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Results for “Ferrous Compounds”

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PubMed1996

The iron(II)/reductant (DH2)-induced activation of dioxygen for the demethylation of N-methylanilines: reaction mimic for the cytochrome P-450/reductase system.

Several iron(II) complexes [FeIIL+; FeII(DPAH)2 (DPAH2 = 2,6-dicarboxyl pyridine), FeII(PA)2 (PAH = picolinic acid) and FeII(bpy)2(2+)(bpy = 2,2'-bipyridine)] in combination with a reductant [DH2; PhNHNHPh (mimic of dihydroflavin)] catalytically activate O2 (1 atm) for the demethylation of N-methylanilines [PhN(CH3)2, PhNH(CH3)]. This chemistry, which appears to involve a Fenton-like intermediate [LxFeIVOOH(DH) (1c)], mimics that of the cytochrome P-450 monooxygenase/reductase proteins.

Aniline Compounds↗

PubMed2004

Plasma lipid hydroperoxides measurement by an automated xylenol orange method.

Lipid hydroperoxides (LH) appear to be good candidates as initial biomarkers of oxidative stress. We describe an automated method to quantify it, based on a known principle: oxidation of Fe II to Fe III by lipid hydroperoxides, under acidic conditions, followed by complexation of Fe III by xylenol orange. This method requires only a 10-microl sample volume of heparinized plasma or serum. It has been carried out automatically, with two reagents, in a two-end-point mode with bichromatic detection at 570 and 700 nm. The within-run precision, measured on a low- and a high-level plasma, was 5.0+/-0.3 and 14.0+/-0.6 microM (n=25 for each series). The between-run precision (one run for 18 days), evaluated on two commercial controls, was 5.6+/-0.5 microM (CV=8.9%) and 7.9+/-0.5 microM (CV=6.3%). The recovery of known amounts of tert-butylhydroperoxide (1 and 2 microM) added to human plasma was 98%. The specificity was demonstrated by the excellent correlation of the values of 42 samples measured either directly, with a simple dilution, or after gel permeation chromatography. The reference interval determined on 21 subjects was 4.9+/-1.7 microM. This was in the upper range of previously published values but our recovery and chromatographic experiments strongly suggest that former methods have underestimated the true content of LH in human plasma.

Ferric Compounds↗

PubMed2004

Properties of a novel periplasmic catalase-peroxidase from Escherichia coli O157:H7.

A subset of catalase-peroxidases are distinguished by their periplasmic location and their expression by pathogens. Kinetic and spectral properties have not been reported for any of these enzymes. We report the cloning, expression, isolation, and characterization of KatP, a periplasmic catalase-peroxidase from Escherichia coli O157:H7. Absorption spectra indicated a mixture of heme states dominated by the pentacoordinate and hexacoordinate high-spin forms. Apparent k(cat) values for catalase (1.8x10(4) s(-1)) and peroxidase (77 s(-1)) activities were greater than those of other catalase-peroxidases. However, apparent K(M) values for H2O2 were also higher (27 mM for catalase and 3 mM for peroxidase). Ferric KatP reacted with peracetic acid to form compound I (8.8x10(3) M(-1) s(-1)) and with CN(-) to form a ferri-cyano complex (3.9x10(5) M(-1) s(-1)) consistent with other catalase-peroxidases. The isolation and characterization of KatP opens new avenues to explore mechanisms by which the periplasmic catalase-peroxidases may contribute to bacterial virulence.

Bacterial Proteins↗

PubMed2005

Antioxidative protection in hypertensive patients treated with diuretics.

BACKGROUND: Recently results of the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT) showed that a thiazide diuretic was unsurpassed by any other drug class studied in achieving the level of cardiovascular protection, a finding reflected in the recent Seventh Report of the Joint National Committee on prevention, detection, evaluation, and treatment of high blood pressure (JNC7) recommendations. Oxidative stress has been found to be one of the key players in the pathophysiology of cardiovascular disease at large. The objective of this study was to check the hypothesis that diuretics may favorably affect the oxidative status of plasma, which could account in part for the results of recent trials. METHODS: In addition to the routine workup in a series of 39 medically treated hypertensive patients, we analyzed the level of antioxidative protection afforded by the ferric-reducing ability of plasma (FRAP), according to class of drug used. RESULTS: We found that patients taking diuretics had significantly better antioxidative protection expressed by the higher levels of FRAP. Although the limited number of patients did not allow us to exclude the influence of other variables in the multiple regression analysis, we did not observe any differences in the level of FRAP when the group was divided according to the other drug classes, gender (men versus women), smoking, diabetes mellitus, duration of treatment, concomitant therapy, or level of uric acid. CONCLUSIONS: The use of thiazide diuretics seems to be associated with better antioxidative protection. This observation may add to the explanation of the results of recent trials in hypertension.

Adrenergic beta-Antagonists↗

PubMed2004

Electrochemical investigation into the redox activity of Fe(II)/Fe(III) in the presence of nicotine and possible relations to neurodegenerative diseases.

The biological relevance of Fe(II)/Fe(III) is becoming evermore apparent, especially in relation to its potential role in the progression of neurodegenerative diseases such as Parkinson's and Alzheimer's disease. The reported relationship between smoking and a reduced incidence of neurodegenerative disorders prompted this work. In order to investigate whether nicotine can interact with iron, we have studied the electrochemical behaviour of a Fe(II)/Fe(III) redox couple in the presence of nicotine. Solubility issues and lack of available nonreacting salts of nicotine necessitated studies being conducted at low pH values. Cyclic voltammetry experiments revealed a definite alteration in the electrochemical behaviour of the Fe(II)/Fe(III) redox couple suggesting the capability of nicotine to complex with free iron and, hence, reduce its reactivity. This is evident from a slower rate of heterogeneous electron transfer, ks, and a shift from reversible to quasi-reversible behaviour, as characterised from the diffusion coefficient (D), the full width half maximum (FWHM), DeltaEp and Ef. Additional complexation titrations, pH ranging from 1 to 7, confirm a weak complexation reaction occurring between Fe(III) and nicotine.

Electrochemistry↗

PubMed2005

Hemoglobin I from Lucina pectinata: a model for distal heme-ligand control.

Lucina pectinata hemoglobin I (HbI), which is a ferric sulfide-reactive hemeprotein, contains a distal pocket characterized by the presence of GlnE7 and PheB10. To elucidate the structural-functional properties of HbI, oxygen binding kinetics and FTIR studies with recombinant HbI (rHbI) and a set of mutants were conducted using CO and CN- as sensors of the hemeprotein environment. Three nuCO modes were observed for rHbI at 1936 cm(-1) (A3, closed conformer) 1950 cm(-1) (A1,2, closed conformer) and 1960 cm(-1) (A0, open conformer). These nuCO were affected by substitution of GlnE7 and PheB10 in the CO complexes. The contribution of GlnE7 is demonstrated when this residue is replaced with Asn, Val or His. For instance, decreasing the positive electrostatic environment with GlnE7Val, causes an increase of 65% in the population of A0 and the disappearance and 55% reduction of the population of the A1,2 and A3 respectively. The contribution of PheB10 to the stabilization of ligands is also observed in the Leu and Tyr mutants. The PheB10Leu mutation produced an 8% decrease in the population of the A3 conformer while that of the A1,2 configuration increased by 30%. This suggests that GlnE7 and PheB10 contribute to the A3 conformer stabilizing the CO in a closed configuration. With CN- as probe no substantial differences in the nuCN was observed upon substitution of GlnE7 by Val while a slight down shift in the nuCN from 2120 cm(-1) to 2117 cm(-1) was observed in the PheB10Leu mutant. This implies that in HbICN GlnE7 moves away from the binding site while PheB10 remains in the vicinity of the bound CN-. Here, a mechanism in which the flexibility of the distal protein matrix coupled with hemeporphyrin movement toward a different configuration is suggested as an important process in the H2S transport and delivery in hemoglobin I.

Amino Acid Sequence↗

PubMed2004

Vital roles of an interhelical insertion in catalase-peroxidase bifunctionality.

The loop connecting the F and G helices of catalase-peroxidases contains a approximately 35 amino acid structure (the FG insertion) that is absent from monofunctional peroxidases. These two groups of enzymes share highly similar active sites, yet the monofunctional peroxidases lack appreciable catalase activity. Thus, the FG insertion may serve a role in catalase-peroxidase bifunctionality, despite its peripheral location relative to the active site. We produced a variant of Escherichia coli catalase-peroxidase (KatG) lacking its FG insertion (KatG(DeltaFG)). Absorption spectra indicated the heme environment of KatG(DeltaFG) was highly similar to wild-type KatG, but the variant retained only 0.2% catalase activity. In contrast, the deletion reduced peroxidase activity by only 50%. Kinetic parameters for the peroxidase and residual catalase activities of KatG(DeltaFG) as well as pH dependence studies suggested that the FG insertion supports hydrogen-bonded networks critical for reactions involving H2O2. The structure also appears to regulate access of electron donors to the active site.

Benzothiazoles↗

PubMed2006

Electrocatalytic properties of guanine, adenine, guanosine-5'-monophosphate, and ssDNA by Fe(II) bis(2,2':6',2''-terpyridine), Fe(II) tris(1,10-phenanthroline), and poly-Fe(II) tris(5-amino-1,10-phenanthroline).

The electrocatalytic oxidations of guanine, adenine, guanosine-5'-monophosphate(GMP) and ssDNA were performed in the presence of Fe(II) bis(2,2':6',2''-terpyridine) and Fe(II) tris(1,10-phenanthroline) complexes as homogeneous catalysts by cyclic voltammetric methods. The Fe(II/III) redox couple of these compounds is responsible for their catalytic properties. The electrocatalytic oxidation current of above substrates were developed from the anodic peak currents of Fe(II) bis(2,2':6',2''-terpyridine) and Fe(II) tris(1,10-phenanthroline) complexes at about +0.93 V and 0.97 V, respectively. The electrocatalytic oxidative properties of guanine by Fe(II) bis(2,2':6',2''-terpyridine) complex was measured by amperometry method using the rotating disk electrodes. Electropolymerization of Fe(II) tris(5-amino-1,10-phenanthroline) complex produced thin polymer films on gold and glassy carbon electrodes. The electrochemical quartz crystal microbalance (EQCM) and cyclic voltammetry were used to study the in situ growth of the polymer. The poly(FeII(5-NH(2)-1,10-phen)(3)) exhibited a good electrocatalytic oxidation towards guanine and also for the mixture of guanine and adenine too.

Adenine↗

PubMed2004

A comparative study of the effects of chloride, sulfate and nitrate ions on the rates of decomposition of H2O2 and organic compounds by Fe(II)/H2O2 and Fe(III)/H2O2.

The effects of chloride, nitrate, perchlorate and sulfate ions on the rates of the decomposition of hydrogen peroxide and the oxidation of organic compounds by the Fenton's process have been investigated. Experiments were conducted in a batch reactor, in the dark at pH < or = 3.0 and at 25 degrees C. Data obtained from Fe(II)/H2O2 experiments with [Fe(II)]0/[H2O2]0 > or = 2 mol mol(-1), showed that the rates of reaction between Fe(II) and H2O2 followed the order SO4(2-) > ClO4(-) = NO3- = Cl-. For the Fe(III)/H2O2 process, identical rates were obtained in the presence of nitrate and perchlorate, whereas the presence of sulfate or chloride markedly decreased the rates of decomposition of H2O2 by Fe(III) and the rates of oxidation of atrazine ([atrazine]0 = 0.83 microM), 4-nitrophenol ([4-NP]0 = 1 mM) and acetic acid ([acetic acid]0 = 2 mM). These inhibitory effects have been attributed to a decrease of the rate of generation of hydroxyl radicals resulting from the formation of Fe(III) complexes and the formation of less reactive (SO4(*-)) or much less reactive (Cl2(*-)) inorganic radicals.

Acetic Acid↗

PubMed2005

Enhanced chemical oxidation of aromatic hydrocarbons in soil systems.

Fenton's destruction of benzene, toluene, ethylbenzene, and xylene (BTEX) was investigated in soil slurry batch reactors. The purpose of the investigation was to quantify the enhancement of oxidation rates and efficiency by varying process conditions such as iron catalyst (Fe(II) or Fe(III); 2, 5, and 10mM), hydrogen peroxide (H2O2; 30, 150, 300 mM), and metal chelating agents (l-ascorbic acid, gallic acid, or N-(2-hydroxyethyl)iminodiacetic acid). Rapid contaminant mass destruction (97% after 3h) occurred in the presence of 300 mM H2O2 and 10 mM Fe(III). An enhanced removal rate (>90% removal after 15 min and 95% removal after 3h) was also observed by combining Fe(III), N-(2-hydroxyethyl)iminodiacetic acid and 300 mM H2O2. The observed BTEX mass removal rate constants (3.6-7.8 x 10(-4)s(-1)) were compared to the estimated rate constants (4.1-10.1 x 10(-3)s(-1)). The influence of non-specific oxidants loss (by reaction with iron hydroxides and soil organic matter) was also explored.

Ascorbic Acid↗

PubMed2006

Study on the pyrolysis of polyethylene in the presence of iron and copper chlorides.

Pyrolysis experiments were conducted to elucidate the effects of metal chlorides on the thermal degradation of low-density polyethylene on a continuous pyrolysis temperature range of 600 degrees C to 1100 degrees C. The present work focusses on the ratio of aromatics generated on increasing the pyrolysis temperature in the presence of metal salts, iron(II), iron(III) and copper(II) chlorides. It was observed that beside alpha,omega-dienes, alpha-olefins and n-alkanes which are usually observed during the thermal decomposition of polyethylene, the level of aromatics noticeably increases with the addition of metal salts. At high temperatures, the formation of these aromatics took place in such a way that they become the major products when polyethylene is pyrolyzed in presence of FeCl(3) and CuCl(2). Quantification of the effect of metal salts has been tempted comparing the variation of the ratio of aromatics with pyrolysis temperatures. Mechanisms responsible for the formation of these aromatics in presence of metal salts have been tentatively investigated. They are proposed to result from cyclization/dehydrogenation reactions similar to those observed during the thermal decomposition of polyethylene, but with an increased efficiency due to the metal salts.

Chlorides↗

PubMed2004

On-column complexation capillary electrophoretic separation of Fe2+ and Fe3+ using 2,6-pyridinedicarboxylic acid coupled with large-volume sample stacking.

On-column complexation of Fe2+ and Fe3+ with 2,6-pyridinedicarboxylic acid (2,6-PDCA) formed anionic complexes, which were then separated by capillary zone electrophoresis with direct UV detection at 214 nm. To achieve reasonable separation selectivity and on-column complexation, the conditions such as pH, the concentration of 2,6-PCDA and the EOF modifiers in the electrolyte were examined. The electrolyte contained 5.0 mM 2,6-PDCA, 0.25 mM tetradecyltrimethlammonium bromide (TTAB) and 5% (v/v) acetonitrile at pH 4.0 was optimised for on-column complexation and the separation of Fe[PCDA]2(2-) and Fe[PCDA]2(-). To enhance the detection sensitivity, large-volume sample stacking (LVSS) was used for the on-line preconcentration of Fe[PCDA]2(2-) and Fe[PCDA]2(-). Under the optimised conditions, satisfactory working ranges (0.5-50 microM), lower detection limits (less than 0.1 microM) and good repeatability of the peak areas (R.S.D.: 5.2-7.8%, n = 5) was achieved using LVSS (300 s). With LVSS, the detection sensitivity was enhanced more than 50-fold compared to conventional hydrodynamic injection. The proposed method was used successfully for the determination of Fe2+ and Fe3+ in water samples.

Electrophoresis, Capillary↗

PubMed2006

Development of spherical iron(II) sulfate heptahydrate-containing solid particles with sustained drug release.

The aim of this work was to develop a simple, economic procedure for the manufacturing of coated iron(II) sulfate particles by using a crystallization technique for the development of round particles, followed by coating with a lipophilic material. Several batches of iron(II) sulfate heptahydrate were produced by a cooling crystallization, with variation of the crystallization parameters. The spherical crystals were coated with stearin. The products were characterized for particle size, roundness, bulk density and in vitro drug dissolution. Crystallization was performed from deionized water with no addition of seed crystals and by cooling by applying a linear cooling rate. The developed iron(II) sulfate crystals were round with average diameter of 729+/-165 microm. The best form for the sustained release of iron(II) sulfate was the sample HTP-2 which contained 11% of stearin relative to the iron(II) sulfate. The spherical crystallization of iron(II) sulfate is simple and fast, and does not require a dangerous, expensive solvent. The round particles can coat directly with lipophilic material which results in slow release of iron(II) sulfate and protects the iron(II) from oxidation and inhibits the loss of crystal water. The coated crystals can be filled into capsules to yield the final dosage form.

Chemistry, Pharmaceutical↗

PubMed2005

Iron complexing activity of mangiferin, a naturally occurring glucosylxanthone, inhibits mitochondrial lipid peroxidation induced by Fe2+-citrate.

Mangiferin, a naturally occurring glucosylxanthone, has been described as having antidiabetic, antiproliferative, immunomodulatory and antioxidant activities. In this study we report for the first time the iron-complexing ability of mangiferin as a primary mechanism for protection of rat liver mitochondria against Fe(2+)-citrate induced lipid peroxidation. Thiobarbituric acid reactive substances and antimycin A-insensitive oxygen consumption were used as quantitative measures of lipid peroxidation. Mangiferin at 10 microM induced near-full protection against 50 microM Fe(2+)-citrate-induced mitochondrial swelling and loss of mitochondrial transmembrane potential (DeltaPsi). The IC(50) value for mangiferin protection against Fe(2+)-citrate-induced mitochondrial thiobarbituric acid reactive substance formation (9.02+/-1.12 microM) was around 10 times lower than that for tert-butylhydroperoxide mitochondrial induction of thiobarbituric acid reactive substance formation. The xanthone derivative also inhibited the iron citrate induction of mitochondrial antimycin A-insensitive oxygen consumption, stimulated oxygen consumption due to Fe(2+) autoxidation and prevented Fe(3+) ascorbate reduction. Absorption spectra of mangiferin-Fe(2+)/Fe(3+) complexes also suggest the formation of a transient charge transfer complex between Fe(2+) and mangiferin, accelerating Fe(2+) oxidation and the formation of a more stable Fe(3+)-mangiferin complex unable to participate in Fenton-type reaction and lipid peroxidation propagation phase. In conclusion, these results show that in vitro antioxidant activity of mangiferin is related to its iron-chelating properties and not merely due to the scavenging activity of free radicals. These results are of pharmacological relevance since mangiferin and its naturally contained extracts could be potential candidates for chelation therapy in diseases related to abnormal intracellular iron distribution or iron overload.

Animals↗

PubMed2004

Simultaneous determination of Fe(II) and Fe(III) in pharmaceutical formulations with chromogenic mixed reagent by using principal component artificial neural network and multivariate calibration.

The use of chemometric approaches for the simultaneous determination of Fe(II) and Fe(III) ions has been explored by means of a two component reagent. Mixed reagents of 1,10-phenanthroline and thiocyanate were used as a selective chromogenic system for speciation of Fe(II) and Fe(III). Although the complexes of Fe(II) and Fe(III) with mixed reagent show a spectral overlap, they have been simultaneously determined with chemometric approaches, such as principal component artificial neural network (PC-ANN), principal component regression (PCR) and partial least squares (PLS). A set of synthetic mixtures of Fe(II) and Fe(III) was evaluated and the results obtained by the applications of these chemometric approaches were discussed and compared. It was found that the PC-ANN and PLS methods afforded better precision relatively than its of PCR. PC-ANN and PLS methods were also applied satisfactorily in determination of Fe(II) and Fe(III) in pharmaceutical samples.

Chemistry, Pharmaceutical↗

PubMed2005

In vivo protection of synaptosomes from oxidative stress mediated by Fe2+/H2O2 or 2,2-azobis-(2-amidinopropane) dihydrochloride by the glutathione mimetic tricyclodecan-9-yl-xanthogenate.

D609 (tricyclodecan-9-yl-xanthogenate) is a phosphatidylcholine-specific phospholipase C inhibitor that also has been reported to protect rodents against oxidative damage caused by lethal doses of ionizing radiation. We previously showed that D609 mimics glutathione. D609 has a free thiol group, which upon oxidation forms a disulfide. The resulting dixanthate is a substrate for glutathione reductase, regenerating D609. Recent studies from our laboratory have also shown that D609 reduces the Alzheimer amyloid beta-peptide (1-42)-induced oxidative stress and cytotoxicity in neuronal cell culture. The present study was undertaken to test the hypothesis that D609 would provide neuroprotection against free radical oxidative stress in vivo. Synaptosomes isolated from gerbils, previously injected intraperitoneally (ip) with D609, were treated with the oxidants Fe2+/H2O2 or 2,2-azobis-(2-amidinopropane) dihydrochloride (AAPH), which produce free radicals. Synaptosomes isolated from the gerbils ip injected with D609 and treated with Fe2+/H2O2 or AAPH showed significant reduction in reactive oxygen species, levels of protein carbonyl, protein-bound hydroxynonenal (a lipid peroxidation product), and 3-nitrotyrosine (another marker of protein oxidation formed by reaction of tyrosine residues with peroxynitrite) compared to oxidative stress in synaptosomes isolated from gerbils that were injected with saline, but treated with Fe2+/H2O2 or AAPH. These results are discussed with reference to the potential use of this brain-accessible glutathione mimetic in the treatment of oxidative stress-related neurodegenerative disorders.

Amidines↗

PubMed2005

Redox cycling of iron complexes of N-(dithiocarboxy)sarcosine and N-methyl-D-glucamine dithiocarbamate.

Iron(II)-dithiocarbamate complexes are used to trap nitrogen monoxide in biological samples, and the resulting nitrosyliron(II)-dithiocarbamate is detected and quantified by ESR. As the chemical properties of these compounds have been little studied, we investigated whether iron dithiocarbamate complexes can redox cycle. The electrode potentials of iron complexes of N-(dithiocarboxy)sarcosine (dtcs) and N-methyl-d-glucamine dithiocarbamate (mgd) are 56 and -25 mV at pH 7.4, respectively, as measured by cyclic voltammetry. The autoxidation and Fenton reaction of iron(II)-dtcs and iron(II)-mgd were studied by stopped-flow spectrophotometry with both iron(II) complexes and dioxygen or hydrogen peroxide in excess. In the case of excess iron(II)-dtcs and -mgd complexes, the rate constants of the autoxidation and the Fenton reaction are (1.6-3.2) x 10(4) and (0.7-1.1) x 10(5) M(-1) s(-1), respectively. In the presence of nitrogen monoxide, the oxidation of iron(II)-dtcs and iron(II)-mgd by hydrogen peroxide is significantly slower (ca. 10-15 M(-1) s(-1)). The physiological reductants ascorbate, cysteine, and glutathione efficiently reduce iron(III)-dtcs and iron(III)-mgd. Therefore, iron bound to dtcs and mgd can redox cycle between iron(II) and iron(III). The ligands dtcs and mgd are slowly oxidized by hydrogen peroxide with rate constants of 5.0 and 3.8 M(-1) s(-1), respectively.

Ferric Compounds↗

PubMed2005

Stabilization of heavy metals in municipal solid waste incineration ash using mixed ferrous/ferric sulfate solution.

The purpose of this study is to test the effectiveness of mixing FeSO4 and Fe2(SO4)(3) solutions with municipal solid waste incineration (MSWI) ash at room temperature to prevent heavy metals in treated ash from being dissolved. After conducting toxicity characteristic leaching procedure (TCLP) tests nine times, the accumulation of extracted lead from treated scrubber ash was lower than regulated limits by the sixth test. X-ray diffraction (XRD) and scanning electron microscopy/energy dispersive spectrometer (SEM/EDS) studies of the ash revealed that the mixed solution reacted with the scrubber ash to form Ca4Fe9O17, which coated the surface of ash particles.

Ferric Compounds↗