (TA) has well-described antimutagenic and antioxidant activities. The antioxidant activity of TA has been previously attributed to its capacity to form a complex with iron ions, interfering with the Fenton reaction [Biochim. Biophys. Acta 1472, 1999, 142]. In this work, we observed that TA inhibits, in the micromolar range, in vitro Cu(II) plus ascorbate-mediated hydroxyl radical (*OH) formation (determined as 2-deoxyribose degradation) and oxygen uptake, as well as copper-mediated ascorbate oxidation and ascorbate radical formation (quantified in EPR studies). The effect of TA against 2-deoxyribose degradation was three orders of magnitude higher than classic *OH scavengers, but was similar to several other metal chelators. Moreover, the inhibitory effectiveness of TA, by the four techniques used herein, was inversely proportional to the Cu(II) concentration in the media. These results and the observation of copper-induced changes in the UV spectra of TA are indications that the antioxidant activity of TA relates to its copper chelating ability. Thus, copper ions complexed to TA are less capable of inducing ascorbate oxidation, inhibiting the sequence of reactions that lead to 2-deoxyribose degradation. On the other hand, the efficiency of TA against 2-deoxyribose degradation declined considerably with increasing concentrations of the *OH detector molecule, 2-deoxyribose, suggesting that the copper-TA complex also possesses an *OH trapping activity.
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Affiliation(s)
- Roberto G Andrade
- Oxyradical Research Group, Departamento de Biologia Celular, Universidade de Brasília, Brasília, DF 70910-900, Brazil
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Chaston TB, Richardson DR. Iron chelators for the treatment of iron overload disease: relationship between structure, redox activity, and toxicity. Am J Hematol 2003; 73:200-10. [PMID: 12827659 DOI: 10.1002/ajh.10348] [Citation(s) in RCA: 135] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The success of the iron (Fe) chelator desferrioxamine (DFO) in the treatment of beta-thalassemia is limited by its lack of bioavailability. The design and characterization of synthetic alternatives to DFO has attracted much scientific interest and has led to the discovery of orally active chelators that can remove pathological Fe deposits. However, chelators that access intracellular Fe pools can be toxic by either inhibiting Fe-containing enzymes or promoting Fe-mediated free radical damage. Interestingly, toxicity does not necessarily correlate with Fe-binding affinity or with chelation efficacy, suggesting that other factors may promote the cytopathic effects of chelators. In this review, we discuss the interactions of chelators and their Fe complexes with biomolecules that can lead to toxicity and tissue damage.
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Affiliation(s)
- Timothy B Chaston
- Children's Cancer Institute Australia for Medical Research, The Iron Metabolism and Chelation Program, Randwick, Sydney, New South Wales, Australia
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Maurício AQ, Lopes GKB, Gomes CS, Oliveira RG, Alonso A, Hermes-Lima M. Pyridoxal isonicotinoyl hydrazone inhibits iron-induced ascorbate oxidation and ascorbyl radical formation. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1620:15-24. [PMID: 12595068 DOI: 10.1016/s0304-4165(02)00502-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Previous work from our laboratory demonstrated that pyridoxal isonicotinoyl hydrazone (PIH) has in vitro antioxidant activity against iron plus ascorbate-induced 2-deoxyribose degradation due to its ability to chelate iron; the resulting Fe(III)-PIH(2) complex is supposedly unable to catalyze oxyradical formation. A putative step in the antioxidant action of PIH is the inhibition of Fe(III)-mediated ascorbate oxidation, which yields the Fenton reagent Fe(II) [Biochim. Biophys. Acta 1523 (2000) 154]. In this work, we demonstrate that PIH inhibits Fe(III)-EDTA-mediated ascorbate oxidation (measured at 265 nm) and the formation of ascorbyl radical (in electron paramagnetic resonance (EPR) studies). The efficiency of PIH against ascorbate oxidation, ascorbyl radical formation and 2-deoxyribose degradation was dose dependent and directly proportional to the period of preincubation of PIH with Fe(III)-EDTA. The efficiency of PIH in inhibiting ascorbate oxidation and ascorbyl radical formation was also inversely proportional to the Fe(III)-EDTA concentration in the media. When EDTA was replaced by the weaker iron ligand nitrilotriacetic acid (NTA), PIH was much more effective in preventing ascorbate oxidation, ascorbyl radical formation and 2-deoxyribose degradation. Moreover, the replacement of EDTA with citrate, a physiological chelator with a low affinity for iron, also resulted in PIH having a higher efficiency in inhibiting iron-mediated ascorbate oxidation and 2-deoxyribose degradation. These results demonstrate that PIH removes iron from EDTA (or from either NTA or citrate), forming an iron-PIH complex that cannot induce ascorbate oxidation effectively, thus inhibiting iron-mediated oxyradical formation. These results are of pharmacological relevance because PIH has been considered for experimental chelating therapy in iron-overload diseases.
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Affiliation(s)
- Angelo Q Maurício
- Oxyradical Research Group, Departamento de Biologia Celular, Universidade de Brasília, Brazil
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