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Shiuhjen Jiang - One of the best experts on this subject based on the ideXlab platform.
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determination of Selenium Compounds in food supplements using reversed phase liquid chromatography inductively coupled plasma mass spectrometry
Microchemical Journal, 2013Co-Authors: Yujhe Hsieh, Shiuhjen JiangAbstract:Abstract A reversed phase HPLC–ICP-MS method for the speciation of Selenium Compounds is described. Chromatographic separation was performed in a gradient elution mode using 2 mmol L − 1 sodium 1-pentanesulfonate and 5 mmol L − 1 citric acid in 3% methanol (pH 2.70) and 5 mmol L − 1 NaH 2 PO 4 and 5 mmol L − 1 citric acid in 3% methanol (pH 2.77). The potentially interfering 38 Ar 40 Ar + and 40 Ar 40 Ar + at Selenium masses of m / z 78 and 80 were reduced in intensity significantly by using 1.0 mL min − 1 CH 4 as a reactive cell gas in the dynamic reaction cell. Calibration curves were linear in the range 0.1–10 μg L − 1 . The detection limits of the procedure were in the range of 0.04–0.07 μg Se L − 1 . This method has been applied to determine various Selenium Compounds in NIST SRM 1567a Wheat Flour and food supplements purchased locally. The accuracy of the method has been verified by comparing the sum of the concentration of individual species obtained by the present procedure with the total concentration of the element. The Selenium Compounds were quantitatively extracted with a mixture of Protease XIV and mobile phase solution in a microwave field at 37 °C during a period of 30 min. The extraction efficiency was better than 91%. The spike recoveries were in the range of 92–104% for all determinations. The electrospray ionization-mass spectrometer has been tested to identify the unknown Selenium Compounds detected in the food supplements. γ-glutamyl-methyl-Se-cysteine was identified in one brand of the Selenium Tablet.
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Determination of Selenium Compounds in food supplements using reversed-phase liquid chromatography–inductively coupled plasma mass spectrometry
Microchemical Journal, 2013Co-Authors: Yujhe Hsieh, Shiuhjen JiangAbstract:Abstract A reversed phase HPLC–ICP-MS method for the speciation of Selenium Compounds is described. Chromatographic separation was performed in a gradient elution mode using 2 mmol L − 1 sodium 1-pentanesulfonate and 5 mmol L − 1 citric acid in 3% methanol (pH 2.70) and 5 mmol L − 1 NaH 2 PO 4 and 5 mmol L − 1 citric acid in 3% methanol (pH 2.77). The potentially interfering 38 Ar 40 Ar + and 40 Ar 40 Ar + at Selenium masses of m / z 78 and 80 were reduced in intensity significantly by using 1.0 mL min − 1 CH 4 as a reactive cell gas in the dynamic reaction cell. Calibration curves were linear in the range 0.1–10 μg L − 1 . The detection limits of the procedure were in the range of 0.04–0.07 μg Se L − 1 . This method has been applied to determine various Selenium Compounds in NIST SRM 1567a Wheat Flour and food supplements purchased locally. The accuracy of the method has been verified by comparing the sum of the concentration of individual species obtained by the present procedure with the total concentration of the element. The Selenium Compounds were quantitatively extracted with a mixture of Protease XIV and mobile phase solution in a microwave field at 37 °C during a period of 30 min. The extraction efficiency was better than 91%. The spike recoveries were in the range of 92–104% for all determinations. The electrospray ionization-mass spectrometer has been tested to identify the unknown Selenium Compounds detected in the food supplements. γ-glutamyl-methyl-Se-cysteine was identified in one brand of the Selenium Tablet.
A Hartwig - One of the best experts on this subject based on the ideXlab platform.
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interaction of Selenium Compounds with zinc finger proteins involved in dna repair
FEBS Journal, 2004Co-Authors: Holger Blessing, Silke Kraus, Philipp Heindl, A HartwigAbstract:As an essential element, Selenium is present in enzymes from several families, including glutathione peroxidases, and is thought to exert anticarcinogenic properties. A remarkable feature of Selenium consists of its ability to oxidize thiols under reducing conditions. Thus, one mode of action recently suggested is the oxidation of thiol groups of metallothionein, thereby providing zinc for essential reactions. However, tetrahedral zinc ion complexation to four thiolates, similar to that found in metallothionein, is present in one of the major classes of transcription factors and other so-called zinc finger proteins. Within this study we investigated the effect of Selenium Compounds on the activity of the formamidopyrimidine-DNA glycosylase (Fpg), a zinc finger protein involved in base excision repair, and on the DNAbinding capacity and integrity of xeroderma pigmentosum group A protein (XPA), a zinc finger protein essential for nucleotide excision repair. The reducible Selenium Compounds phenylseleninic acid, phenylselenyl chloride, selenocystine, ebselen, and 2-nitrophenylselenocyanate caused a concentration-dependent decrease of Fpg activity, while no inhibition was detected with fully reduced selenomethionine, methylselenocysteine or some sulfurcontaining analogs. Furthermore, reducible Selenium Compounds interfered with XPA–DNA binding and released zinc from the zinc finger motif, XPAzf. Zinc release was even evident at high glutathione/oxidised glutathine ratios prevailing under cellular conditions. Finally, comparative studies with metallothionein and XPAzf revealed similar or even accelerated zinc release from XPAzf. Altogether, the results indicate that zinc finger motifs are highly reactive towards oxidizing Selenium Compounds. This could affect gene expression, DNA repair and, thus, genomic stability.
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modulation of dna repair processes by arsenic and Selenium Compounds
Toxicology, 2003Co-Authors: A Hartwig, Holger Blessing, Tanja Schwerdtle, Ingo WalterAbstract:Nickel, cadmium, cobalt and arsenic Compounds are well known carcinogens to humans and experimental animals. In addition to the induction of mainly oxidative DNA damage, they interfere with nucleotide and base excision repair (BER) at low, non-cytotoxic concentrations. In case of arsenic, an inactivation of DNA repair has also been observed for the trivalent and pentavalent methylated metabolites, with the strongest effects exerted by MMA(III) and DMA(III). As potential molecular targets, interactions with so-called zinc finger proteins involved in DNA repair and/or DNA damage signaling have been identified. For example, arsenite suppresses poly(ADP-ribosyl)ation at extremely low, environmentally relevant concentrations. Also, Fpg and XPA involved in BER and NER, respectively, are inactivated by arsenite, MMA(III) and DMA(III). Nevertheless, an interaction with the zinc finger structures of DNA repair proteins may also occur by essential trace elements such as certain Selenium Compounds, which appear to exert anticarcinogenic properties at low concentrations but may compromise genetic stability at higher concentrations.
Mikael Bjornstedt - One of the best experts on this subject based on the ideXlab platform.
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Therapeutic Potential of Selenium Compounds in the Treatment of Cancer
Molecular and Integrative Toxicology, 2018Co-Authors: Arun Kumar Selvam, Mikael Bjornstedt, Sougat MisraAbstract:The potential applications of different Selenium Compounds as cancer chemotherapeutic agents is an active area of research within the field of cancer drug discovery. The antineoplastic efficacies of many of these small molecules have been extensively investigated, mainly in multiple preclinical models of cancer. Sodium selenite and Se-methylselenocysteine represent two of such Selenium Compounds, the cytotoxic and antiproliferative efficacies of which are discussed herein. These Compounds differ in their mechanisms of action. Sodium selenite exerts its cytotoxic effects by directly oxidizing cellular free thiol pools. In contrast, Se-methylselenocysteine undergoes enzymatic transformation into methylselenol which is cytotoxic due to its ability to redox cycle with cellular thiols. Despite the inherent differences in their metabolic transformations, the disruption of the cellular redox balance and the activation of pro-death intracellular signaling pathways have been implicated as the most prevalent mechanisms of their cytotoxic effects. Both of these Selenium Compounds exert synergistic toxic effects with certain cancer chemotherapeutics. Together, the well-documented tumor-specific cytotoxic and antiproliferative effects of these Compounds have paved the path for their clinical translation. In a phase I clinical trial, it has been shown that sodium selenite is well tolerated in human up to a dose of 10.2 mg/m2 when administered daily for 5 days a week for 2 weeks. Similarly, Se-methylselenocysteine exhibits a favorable pharmacokinetic and safety profile during prolonged oral administration in healthy subjects. Further studies are warranted to investigate their cancer chemotherapeutic efficacies in clinical settings.
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redox active Selenium Compounds from toxicity and cell death to cancer treatment
Nutrients, 2015Co-Authors: Sougat Misra, Julian E. Spallholz, Mallory Boylan, Arun Kumar Selvam, Mikael BjornstedtAbstract:Selenium is generally known as an antioxidant due to its presence in selenoproteins as selenocysteine, but it is also toxic. The toxic effects of Selenium are, however, strictly concentration and chemical species dependent. One class of Selenium Compounds is a potent inhibitor of cell growth with remarkable tumor specificity. These redox active Compounds are pro-oxidative and highly cytotoxic to tumor cells and are promising candidates to be used in chemotherapy against cancer. Herein we elaborate upon the major forms of dietary Selenium Compounds, their metabolic pathways, and their antioxidant and pro-oxidant potentials with emphasis on cytotoxic mechanisms. Relative cytotoxicity of inorganic selenite and organic selenocystine Compounds to different cancer cells are presented as evidence to our perspective. Furthermore, new novel classes of Selenium Compounds specifically designed to target tumor cells are presented and the potential of Selenium in modern oncology is extensively discussed.
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Selenium Compounds are substrates for glutaredoxins a novel pathway for Selenium metabolism and a potential mechanism for Selenium mediated cytotoxicity
Biochemical Journal, 2010Co-Authors: Marita Wallenberg, Mikael Bjornstedt, Christina Hebert, Aristi P FernandesAbstract:The Grx (glutaredoxin) proteins are oxidoreductases with a central function in maintaining the redox balance within the cell. In the present study, we have explored the reactions between Selenium Compounds and the glutaredoxin system. Selenite, GS-Se-SG (selenodiglutathione) and selenocystine were all shown to be substrates of human Grx1, implying a novel role for the glutaredoxins in Selenium metabolism. During the past few years, Selenium has further evolved as a potential therapeutic agent in cancer treatment, and a leading mechanism of cytotoxicity is the generation of ROS (reactive oxygen species). Both selenite and GS-Se-SG were reduced by Grx1 and Grx2 in a non-stoichiometric manner due to redox cycling with oxygen, which in turn generated ROS. The role of Grx in Selenium toxicity was therefore explored. Cells were treated with the Selenium Compounds in combination with transient overexpression of, or small interfering RNA against, Grx1. The results demonstrated an increased viability of the cells during silencing of Grx1, indicating that Grx1 is contributing to Selenium toxicity. This is in contrast with TrxR (thioredoxin reductase), which previously was shown to protect cells from Selenium cytotoxicity, verifying a diverse role between Grx and TrxR in Selenium-mediated cytotoxicity. Furthermore, Selenium treatment led to a marked increase in protein glutathionylation and cysteinylation that potentially can influence the activity and function of several proteins within the cell.
Peter C Uden - One of the best experts on this subject based on the ideXlab platform.
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high performance liquid chromatography of Selenium Compounds utilizing perfluorinated carboxylic acid ion pairing agents and inductively coupled plasma and electrospray ionization mass spectrometric detection
Journal of Chromatography A, 2000Co-Authors: Mihaly Kotrebai, Eric Block, Julian F Tyson, Peter C UdenAbstract:Increasing speciation demands in clinical chemistry, toxicology and nutrition have made the determination of the total elements in a sample inadequate; the amount of an element and the chemical forms in which it is present need to be known. Inductively coupled plasma mass spectrometry (ICP-MS) was used after high-performance liquid chromatographic (HPLC) separation, as was electrospray ionization mass spectrometry (ESI-MS). The effect of variation of the number of carbon atoms in perfluorinated carboxylic acids used as ion-pairing agents for the separation of Selenium Compounds was examined. Trifluoroacetic acid (0.1%), pentafluoropropanoic acid (0.1%) or heptafluorobutanoic acid (0.1%; HFBA) were alternatively used as additives to methanol–water (1:99, v/v) solutions as mobile phases. Reversed-phase HPLC–ICP-MS with 0.1% HFBA in the mobile phase allowed more than 20 Selenium Compounds to be separated in 70 min in an isocratic elution mode; the separation of natural Selenium-enriched sample extracts was examined and explained. The pH of the 0.1% HFBA solution was modified with hydrochloric acid or ammonia and the pH of the sample extracts before injection was modified in order to overcome unwanted double peak formation in the chromatograms of sample extracts. Oxidations of standard γ-glutamyl-Se-methylselenocysteine and Se-methylselenocysteine were carried out using 30% H2O2 solution and identifications of Selenium-containing oxidation products were made using HPLC–ICP-MS and HPLC–ESI-MS. The principal organic oxidation product in both cases was methaneseleninic acid (MeSeO2H).
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identification of the principal Selenium Compounds in Selenium enriched natural sample extracts by ion pair liquid chromatography with inductively coupled plasma and electrospray ionization mass spectrometric detection
Analytical Communications, 1999Co-Authors: Mihaly Kotrebai, Peter C Uden, Julian F Tyson, Marc Birringer, Eric BlockAbstract:Selenium-enriched garlic and yeast sample extracts and digests were analyzed using ion-pair high performance liquid chromatography (HPLC) with on-line inductively coupled plasma-mass spectrometric (ICP-MS) and electrospray ionization-mass spectrometric (ESI-MS) detection. The principal Selenium Compounds in these samples were identified as selenomethionine, and Se-adenosyl-selenohomocysteine in yeast, and γ-glutamyl-Se-methyl-selenocysteine and possibly γ-glutamyl-selenomethionine in garlic. The Compounds identified account for 85 and 90% of the total Selenium content of the yeast and the garlic samples, respectively. On-line HPLC-ESI-MS selected ion chromatograms (SIC) and mass spectra of Selenium Compounds extracted from Selenium enriched samples are presented. Limits of quantification (LOQ, defined as S/N = 10) for HPLC-ICP-MS were in the range 10–50 ng mL–1 Se in the injected extracts. LOQ values for HPLC-ESI-MS were ca. 100 times higher than those of HPLC-ICP-MS.
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high performance liquid chromatography of selenoamino acids and organo Selenium Compounds speciation by inductively coupled plasma mass spectrometry
Journal of Chromatography A, 1997Co-Authors: Susan Mary Bird, Honghong Ge, Peter C Uden, Julian F Tyson, Eric Block, Eric DenoyerAbstract:As part of an ongoing study to identify Selenium Compounds with cancer chemopreventive activity, extracts of Selenium-enriched samples were analyzed by HPLC-inductively coupled plasma (ICP)-MS. Ion-exchange, ion pair and derivatization methods for reversed-phase HPLC were considered and advantages and disadvantages for each compared. Anion exchange allows separation of selenite and selenate, but otherwise provides poor separation. Pre-column derivatization and reversed-phase chromatography provides separation of Compounds with terminal amine functionalities, but many other species elute in the void volume. The ion pair method gave optimal separation and was compatible with standard ICP-MS operating conditions.
Kurt J. Irgolic - One of the best experts on this subject based on the ideXlab platform.
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Retention Behavior of Inorganic and Organic Selenium Compounds on a Polymer-Based Cation Exchange Column
Phosphorus Sulfur and Silicon and The Related Elements, 1998Co-Authors: Tadesse Wondimu, Mulat Abegaz, Gary Banuelos, Walter Goessler, Kurt J. IrgolicAbstract:The retention behavior of selenous acid, selenic acid, selenomethionine, selenoethionine, selenocystine, selenohomocystine, trimethyl-selenonium iodide, and (3-amino-3-carboxy-1-propyl)-dimethylselenonium iodide was studied on the polymer-based PRP-X200 cation exchange column with an aqueous solution of pyridine (20 to 100 mM) in the pH range 1.1-6.0 adjusted with formic acid as the mobile phase. An inductively coupled plasma mass spectrometer equipped with a hydraulic high pressure nebulizer served as Selenium specific detector. The retention behavior was rationalized in terms of the pH-dependent deprotonation of the Selenium Compounds and of the pyridinium cation and of the formation of ion-pairs between hydrogen selenite, selenate, or the zwitterionic groups of the selenoamino acids with the pyridinium cation. A good separation of seven Selenium Compounds was achieved within 5.0 min at 40°C with 20 mM pyridine (pH 3.70). Selenoethionine eluted 15 min after injection. Peak areas and peak heights of the ...
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Behaviour of Selenium Compounds in FI-HG-AAS
Analytical Communications, 1998Co-Authors: Amit Chatterjee, Kurt J. IrgolicAbstract:The borohydride active volatile compound formation potential of twelve Selenium Compounds [selenous acid, selenic acid, selenocystine (Secys), selenohomocystine (Sehcys), selenomethionine (Semet), selenoethionine (Seet), trimethylselenonium iodide (TmSe), selenocystathionine (Secystha), selenocystamine (Secysta), selenourea (Seur), selenocholine (Sech), and dimethyl(3-amino-3- carboxy-1-propyl)selenonium iodide (DmpSe)] were investigated in a FI-HG system with different sodium borohydride concentrations (0.3% in 0.1% sodium hydroxide, and 0.5, 0.7, and 1.0% in 0.2% sodium hydroxide) in the presence of 3 M hydrochloric acid using an atomic absorption spectrometer as Selenium-specific detector. Percentage recoveries with respect to selenous acid of selenic acid, Secys, Sehcys, Semet, Seet, TmSe, Secystha; Secysta, Seur, Sech, and DmpSe were 0, 10.3, 19.7, 23.5, 32.4, 13.7, 16.5, 16.5, 11.3, 5.6 and 7.7%, respectively in the presence of 0.3% borohydride stabilized with 0.1% sodium hydroxide. By multiplying the borohydride concentrations, percentage recoveries of TmSe, DmpSe, Sech, Sehcys and Secysta were elevated, whereas those of Semet, Seet and Seur were reduced. However, percentage recoveries of Secys and Secystha remained almost uniform within the entire borohydride range. TmSe exhibited a 105% recovery with respect to selenous acid at 1.0% borohydride concentration, whereas selenic acid was inert to borohydride active volatile compound formation.
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Retention behavior of inorganic and organic Selenium Compounds on a silica-based strong-cation-exchange column with an inductively coupled plasma mass spectrometer as Selenium-specific detector
Journal of Chromatography A, 1997Co-Authors: Walter Goessler, Mulat Abegaz, Claudia Schlagenhaufen, Kurt Kalcher, Doris Kuehnelt, Kurt J. IrgolicAbstract:Abstract The retention behavior of eight Selenium Compounds (selenous acid, selenic acid, selenocystine, selenohomocystine, selenomethionine, selenoethionine, trimethylselenonium iodide, and dimethyl(3-amino-3-carboxy-1-propyl)selenonium iodide) with aqueous solutions of pyridine (20 mmol/l) in the pH range 2.0–5.7 on a Supelcosil LC-SCX cation-exchange column was investigated. An inductively coupled plasma mass spectrometer was employed as the Selenium-specific detector. To increase the nebulization efficiency, the Meinhard concentric glass nebulizer was replaced by a hydraulic high-pressure nebulizer. At pH 5.0, seven Selenium Compounds could be separated within 400 s, but selenohomocystine and selenomethionine had the same retention time. Selenomethionine can be separated from selenohomocystine with an aqueous solution of pyridine (20 mmol/l) adjusted with formic acid to pH 2.0. At 1 ng Se ml−1, the relative standard deviations (n=5) of the signal area for the eight Selenium Compounds ranged from 7 to 11%, and at 50 ng Se ml−1 from 0.6 to 2.6%.
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Identification and quantification of inorganic and organic Selenium Compounds with highperformance liquid chromatography
Applied Organometallic Chemistry, 1993Co-Authors: Gottfried Kölbl, Kurt J. Irgolic, Kurt Kalcher, Robert J. MageeAbstract:Selenium appears in the natural Selenium cycle in the form of several organic and inorganic Compounds. The biologically beneficial and deterimental effects of ‘Selenium’ must be ascribed to particular Selenium Compounds. The identification and quantification of Selenium Compounds in biological and environmental samples is required for an understanding of the role of Selenium. The high-performance liquid-chromatographic (HPLC) methods for the separation, identification and quantification of selenite, selenate, hydrogen selenide, methaneselenol, bis(organothio) selenides, trimethylselenonium salts, selenonamino-acids, Selenium derivatives of carbohydrates, selenoproteins, selenonucleosides and other miscellaneous Selenium Compounds are summarized (193 references) and pertinent detection modes discussed. Advantages and disadvantages of the methods are pointed out. The literature is covered since 1974, the year of the first publication in this field.