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Gonzalez AL, Lozano VA, Escandar GM, Bravo MA. Determination of ochratoxin A in coffee and tea samples by coupling second-order multivariate calibration and fluorescence spectroscopy. Talanta 2020; 219:121288. [PMID: 32887030 DOI: 10.1016/j.talanta.2020.121288] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Revised: 05/02/2020] [Accepted: 05/29/2020] [Indexed: 11/19/2022]
Abstract
A new method to quantify the mycotoxin ochratoxin A (OTA) in coffee and tea samples is proposed based on second-order multivariate calibration and excitation-emission fluorescence matrix (EEFM) data. Experimental conditions were optimized by studying the effect of pH and various organized media on the fluorescence signal of OTA. For each analysed matrix (coffee grains and tea leaves), several sample pretreatments and calibration methods (external or standard addition) and data processing by chemometric models (e.g., parallel factor analysis/PARAFAC and multivariate curve resolution-alternating least squares/MCR-ALS) were evaluated and discussed. The MCR-ALS algorithm provided an adequate fit to the data for both samples, while PARAFAC was satisfactory only for the tea samples. Regarding the figures of merit, the limits of detection were in the range of 0.2-0.3 ng mL-1; furthermore, low relative prediction errors, between 2% and 4%, were achieved in both the fortified and real samples. Accordingly, the proposed methodology was applied to analyse fortified roasted and green coffee and real tea leaf samples. Satisfactory recoveries were achieved (ranging from 92 to 110%), and the obtained concentrations were in agreement with the values obtained by the reference method (based on high-performance liquid chromatography with fluorescence detection/HPLC-FLD). In addition, all samples contained OTA levels lower than the maximum permissible levels. Finally, the proposed strategy allows the use of green analytical chemistry principles; for instance, the use of organic solvents and the generation of waste products were significantly lower than for similar analytical methods reported in the literature.
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Affiliation(s)
- Albani L Gonzalez
- Laboratorio de Química Analítica y Ambiental, Instituto de Química, Facultad de Ciencias, Pontificia Universidad Católica de Valparaíso, Avenida Brasil, 2950, Valparaíso, Chile
| | - Valeria A Lozano
- Instituto de Química Rosario (CONICET-UNR), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, 2000, Rosario, Argentina
| | - Graciela M Escandar
- Instituto de Química Rosario (CONICET-UNR), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, 2000, Rosario, Argentina
| | - Manuel A Bravo
- Laboratorio de Química Analítica y Ambiental, Instituto de Química, Facultad de Ciencias, Pontificia Universidad Católica de Valparaíso, Avenida Brasil, 2950, Valparaíso, Chile.
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Tang Z, Liu X, Wang Y, Chen Q, Hammock BD, Xu Y. Nanobody-based fluorescence resonance energy transfer immunoassay for noncompetitive and simultaneous detection of ochratoxin a and ochratoxin B. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2019; 251:238-245. [PMID: 31082608 PMCID: PMC7103568 DOI: 10.1016/j.envpol.2019.04.135] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Revised: 04/26/2019] [Accepted: 04/29/2019] [Indexed: 05/21/2023]
Abstract
A noncompetitive and homogeneous fluorescence resonance energy transfer (FRET) immunoassay was developed using a nanobody (Nb) for highly sensitive and simultaneous detection of ochratoxin A (OTA) and ochratoxin B (OTB). The promoted intrinsic fluorescence (λex: 280 nm) of tryptophan residues (donor) in Nb can excite the fluorescence of OTA and OTB (acceptor) for detection (λem: 430 nm). Using optimal conditions, the limits of detection of the Nb-based FRET immunoassay were 0.06 and 0.12 ng/mL for OTA and OTB, respectively. Minimal cross reactivity was detected for several analogues of OTA and OTB as well as nonspecific proteins and antibodies. Acceptable accuracy and precision were obtained in the spike and recovery study, and the results correlated well with those by HPLC. These results demonstrated that the developed method could be a useful tool for noncompetitive, homogeneous, and simultaneous detection of OTA and OTB as well as other environmental analytes with similar fluorescence properties.
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Affiliation(s)
- Zongwen Tang
- College of Food Science and Engineering, Hainan University, 58 Renmin Avenue, Haikou, 570228, PR China
| | - Xing Liu
- College of Food Science and Engineering, Hainan University, 58 Renmin Avenue, Haikou, 570228, PR China.
| | - Yuanyuan Wang
- College of Food Science and Engineering, Hainan University, 58 Renmin Avenue, Haikou, 570228, PR China
| | - Qi Chen
- College of Food Science and Engineering, Hainan University, 58 Renmin Avenue, Haikou, 570228, PR China
| | - Bruce D Hammock
- Department of Entomology and Nematology and UCD Comprehensive Cancer Center, University of California, Davis, CA, 95616, United States
| | - Yang Xu
- State Key Laboratory of Food Science and Technology, Nanchang University, 235 Nanjing East Road, Nanchang, 330047, PR China
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Cagnasso I, Tonachini G, Berto S, Giacomino A, Mandrile L, Maranzana A, Durbiano F. Comprehensive study on the degradation of ochratoxin A in water by spectroscopic techniques and DFT calculations. RSC Adv 2019; 9:19844-19854. [PMID: 35519402 PMCID: PMC9065388 DOI: 10.1039/c9ra02086a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Accepted: 06/11/2019] [Indexed: 11/21/2022] Open
Abstract
Ochratoxin A (OTA) is one of the most important dietary risk factors and is classified as a possible carcinogen to humans. Assessing the conditions to remove it from foodstuffs in a simple and effective way is of the utmost importance. OTA behaviour in water in the pH range 1.0-12.5 was elucidated to investigate the conditions for irreversible toxicity inactivation of OTA. The results indicate that four forms, from neutral to trianionic, intervene depending on the pH. pK a1,2 were rigorously established by independent spectroscopic techniques to overcome the scarcity of literature. Then, Density Functional Theory (DFT) calculations were used to determine the most probable degradation mechanism and this was confirmed by fluorescence spectroscopy. At pH 12.5, hydrolyzation of the lactone ring starts in less than one hour, but only after two hours does the degradation process lead to fragmentation. After one week this process is not yet completed. The reaction products occurring upon re-acidification were also investigated. OTA degradation is still reversible if acidic conditions are promptly restored, yielding again a hazardous molecule. However, degradation becomes irreversible after fragmentation. This finding suggests proceeding with due caution if a base is exploited to remove the toxin.
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Affiliation(s)
- Iris Cagnasso
- Metrology for Quality of Life Division, Istituto Nazionale di Ricerca Metrologica Strada Delle Cacce 91 10135 Torino Italy
- Department of Applied Science and Technology, Politecnico di Torino Corso Duca Degli Abruzzi 24 10129 Torino Italy
| | - Glauco Tonachini
- Chemistry Department, Università di Torino Via Giuria 7 10125 Torino Italy
| | - Silvia Berto
- Chemistry Department, Università di Torino Via Giuria 7 10125 Torino Italy
| | - Agnese Giacomino
- Drug Science and Technology Department, Università di Torino Via Giuria 9 10125 Torino Italy
| | - Luisa Mandrile
- Metrology for Quality of Life Division, Istituto Nazionale di Ricerca Metrologica Strada Delle Cacce 91 10135 Torino Italy
| | - Andrea Maranzana
- Chemistry Department, Università di Torino Via Giuria 7 10125 Torino Italy
| | - Francesca Durbiano
- Metrology for Quality of Life Division, Istituto Nazionale di Ricerca Metrologica Strada Delle Cacce 91 10135 Torino Italy
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Klopčič I, Dolenc MS. Chemicals and Drugs Forming Reactive Quinone and Quinone Imine Metabolites. Chem Res Toxicol 2018; 32:1-34. [DOI: 10.1021/acs.chemrestox.8b00213] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- Ivana Klopčič
- University of Ljubljana, Faculty of Pharmacy, Aškerčeva 7, 1000 Ljubljana, Slovenia
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Samokhvalov AV, Safenkova IV, Zherdev AV, Dzantiev BB. The registration of aptamer-ligand (ochratoxin A) interactions based on ligand fluorescence changes. Biochem Biophys Res Commun 2018; 505:536-541. [PMID: 30269817 DOI: 10.1016/j.bbrc.2018.09.109] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Accepted: 09/17/2018] [Indexed: 12/12/2022]
Abstract
The fluorescent properties of ligands can change when they bind to specific receptors. Modulated by the transition of the ligand from the free to the bound state, fluorescence makes it possible both to detect this ligand and quantitatively register its binding. We characterized the interaction of ochratoxin A (OTA) with the specific G-quadruplex aptamer through excitation-emission matrix fluorescence spectroscopy. It was shown that the formation of the complex changes the OTA fluorescence spectrum both in the region of the main peak at λex/λem 380/430 nm and in the region of peak at λex/λem 265/425 nm. At pH 8.5 and OTA concentration of 30 nM, this peak is smaller in intensity than the main peak of fluorescence. The formation of the complex with the aptamer leads to an increase of the fluorescence at λex/λem 265/425 nm up to 6.5 times, which makes it up to 4.9 times more intense than fluorescence at 380/430 nm. Fluorescence of the G-quadruplex aptamer (donor) takes part in increasing of the OTA (acceptor) emission at λex/λem 265/425 nm due to the resonance energy transfer. The concentration regularities of the modulated fluorescence of OTA at λex/λem 265/425 nm have been studied. Their correspondence to the calculations of complexation conducted on the basis of the dissociation constant is shown.
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Affiliation(s)
- Alexey V Samokhvalov
- A.N. Bach Institute of Biochemistry, Research Centre of Biotechnology of the Russian Academy of Sciences, Leninsky Prospect 33, 119071, Moscow, Russia
| | - Irina V Safenkova
- A.N. Bach Institute of Biochemistry, Research Centre of Biotechnology of the Russian Academy of Sciences, Leninsky Prospect 33, 119071, Moscow, Russia
| | - Anatoly V Zherdev
- A.N. Bach Institute of Biochemistry, Research Centre of Biotechnology of the Russian Academy of Sciences, Leninsky Prospect 33, 119071, Moscow, Russia
| | - Boris B Dzantiev
- A.N. Bach Institute of Biochemistry, Research Centre of Biotechnology of the Russian Academy of Sciences, Leninsky Prospect 33, 119071, Moscow, Russia.
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Xiang Y, Camarada MB, Wen Y, Wu H, Chen J, Li M, Liao X. Simple voltammetric analyses of ochratoxin A in food samples using highly-stable and anti-fouling black phosphorene nanosensor. Electrochim Acta 2018. [DOI: 10.1016/j.electacta.2018.06.055] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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Ochratoxin A: Molecular Interactions, Mechanisms of Toxicity and Prevention at the Molecular Level. Toxins (Basel) 2016; 8:111. [PMID: 27092524 PMCID: PMC4848637 DOI: 10.3390/toxins8040111] [Citation(s) in RCA: 171] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Revised: 03/31/2016] [Accepted: 04/06/2016] [Indexed: 01/28/2023] Open
Abstract
Ochratoxin A (OTA) is a widely-spread mycotoxin all over the world causing major health risks. The focus of the present review is on the molecular and cellular interactions of OTA. In order to get better insight into the mechanism of its toxicity and on the several attempts made for prevention or attenuation of its toxic action, a detailed description is given on chemistry and toxicokinetics of this mycotoxin. The mode of action of OTA is not clearly understood yet, and seems to be very complex. Inhibition of protein synthesis and energy production, induction of oxidative stress, DNA adduct formation, as well as apoptosis/necrosis and cell cycle arrest are possibly involved in its toxic action. Since OTA binds very strongly to human and animal albumin, a major emphasis is done regarding OTA-albumin interaction. Displacement of OTA from albumin by drugs and by natural flavonoids are discussed in detail, hypothesizing their potentially beneficial effect in order to prevent or attenuate the OTA-induced toxic consequences.
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Li T, Kim BB, Ha TH, Shin YB, Kim MG. The effects of pH and surfactants on the absorption and fluorescence properties of ochratoxin A and zearalenone. LUMINESCENCE 2015; 30:1106-11. [DOI: 10.1002/bio.2866] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Accepted: 01/03/2015] [Indexed: 11/09/2022]
Affiliation(s)
- Taihua Li
- Department of School of Physics and Chemistry; Gwangju Institute of Science & Technology (GIST); 261 Cheomdan-gwagiro Gwangju 500-712 Republic of Korea
| | - Bo Bae Kim
- Biomedical Translational Research Center; Korea Research Institute of Bioscience & Biotechnology (KRIBB); 125 Gwahak-ro, Yuseong-gu Daejeon 305-806 Republic of Korea
| | - Tae Hwan Ha
- Biomedical Translational Research Center; Korea Research Institute of Bioscience & Biotechnology (KRIBB); 125 Gwahak-ro, Yuseong-gu Daejeon 305-806 Republic of Korea
| | - Yong-Beom Shin
- Biomedical Translational Research Center; Korea Research Institute of Bioscience & Biotechnology (KRIBB); 125 Gwahak-ro, Yuseong-gu Daejeon 305-806 Republic of Korea
| | - Min-Gon Kim
- Department of School of Physics and Chemistry; Gwangju Institute of Science & Technology (GIST); 261 Cheomdan-gwagiro Gwangju 500-712 Republic of Korea
- Advanced Photonics Research Institute; Gwangju Institute of Science & Technology (GIST); 261 Cheomdan-gwagiro Gwangju 500-712 Republic of Korea
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Physico-Chemical Investigation on the Interaction Between Ochratoxin A and Heptakis-2,6-di-O-Methyl-β-Cyclodextrin. J SOLUTION CHEM 2014. [DOI: 10.1007/s10953-014-0214-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Akman SA, Adams M, Case D, Park G, Manderville RA. Mutagenicity of ochratoxin A and its hydroquinone metabolite in the SupF gene of the mutation reporter plasmid Ps189. Toxins (Basel) 2012; 4:267-80. [PMID: 22606376 PMCID: PMC3347003 DOI: 10.3390/toxins4040267] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2012] [Revised: 03/29/2012] [Accepted: 04/06/2012] [Indexed: 02/02/2023] Open
Abstract
Ochratoxin A (OTA) is a mycotoxin that enhances renal tumor formation in the outer medulla of male rat kidney. Direct DNA damage and subsequent mutagenicity may contribute to these processes. In this study we have determined whether OTA in the absence or presence of activated rat liver microsomes (RLM) or redox-active transition metals (Fe(III) or Cu(II)) causes promutagenic DNA damage in the supF gene of the mutation reporter plasmid pS189 replicating in human Ad293 cells. In addition, we have assessed the mutagenicity of the hydroquinone metabolite (OTHQ) of OTA in the absence or presence of cysteine without added cofactors. Our results show that oxidation of OTA, either by RLM or by transition metal ions, activates OTA to a directly genotoxic mutagen(s). The Fe(III)/OTA system was the most potent mutagen in our experimental system, causing a 32-fold increase in mutant fraction (MF) above the spontaneous control MF. The Cu(II)/OTA system caused a 9-fold increase in MF, while a 6-10-fold increase in MF was observed for OTA in the presence of RLM. The OTHQ metabolite is also mutagenic, especially in the presence of cysteine, in which a 6-fold increase in MF was observed. Our data provide further insight into OTA bioactivation that may account for its in vivo mutagenicity in male rat kidney.
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Affiliation(s)
- Steven A. Akman
- Department of Cancer Biology, Wake Forest University Health Sciences, Winston-Salem, North Carolina, NC, USA;
| | - Marissa Adams
- Department of Cancer Biology, Wake Forest University Health Sciences, Winston-Salem, North Carolina, NC, USA;
| | - Doug Case
- Department of Public Health Sciences, Wake Forest University Health Sciences, Winston-Salem, North Carolina, NC, USA;
| | - Gyungse Park
- Department of Chemistry, College of Science and Technology, Kunsan National University, Miryong-Dong, Kusan, Korea;
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Li T, Jo EJ, Kim MG. A label-free fluorescence immunoassay system for the sensitive detection of the mycotoxin, ochratoxin A. Chem Commun (Camb) 2012; 48:2304-6. [DOI: 10.1039/c2cc17088d] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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12
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Hadjeba-Medjdoub K, Tozlovanu M, Pfohl-Leszkowicz A, Frenette C, Paugh RJ, Manderville RA. Structure-activity relationships imply different mechanisms of action for ochratoxin A-mediated cytotoxicity and genotoxicity. Chem Res Toxicol 2011; 25:181-90. [PMID: 22126095 DOI: 10.1021/tx200406c] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Ochratoxin A (OTA) is a fungal toxin that is classified as a possible human carcinogen based on sufficient evidence for carcinogenicity in animal studies. The toxin is known to promote oxidative DNA damage through production of reactive oxygen species (ROS). The toxin also generates covalent DNA adducts, and it has been difficult to separate the biological effects caused by DNA adduction from that of ROS generation. In the current study, we have derived structure-activity relationships (SAR) for the role of the C5 substituent of OTA (C5-X = Cl) by first comparing the ability of OTA, OTBr (C5-X = Br), OTB (C5-X = H), and OTHQ (C5-X = OH) to photochemically react with GSH and 2'-deoxyguanosine (dG). OTA, OTBr, and OTHQ react covalently with GSH and dG following photoirradiation, while the nonchlorinated OTB does not react photochemically with GSH and dG. These findings correlate with their ability to generate covalent DNA adducts (direct genotoxicity) in human bronchial epithelial cells (WI26) and human kidney (HK2) cells, as evidenced by the (32)P-postlabeling technique. OTB lacks direct genotoxicity, while OTA, OTBr, and OTHQ act as direct genotoxins. In contrast, their cytotoxicity in opossum kidney epithelial cells (OK) and WI26 cells did not show a correlation with photoreactivity. In OK and WI26 cells, OTA, OTBr, and OTB are cytotoxic, while the hydroquinone OTHQ failed to exhibit cytotoxicity. Overall, our data show that the C5-Cl atom of OTA is critical for direct genotoxicity but plays a lesser role in OTA-mediated cytotoxicity. These SARs suggest different mechanisms of action (MOA) for OTA genotoxicity and cytotoxicity and are consistent with recent findings showing OTA mutagenicity to stem from direct genotoxicity, while cytotoxicity is derived from oxidative DNA damage.
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Affiliation(s)
- Kheira Hadjeba-Medjdoub
- Laboratory Chemical Engineering, Department Bioprocess & Microbial System, UMR CNRS/INPT/UPS 5503 , ENSA Toulouse, France
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Pfohl-Leszkowicz A, Manderville RA. An update on direct genotoxicity as a molecular mechanism of ochratoxin a carcinogenicity. Chem Res Toxicol 2011; 25:252-62. [PMID: 22054007 DOI: 10.1021/tx200430f] [Citation(s) in RCA: 166] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Ochratoxin A (OTA) is a naturally occurring chlorophenolic fungal toxin that contaminates a wide range of food products and poses a cancer threat to humans. The mechanism of action (MOA) for OTA renal carcinogenicity is a controversial issue. In 2005, direct genotoxicity (covalent DNA adduct formation) was proposed as a MOA for OTA-mediated carcinogenicity [ Manderville , R. A. ( 2005 ) Chem. Res. Toxicol. 18 , 1091 - 1097 ]. At that time, inconsistent results had been published on OTA genotoxicity/mutagenicity, and conclusive evidence for OTA-mediated DNA adduction had been lacking. In this update, published data from the past 6-7 years are presented that provide new hypotheses for the MOA of OTA-mediated carcinogenicity. While direct genotoxicity remains a controversial issue for OTA, new findings from the Umemura and Nohmi laboratories provide definitive results for the mutagenicity of OTA in the target tissue (outer medulla) of male rat kidney that rules out oxidative DNA damage. These findings, coupled with our own efforts that provide new structural evidence for DNA adduction by OTA, has strengthened the argument for involvement of direct genotoxicity in OTA-mediated renal carcinogenesis. This MOA should be taken into consideration for OTA human risk assessment.
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Affiliation(s)
- Annie Pfohl-Leszkowicz
- Laboratoire de Génie Chimique , UMR CNRS/INPT/UPS 5503, INP/ENSA Toulouse, 1 Avenue Agrobiopole, F-31326 Auzeville-Tolosane, France.
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Li T, Jeon KS, Suh YD, Kim MG. A label-free, direct and noncompetitive FRET immunoassay for ochratoxin A based on intrinsic fluorescence of an antigen and antibody complex. Chem Commun (Camb) 2011; 47:9098-100. [DOI: 10.1039/c1cc12604k] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Hashemi J, Alizadeh N. Investigation of solvent effect and cyclodextrins on fluorescence properties of ochratoxin A. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2009; 73:121-126. [PMID: 19261540 DOI: 10.1016/j.saa.2009.02.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2008] [Revised: 01/14/2009] [Accepted: 02/03/2009] [Indexed: 05/27/2023]
Abstract
Fluorescence properties of ochratoxin A (OTA) solutions depend on the pH, solvent polarity and can be influenced by the presence of cyclodextrins (CDs). In this work, the effect of b-cyclodextrin (b-CD) and heptakis-2,6-dimethyl-o-b-cyclodextrin (ome-CD), on fluorescence properties of OTA in aqueous solutions has been investigated by means of steady-state fluorescence at different pHs (range 2-10). Binding constants of OTA/CDs inclusion complexes have been determined by applying by non-linear regression analysis. A 1:1 stoichiometry of OTA/CDs complexes has been observed at all tested pHs. The use of ome-CD generally resulted in the greatest fluorescence intensity. The effects of solvent and pH on the positions of lambdamax (excitation) and lambdamax (emission) of OTA was determined. Correlations between the excitation and emission wavelength of OTA (monoanion and dianionic forms) and the solvent parameters were analysed with Lippert-Mataga plots. Results show that the peak position is affected mainly by specific and non-specific types of interactions between the solvent and solute. The fluorescence quenching of OTA by chloroform (aprotic) and water (protic) were studied in methanol as solvent at room temperature. The quenching was found to be appreciable and a non-linear curve with downward curvature was obtained in the Stern-Volmer (SV) plot for the water in the concentration range studied. The quenching efficiency is related to hydrogen bond-donating capacity of the quencher molecule. It was inferred that non-linearity can be attributed to fractional accessibility of fluorophore to quencher. The quenching constant was calculated from the modified SV equation.
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Affiliation(s)
- Javad Hashemi
- Department of Chemistry, Faculty of Science, Tarbiat Modares University, P.O. Box 14115-175, Tehran, Iran
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Cruz-Aguado JA, Penner G. Determination of ochratoxin a with a DNA aptamer. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2008; 56:10456-61. [PMID: 18983163 DOI: 10.1021/jf801957h] [Citation(s) in RCA: 405] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
This work describes the identification of an aptamer that binds with high affinity and specificity to ochratoxin A (OTA), a mycotoxin that occurs in wheat and other foodstuffs, and a quantitative detection method for OTA based on the use of this aptamer. Aptamers are single-stranded oligonucleotides selected in vitro to bind to molecular targets. The aptamer selected in this work exhibited a dissociation constant in the nanomolar range and did not bind compounds with structures similar to OTA such as N-acetylphenylalanine or warfarin. The aptamer bound with a 100-fold less affinity to ochratoxin B. The selected aptamers could be used for the determination of ppb quantities of OTA in naturally contaminated wheat samples. Further work is ongoing to broaden the application demonstrated here with the development of sensors, affinity columns, and other analytical systems for field and laboratory determination of this toxin in food and agricultural products.
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Frenette C, Paugh RJ, Tozlovanu M, Juzio M, Pfohl-Leszkowicz A, Manderville RA. Structure–activity relationships for the fluorescence of ochratoxin A: Insight for detection of ochratoxin A metabolites. Anal Chim Acta 2008; 617:153-61. [DOI: 10.1016/j.aca.2007.12.030] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2007] [Revised: 12/17/2007] [Accepted: 12/19/2007] [Indexed: 11/24/2022]
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18
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La JQH, Michaelides AA, Manderville RA. Tautomeric equilibria in phenolic A-ring derivatives of prodigiosin natural products. J Phys Chem B 2007; 111:11803-11. [PMID: 17867672 DOI: 10.1021/jp074620z] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The prodigiosin natural products contain a common 4-methoxy-pyrromethene chromophore that is attached to a pyrrole A-ring that has its lone-pair nitrogen electrons in conjugation with the pyrromethene entity. This feature is known to play a key role in the biological activities (anticancer, antimicrobial, and immunosuppressive) of the prodigiosins. In an attempt to alter or improve upon the therapeutic potential of the prodigiosins, we have synthesized two new isomeric analogues that contain phenolic A-ring systems (a para (p)-phenol; an ortho (o)-phenol with respect to the pyrromethene) with lone-pair oxygen electrons in conjugation with the pyrromethene chromophore of the natural product. Herein, we report on the optical properties of the phenolic prodigiosin analogues that have been measured using absorbance and steady-state emission spectroscopy. For both analogues absorption measurements in aprotic solvents show that the neutral (L) ligands exist as the enol tautomers with lambda(max) ~ 460 nm, as noted for the parent prodigiosin natural product. However, in polar protic solvents the phenolic derivatives undergo ground-state prototropic tautomerization to generate keto tautomers with lambda(max) ~ 530 nm. This unique feature for a prodigiosin analogue involves proton transfer from the phenolic OH to the pyrromethene N1 proton acceptor atom. Tautomeric equilibrium constants (KT) of 1.4 in 1:4 MeCN/H2O (v/v) have been determined from examination of the absorption spectra. Titration of the o-phenolic derivative with Zn(II) in methanol yielded a 40-fold increase in fluorescence intensity (lambda(max) 542 nm) and generated a new 1:1 complex with Zn(II) with a log K of 5.29, suggesting the potential utility of this analogue to act as a fluorescence probe in a biological matrix to monitor Zn(II) concentrations. Our results demonstrate that phenolic A-ring derivatives of prodigiosins possess some unique properties that may act to enhance the biological properties of the prodigiosin natural products.
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Affiliation(s)
- Jamie Q-H La
- Department of Chemistry, University of Guelph, Guelph, Ontario, Canada
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Brow ME, Dai J, Park G, Wright MW, Gillman IG, Manderville RA. Photochemically Catalyzed Reaction of Ochratoxin A with d- and l-cysteine¶. Photochem Photobiol 2007. [DOI: 10.1562/0031-8655(2002)0760649pcrooa2.0.co2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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20
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Effect of β-cyclodextrin on spectroscopic properties of ochratoxin A in aqueous solution. J INCL PHENOM MACRO 2007. [DOI: 10.1007/s10847-006-9237-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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21
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Manderville RA. A case for the genotoxicity of ochratoxin A by bioactivation and covalent DNA adduction. Chem Res Toxicol 2006; 18:1091-7. [PMID: 16022501 DOI: 10.1021/tx050070p] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Abstract
The photophysics and photochemistry of nalidixic acid (NA) were studied as function of pH and solvent properties. The ground state of NA exhibits different protonated forms in the range of pH 1.8-10.0. Fluorescence studies showed that the same species exist at the lowest singlet excited state. Absorption experiments were carried out with NA and with the methylated analog of nalidixic acid (MNE) in different organic solvents and water pH 3, where the main species corresponds to that protonated at the carboxylic group. These studies and the DFT calculation of torsional potential energy profiles suggest that the most stable conformation of the NA in nonprotic solvents corresponds to a closed structure caused by the existence of intramolecular hydrogen bond. Absorption and fluorescence spectra were studied in sulfuric acid solution. The pK value (Ho -1.0) found in these conditions was attributed to the protonation of the 4' keto oxygen atom of the heterocyclic ring. Theoretical calculations (DFT/B3LYP/6-311G*) of the energies of the different monoprotonated forms of the NA and Fukui indexes (f(x)-) showed that the species with the proton attached to 4' keto oxygen atom is the most stable of all the cationic forms. MNE and enoxacin also showed the protonation of the 4' keto oxygen atom with similar pK values. The photodecomposition of NA is dependent on the medium properties. Faster decomposition rates were obtained in strong acid solution. In nonprotic solvents, a very slow decomposition rate was observed.
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Affiliation(s)
- Paulina Pavez
- Facultad de Química y Biología, Universidad de Santiago de Chile, Santiago, Chile
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Cigić IK, Strlič M, Schreiber A, Kocjančič M, Pihlar B. Ochratoxin A in Wine: Its Determination and Photostability. ANAL LETT 2006. [DOI: 10.1080/00032710600669424] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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24
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El-Gogary S, Grabner G. Ultraviolet photoionization of the photosensitizers khellin and visnagin in aqueous solution and in micelles: one-photon ionization is a minor process. Photochem Photobiol Sci 2006; 5:311-6. [PMID: 16520866 DOI: 10.1039/b515615g] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
One-photon ionization, leading to formation of hydrated electrons and radical cations, has been proposed as a possible mechanism of action of some sensitizers in photobiology. In this contribution, we have investigated this proposal for the compounds khellin and visnagin, used in photomedical applications. Nanosecond transient absorption spectroscopy covering a wide range of laser pulse energies was employed to measure the formation of radical cations and hydrated electrons in aqueous solution and in cationic (CTAB) as well as anionic (SDS) micellar solutions. A model allowing for simultaneous one- and two-photon processes and fully accounting for the nonlinearity of the pulse energy dependence was used to simulate the data. The results did not support the hypothesis of a significant role of one-photon ionization, the upper limits of the quantum yields of radical cation formation being phi < 0.01 for visnagin and phi < 0.004 for khellin.
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Affiliation(s)
- Sameh El-Gogary
- Department of Chemistry, Faculty of Science, Mansoura University, New Damietta, Egypt
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25
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Dai J, Park G, Perry JL, Il'ichev YV, Bow DAJ, Pritchard JB, Faucet V, Pfohl-Leszkowicz A, Manderville RA, Simon JD. Molecular aspects of the transport and toxicity of ochratoxin a. Acc Chem Res 2004; 37:874-81. [PMID: 15612677 DOI: 10.1021/ar0302134] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Ochratoxins are a class of naturally occurring compounds produced by several fungi. The most toxic is ochratoxin A (OTA), and occurrence of some human nephropathies and tumors correlate with enhanced OTA exposure. In this Account, the following areas are examined: molecular details of the binding of OTA to human serum albumin (HSA), the influences of binding to HSA on the trans-port of OTA across epithelial cell membranes by organic anion transport proteins, the oxidative activation of OTA, and the formation of OTA adducts with biological molecules. These studies are beginning to provide a detailed chemical model for the trans-port, accumulation, and genotoxic and carcinogenic effects of OTA.
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Affiliation(s)
- Jian Dai
- Department of Chemistry, Wake Forest University, Winston-Salem, North Carolina 27106, USA
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27
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Faucet V, Pfohl-Leszkowicz A, Dai J, Castegnaro M, Manderville RA. Evidence for Covalent DNA Adduction by Ochratoxin A following Chronic Exposure to Rat and Subacute Exposure to Pig. Chem Res Toxicol 2004; 17:1289-96. [PMID: 15377164 DOI: 10.1021/tx049877s] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Ochratoxin A (OTA) is a nephrotoxic mycotoxin that is a potent renal carcinogen in male rats and is suspected of being the etiological agent of Balkan endemic nephropathy (BEN) and its associated urinary tract cancers. Conflicting results have been obtained regarding the genotoxicity of OTA and its ability to react directly with DNA upon oxidative bioactivation to yield covalent DNA adducts. To characterize DNA adduction by OTA, the present study utilizes the photooxidative properties of the toxin to generate authentic C8 OTA-3'-monophosphate-deoxyguanosine (3'-dGMP) adducts for use as cochromatographic standards for (32)P-postlabeling detection of OTA-mediated DNA adduction in the kidney of rat and pig. Our results show evidence for the photooxidation of OTA to yield carbon (C)- and oxygen (O)-bonded C8-3'-dGMP adducts (C-C8 and O-C8) that have been isolated and characterized by LC/MS with in-line UV and electrospray negative ionization (ES(-)) detection. A comparison to previously published work on related C8-dG adducts supports C8 attachment by OTA. The C-C8 OTA-3'-dGMP adduct standard is shown by (32)P-postlabeling to comigrate with the major lesion detected in the kidney of rat following chronic exposure to OTA and with one of four adducts detected in the kidney of pig following subacute exposure to the toxin. The O-C8 OTA-3'-dGMP adduct standard is also shown to coelute with a lesion detected in rat kidney. These findings suggest a role for the OTA phenoxyl radical in OTA-mediated DNA adduction in vivo, provide a rationale for the tumorigenesis of OTA, and strengthen the OTA hypothesis in the etiology of BEN and the associated urinary tract tumors.
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Affiliation(s)
- Virginie Faucet
- Department Toxicology & Food Safety, Lab. Genie Chimique, Ecole Nationale Supérieure Agronomique de Toulouse, UMR-CNRS 5503, Agrobiopole-BP 107, F31326 Castanet, Tolosan Cedex, France
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28
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Perry JL, Il'ichev YV, Kempf VR, McClendon J, Park G, Manderville RA, Rüker F, Dockal M, Simon JD. Binding of Ochratoxin A Derivatives to Human Serum Albumin. J Phys Chem B 2003. [DOI: 10.1021/jp034284w] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jennifer L. Perry
- Department of Chemistry, Duke University, Durham, North Carolina 27708; Department of Chemistry, Wake Forest University, Winston-Salem, North Carolina 27109; Institute of Applied Microbiology, BOKU University of Natural Resources and Applied Life Sciences, Muthgasse 18, A-1190 Vienna, Austria; and Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710
| | - Yuri V. Il'ichev
- Department of Chemistry, Duke University, Durham, North Carolina 27708; Department of Chemistry, Wake Forest University, Winston-Salem, North Carolina 27109; Institute of Applied Microbiology, BOKU University of Natural Resources and Applied Life Sciences, Muthgasse 18, A-1190 Vienna, Austria; and Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710
| | - Valerie R. Kempf
- Department of Chemistry, Duke University, Durham, North Carolina 27708; Department of Chemistry, Wake Forest University, Winston-Salem, North Carolina 27109; Institute of Applied Microbiology, BOKU University of Natural Resources and Applied Life Sciences, Muthgasse 18, A-1190 Vienna, Austria; and Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710
| | - Jamal McClendon
- Department of Chemistry, Duke University, Durham, North Carolina 27708; Department of Chemistry, Wake Forest University, Winston-Salem, North Carolina 27109; Institute of Applied Microbiology, BOKU University of Natural Resources and Applied Life Sciences, Muthgasse 18, A-1190 Vienna, Austria; and Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710
| | - Gyungse Park
- Department of Chemistry, Duke University, Durham, North Carolina 27708; Department of Chemistry, Wake Forest University, Winston-Salem, North Carolina 27109; Institute of Applied Microbiology, BOKU University of Natural Resources and Applied Life Sciences, Muthgasse 18, A-1190 Vienna, Austria; and Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710
| | - Richard A. Manderville
- Department of Chemistry, Duke University, Durham, North Carolina 27708; Department of Chemistry, Wake Forest University, Winston-Salem, North Carolina 27109; Institute of Applied Microbiology, BOKU University of Natural Resources and Applied Life Sciences, Muthgasse 18, A-1190 Vienna, Austria; and Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710
| | - Florian Rüker
- Department of Chemistry, Duke University, Durham, North Carolina 27708; Department of Chemistry, Wake Forest University, Winston-Salem, North Carolina 27109; Institute of Applied Microbiology, BOKU University of Natural Resources and Applied Life Sciences, Muthgasse 18, A-1190 Vienna, Austria; and Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710
| | - Michael Dockal
- Department of Chemistry, Duke University, Durham, North Carolina 27708; Department of Chemistry, Wake Forest University, Winston-Salem, North Carolina 27109; Institute of Applied Microbiology, BOKU University of Natural Resources and Applied Life Sciences, Muthgasse 18, A-1190 Vienna, Austria; and Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710
| | - John D. Simon
- Department of Chemistry, Duke University, Durham, North Carolina 27708; Department of Chemistry, Wake Forest University, Winston-Salem, North Carolina 27109; Institute of Applied Microbiology, BOKU University of Natural Resources and Applied Life Sciences, Muthgasse 18, A-1190 Vienna, Austria; and Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710
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Manderville RA, Wade Calcutt M, Dai J, Park G, Gillman IG, Noftle RE, Mohammed AK, Birincioglu M, Dizdaroglu M, Rodriguez H, Akman SA. Stoichiometric preference in copper-promoted oxidative DNA damage by ochratoxin A. J Inorg Biochem 2003; 95:87-96. [PMID: 12763652 DOI: 10.1016/s0162-0134(03)00104-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The ability of the fungal carcinogen, ochratoxin A (OTA, 1), to facilitate copper-promoted oxidative DNA damage has been assessed using supercoiled plasmid DNA (Form I)-agarose gel electrophoresis and gas chromatography-mass spectrometry with selected-ion monitoring (GC-MS-SIM). OTA is shown to promote oxidative cleavage of Form I DNA with optimal cleavage efficiency occurring under excess Cu(II) conditions. As the concentration of OTA was increased and present in excess of Cu(II) the cleavage was less effective. Parallel findings were found for the ability of the OTA-Cu mixture to facilitate oxidative base damage. Yields (lesions per 10(6) DNA bases) of modified bases upon exposure of calf-thymus DNA (CT-DNA) to OTA-H(2)O(2)-Cu(II) were diminished when the OTA:Cu ratio was increased to 5:1. Electrochemical studies carried out in methanol implicate a ligand-centered 2e oxidation of OTA in the presence of excess Cu(II), while product analyses utilizing electrospray mass spectrometry support the intermediacy of the quinone, OTQ (3), in Cu-promoted oxidation of OTA. The implications of these findings with regard to the mutagenicity of OTA are discussed.
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Brow ME, Dai J, Park G, Wright MW, Gillman IG, Manderville RA. Photochemically catalyzed reaction of ochratoxin A with D- and L-cysteine. Photochem Photobiol 2002; 76:649-56. [PMID: 12511045 DOI: 10.1562/0031-8655(2002)076<0649:pcrooa>2.0.co;2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The photolysis (>300 nm) of ochratoxin A (OTA, N-[[(3R)-5-chloro-8-hydroxy-3-methyl-1-oxo-7-isochromanyl]carbonyl]-3-phenyl-L-alanine, 1) in the presence of excess (2 and 12 molar equiv) cysteine (CySH) has been investigated and found to yield sulfur adducts 5 and 6 that are characterized by liquid chromatography-mass spectrometry and 1H-NMR spectroscopy. The adduct 5 was ascribed to the Michael addition conjugate resulting from covalent attachment of CySH to the ochratoxin quinone (4) generated by photooxidation of OTA. This species was also formed by photolysis of a synthetic sample of the hydroquinone of OTA (ochratoxin hydroquinone, 3) in the presence of 12 equiv L-CySH. The conjugate 5 derived from photolysis of 3 with L-CySH was used for 1H-NMR analysis. The sulfur adduct 6 was the major species detected from covalent attachment of CySH to photoactivated OTA, and it resulted from direct displacement of the OTA Cl atom by CySH. The implications of the cysteinyl adducts to the in vivo toxicity of OTA are discussed, with particular emphasis given to conjugate 5, as products from the photooxidative pathway may be of relevance to the nephrotoxic properties of OTA.
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Affiliation(s)
- Mark E Brow
- Department of Chemistry, Wake Forest University, Winston-Salem, NC 27109-7486, USA
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