Showing papers on "Hydrogen peroxide published in 2000"
TL;DR: In this article, the transformation of superoxide into hydrogen peroxide and, under certain conditions, then into hydroxyl radicals is important in diseases where respiratory chain function is abnormal or where superoxide dismutase function is altered.
1,049 citations
TL;DR: A large number of highly reactive microbicidal oxidants are formed, including HOCl (hypochlorous acid), which is produced by the myeloperoxidase-catalyzed oxidation of Cl(-) by H(2)O(2); OH(*) (hydroxyl radical); ONOO(-) (peroxynitrite), formed by the reaction between O(2)(-) and NO(*); and many others.
1,030 citations
TL;DR: Urinary H2O2 levels are influenced by diet, but under certain conditions might be a valuable biomarker of ‘oxidative stress’.
960 citations
TL;DR: Iron metabolism, and its coupling with regulation of defenses against oxidative stress, as well as the role played by iron in regulatory protein in sensing redox change, appear as essential factors for life in the presence of oxygen.
833 citations
TL;DR: Blackberries had the highest antioxidant capacity inhibition of O(2)(*)(-), H(2)O(2), and OH(*).
Abstract: The antioxidant activities against superoxide radicals (O2•-), hydrogen peroxide (H2O2), hydroxyl radicals (OH•), and singlet oxygen (‘O2) was evaluated in fruit juice from different cultivars of thornless blackberries (Rubus sp.), blueberries (Vaccinium spp.), cranberries (Vaccinium macrocarpon Aiton), raspberries (Rubus idaeus L. and Rubus occidentalis L.), and strawberries (Fragaria x ananassa Duch.). Among the different cultivars, juice of ‘Hull Thornless' blackberry, ‘Earliglow' strawberry, ‘Early Black' cranberry, ‘Jewel' raspberry, and ‘Elliot' blueberry had the highest antioxidant capacity against superoxide radicals (O2•-), hydrogen peroxide (H2O2), hydroxyl radicals (OH•), and singlet oxygen (‘O2). In general, blackberries had the highest antioxidant capacity inhibition of O2•-, H2O2, and OH•. Strawberry was second best in the antioxidant capacity assay for these same free radicals. With regard to ‘O2 scavenging activity, strawberry had the highest value, while blackberry was second. Cranberries...
599 citations
TL;DR: In this article, the amount of the organic substances removed by oxidation and coagulation in treatment of the non-biodegradable landfill leachate by Fenton's reagents was analyzed.
558 citations
TL;DR: In this paper, the authors used ozone and ozone/hydrogen peroxide (advanced oxidation process) to degrade the pharmaceuticals and showed that ozone and hydrogen peroxide leading to OH-radical formation improved the degradation efficiency of all investigated compounds.
506 citations
TL;DR: The results strongly suggest that the oxidative stress in prokaryotic and eukaryotic cells shares common features.
454 citations
TL;DR: These resting state and inhibited humanCatalase structures support specific, structure-based mechanisms for the catalase substrate recognition, reaction and inhibition and provide a molecular basis for understanding ethanol intoxication and the likely effects of human polymorphisms.
412 citations
TL;DR: The attractive performance characteristics of the glutamate biosensor illustrate the advantages of Prussian Blue-based "artificial peroxidase" as transducer for hydrogen peroxide detection.
Abstract: The specially deposited Prussian Blue denoted as “artificial peroxidase” was used as a transducer for hydrogen peroxide. The electrocatalyst was stable, highly active, and selective to hydrogen peroxide reduction in the presence of oxygen, which allowed sensing of H2O2 around 0.0 V (Ag/AgCl). Glutamate oxidase was immobilized on the surface of the Prussian Blue-modified electrode in a Nafion layer using a nonaqueous enzymology approach. The calibration range for glutamate in flow injection system was 1 × 10-7−1 × 10-4 M. The lowest concentration of glutamate detected (1 × 10-7 M) and the highest sensitivity in the linear range of 0.21 A M-1 cm-2 were achieved. The influence of reductants was practically avoided using the low potential of an indicator electrode (0.0 V Ag/AgCl). The attractive performance characteristics of the glutamate biosensor illustrate the advantages of Prussian Blue-based “artificial peroxidase” as transducer for hydrogen peroxide detection.
399 citations
TL;DR: In this paper, the second-order rate constants for sulfide oxidations by peroxymonocarbonate ion (HCO4-) are ∼300-fold greater than those for H2O2, and this increase is consistent with expectations based on expectations.
Abstract: Bicarbonate ion is an effective activator for hydrogen peroxide in the oxidation of sulfides. Kinetic and spectroscopic results support the formation of peroxymonocarbonate ion (HCO4-) as the oxidant in the catalytic reactions. The reaction of hydrogen peroxide and bicarbonate to form HCO4- occurs rapidly at 25 °C (t1/2 ≈ 300 s) near neutral pH in aqueous solution and alcohol/water mixtures, and an equilibrium analysis of the reaction by 13C NMR leads to an estimate of the electrode potential for the HCO4-/HCO3- couple (1.8 V vs NHE). Solubility of the bicarbonate catalyst is enhanced by the use of NH4HCO3 rather than by the use of group 1 salts, which tend to have lower solubility in the mixed solvents and can lead to phase separation. Rate laws and mechanistic analyses are presented for the oxidation of ethylphenylsulfide and related sulfides. The second-order rate constants for sulfide oxidations by HCO4- are ∼300-fold greater than those for H2O2, and this increase is consistent with expectations based...
TL;DR: In this paper, the possibility of using electrochemically produced hydroxyl radicals for solving environmental problems is investigated, which is achieved by electrochemical reduction of O2 in the presence of a catalytic amount of ferric or ferrous ion.
Abstract: The electrochemical production of Fenton’s reagent by simultaneous reduction of dioxygen and ferric ions on a carbon felt electrode, permits a controlled, in situ generation of hydroxyl (OH AE ) radicals. The possibility of using electrochemically produced OH AE radicals for solving environmental problems is investigated. Continuous and controlled production of hydroxyl radicals was achieved by electrochemical reduction of O2 in the presence of a catalytic amount of ferric or ferrous ion. These radicals are used for remediation of water containing toxic-persistent-bioaccumulative organic pollutants through their transformation into biodegradable compounds or through their mineralization into H2O and CO2. A widely used herbicide, 2,4-dichlorophenoxyacetic acid (2,4-D), was selected as a model for a toxic organic pollutant. High pressure liquid chromatography (HPLC) was used to quantify the distribution of the hydroxylated products obtained. Rate constants for the hydroxylation reactions of 2,4-D, 2,4-dichlorophenol (2,4-DCP), 2,4-dichlororesorcinol (2,4-DCR) and 4,6-dichlororesorcinol (4,6-DCR) were determined. The mineralization of 2,4-D and its derivatives was followed by total organic carbon (TOC) measurements. More than 95% of 2,4-D and the intermediates generated during the electrolysis can be mineralized.
TL;DR: The endogenous antioxidative defense system reduces molecular toxicity of oxygen and nitrogen-based reactive species and neutralizes other toxic species, including singlet oxygen, hydrogen peroxide, nitric oxide, and peroxynitrite anion.
Abstract: The endogenous antioxidative defense system reduces molecular toxicity of oxygen and nitrogen-based reactive species. Melatonin is an efficient direct and indirect antioxidant. It detoxifies the highly reactive hydroxyl radical and neutralizes other toxic species, including singlet oxygen, hydrogen peroxide, nitric oxide, and peroxynitrite anion, and stimulates several antioxidative enzymes.
TL;DR: Results indicate that hydrogen peroxide production is heritable and is related to target organ function in essential hypertension, and genetic loci influencing hydrogenperoxide production may represent logical candidates to investigate as susceptibility genes for cardiovascular target organ injury.
Abstract: Oxygen free radicals, including hydrogen peroxide, may mediate oxidative stress in target organ tissues and contribute to cardiovascular complications in hypertension. To examine heritability of hydrogen peroxide production, we investigated this trait in a family-based cohort consisting of family members (n=236) ascertained through probands (n=57) with essential hypertension. Significant effects on hydrogen peroxide production were found for gender and ethnicity, with men having greater values than women (P<0.001) and white subjects having greater values than black subjects (P=0.025). Hydrogen peroxide production correlated directly with plasma renin activity (P=0.015), suggesting an important interaction between circulating oxygen radicals and the renin-angiotensin system and a potential mechanism for lower hydrogen peroxide values observed in blacks. Heritability estimates from familial correlations revealed that approximately 20% to 35% of the observed variance in hydrogen peroxide production could be attributed to genetic factors, suggesting a substantial heritable component to the overall determination of this trait. Hydrogen peroxide production negatively correlated with cardiac contractility (r=-0.214, P=0.001) and renal function (r=-0.194, P=0.003). In conclusion, these results indicate that hydrogen peroxide production is heritable and is related to target organ function in essential hypertension. Genetic loci influencing hydrogen peroxide production may represent logical candidates to investigate as susceptibility genes for cardiovascular target organ injury.
TL;DR: In this article, the behavior of a heterogeneous Fe3+-containing zeolite (Fe/ZSM5) was compared with the behaviour of homogeneous Fe 3+ catalysts at the same experimental conditions.
TL;DR: Data indicate that flavonoids inhibit platelet function by blunting hydrogen peroxide production and, in turn, phospholipase C activation and suggest that the synergism among flavonoid could contribute to an understanding of the relation between the moderate consumption of red wine and the decreased risk of cardiovascular disease.
TL;DR: In this article, the effects of hydrogen peroxide dosage, initial phenol concentration, H2O2/phenol molar ratio, pH, and temperature have been investigated in a completely mixed, batch photolytic reactor.
TL;DR: A model in which various stress situations that lead to the production of hydrogen peroxide can be ameliorated by elaboration of the peroxisome compartment to assist in restoration of the cellular redox balance is proposed.
Abstract: Peroxisomes are the cellular location of many antioxidants and are themselves significant producers of reactive oxygen species. In this report we demonstrate the induction of peroxisome biogenesis genes in both plant and animal cells by the universal stress signal molecule hydrogen peroxide. Using PEX1–LUC transgenic plants, rapid local and systemic induction of PEX1–luciferase could be demonstrated in vivo in response to physiological levels of hydrogen peroxide. PEX1–luciferase was also induced in response to wounding and to infection with an avirulent pathogen. We propose a model in which various stress situations that lead to the production of hydrogen peroxide can be ameliorated by elaboration of the peroxisome compartment to assist in restoration of the cellular redox balance.
TL;DR: Hydroxyl radical formation rate and time dependent concentration were determined in pure water, in aqueous fulvic acid and humic acid solutions, and in natural surface waters, while increased radical formation was observed with FA at certain pH values.
TL;DR: In this article, the dewaxed rice straw with 1% NaOH at 55°C for 2h and then following treatment with 0.0% H 2 O 2 at pH 11.5 solubilized 67.2, 77.7, 83.5, 87.3, 85.4, 89.4 and 95.1% of the original lignin under the conditions given, respectively.
TL;DR: The current knowledge of gas-phase hydrogen peroxide and organic hydroperoxide in the troposphere is reviewed in this paper, where chemistry, properties, measurement methodology and tropospheric distribution are discussed.
TL;DR: This novel method revealed that lipid peroxidation proceeded within membranes of PMNs stimulated with phorbol 12‐myristate 13‐acetate, which is known to produce several kinds of free radicals.
TL;DR: In this article, an enhanced photocatalytic degradation of microcystin-LR following the addition of hydrogen peroxide to the water treatment system was investigated, however no HPLC detectable by-products were found.
Abstract: Cyanobacterial toxins present in drinking water sources pose a considerable threat to human health. Conventional water treatment systems have proven unreliable for the removal of these toxins and hence new techniques have been investigated. Previous work has shown that TiO 2 photocatalysis effectively destroys microcystin-LR in aqueous solutions, however non-toxic by-products were detected. It has been shown that photocatalytic reactions are enhanced by utilisation of alternative electron acceptors. We report here enhanced photocatalytic degradation of microcystin-LR following the addition of hydrogen peroxide to the system. It was also found that hydrogen peroxide with UV illumination alone was capable of decomposing microcystin-LR although at a much slower rate than found for TiO 2 . No HPLC detectable by-products were found when the TiO 2 /UV/H 2 O 2 system was used indicating that this method is more effective than TiO 2 /UV alone. Results however indicated that only 18% mineralisation occurred with the TiO 2 /UV/H 2 O 2 system and hence undetectable by-products must still be present. At higher concentrations hydrogen peroxide was found to compete with microcystin-LR for surface sites on the catalyst but at lower peroxide concentrations this competitive adsorption was not observed. Toxicity studies showed that both in the presence and absence of H 2 O 2 the microcystin solutions were detoxified. These findings suggest that hydrogen peroxide greatly enhances the photocatalytic oxidation of microcystin-LR.
TL;DR: The observation that heme degradation was inhibited by compounds, which react with ferrylHb such as sodium sulfide, and peroxidase substrates (ABTS and o-dianisidine), demonstrates that ferryl Hb formation is required for heme degraded products.
Abstract: The reaction of Fe(II) hemoglobin (Hb) but not Fe(III) hemoglobin (metHb) with hydrogen peroxide results in degradation of the heme moiety. The observation that heme degradation was inhibited by compounds, which react with ferrylHb such as sodium sulfide, and peroxidase substrates (ABTS and o-dianisidine), demonstrates that ferrylHb formation is required for heme degradation. A reaction involving hydrogen peroxide and ferrylHb was demonstrated by the finding that heme degradation was inihibited by the addition of catalase which removed hydrogen peroxide even after the maximal level of ferrylHb was reached. The reaction of hydrogen peroxide with ferrylHb to produce heme degradation products was shown by electron paramagnetic resonance to involve the one-electron oxidation of hydrogen peroxide to the oxygen free radical, superoxide. The inhibition by sodium sulfide of both superoxide production and the formation of fluorescent heme degradation products links superoxide production with heme degradation. The inability to produce heme degradation products by the reaction of metHb with hydrogen peroxide was explained by the fact that hydrogen peroxide reacting with oxoferrylHb undergoes a two-electron oxidation, producing oxygen instead of superoxide. This reaction does not produce heme degradation, but is responsible for the catalytic removal of hydrogen peroxide. The rapid consumption of hydrogen peroxide as a result of the metHb formed as an intermediate during the reaction of reduced hemoglobin with hydrogen peroxide was shown to limit the extent of heme degradation.
TL;DR: The catalyzed kinetics of the oxidative mineralization of the cationic dye methylene blue, phenothiazonium, 3,7-bis(dimethylamino)-chloride, with hydrogen peroxide were studied both in buffered and unbuffered solutions and a reaction mechanism was proposed with the formation of free radicals as reactive intermediates.
TL;DR: The improvement in the decomposition levels reached by the combined processes, due to the generation of the very reactive hydroxyl radicals, in relation to the single oxidants is clearly demonstrated and evaluated by kinetic modeling.
TL;DR: The reaction of kynurenine pathway catabolites with copper and iron, as well as interactions with the major lenticular structural proteins, the alpha-crystallins, support the possibility that 3HK and 3HAA may be cofactors in the oxidative damage of proteins through interactions with redox-active metals and especially copper.
Abstract: The kynurenine pathway catabolite 3-hydroxykynurenine (3HK) and redox-active metals such as copper and iron are implicated in cataractogenesis. Here we investigate the reaction of kynurenine pathway catabolites with copper and iron, as well as interactions with the major lenticular structural proteins, the alpha-crystallins. The o-aminophenol kynurenine catabolites 3HK and 3-hydroxyanthranilic acid (3HAA) reduced Cu(II)>Fe(III) to Cu(I) and Fe(II), respectively, whereas quinolinic acid and the nonphenolic kynurenine catabolites kynurenine and anthranilic acid did not reduce either metal. Both 3HK and 3HAA generated superoxide and hydrogen peroxide in a copper-dependent manner. In addition, 3HK and 3HAA fostered copper-dependent alpha-crystallin cross-linking. 3HK- or 3HAA-modifed alpha-crystallin showed enhanced redox activity in comparison to unmodified alpha-crystallin or ascorbate-modified alpha-crystallin. These data support the possibility that 3HK and 3HAA may be cofactors in the oxidative damage of proteins, such as alpha-crystallin, through interactions with redox-active metals and especially copper. These findings may have relevance for understanding cataractogenesis and other degenerative conditions in which the kynurenine pathway is activated.
TL;DR: In this paper, the degradation of the pesticide precursor 4-chlorobenzoic acid (4-CBA) in water was investigated using different TiO 2 powders and near-UV radiation.
Abstract: Assisted-photocatalytic degradation of the pesticide precursor 4-chlorobenzoic acid (4-CBA) in water was investigated using different TiO 2 powders and near-UV radiation. Experiments were performed at pH=3.0 and at different TiO 2 loadings, solution ionic strengths, and concentrations of hydrogen peroxide as an oxidant additive. Dark adsorption equilibrium studies revealed that surface area, ionic strength, and catalyst heterogeneity influenced the adsorption capacity and adsorption mechanism. This was attributed to the type and concentration of adsorption sites and the electrostatic interactions in the solution-semiconductor interface. However, the rates of the photocatalytic reactions were not significantly affected by an increase in the ionic strength by a factor of 50. On the other hand, the reaction rate was a strong function of catalyst crystallinity and loading. This suggested that the reactions were mostly controlled by the rate of formation of the oxidizing species rather than the extent of electric double layer (EDL) compression. Addition of hydrogen peroxide up to 248 mg/l resulted in an increase of the reaction rates with a corresponding increase in photonic efficiency by ≈20%. Above this concentration, hydrogen peroxide either did not enhance or caused a significant inhibition of the mineralization rates.
TL;DR: The penetration of hydrogen peroxide into biofilms formed by wild-type and catalase-deficient Pseudomonas aeruginosastrains was measured using microelectrodes andcatalase protects aggregated bacteria by preventing full penetration of Hydrogen Peroxide into the biofilm.
Abstract: The penetration of hydrogen peroxide into biofilms formed by wild-type and catalase-deficient Pseudomonas aeruginosa strains was measured using microelectrodes. A flowing stream of hydrogen peroxide (50 mM, 1 h) was unable to penetrate or kill wild-type biofilms but did penetrate and partially kill biofilms formed by an isogenic strain in which the katA gene was knocked out. Catalase protects aggregated bacteria by preventing full penetration of hydrogen peroxide into the biofilm.
TL;DR: In this article, the bicarbonate-catalyzed epoxidation of alkenes with aqueous hydrogen peroxide at near neutral pH is described, which is comparable in apparent synthetic utility to the best methods now available for H2O2-based alkene expoxidations that avoid extensive hydrolytic formation of diol.
Abstract: We describe here the discovery of the bicarbonate-catalyzed epoxidation of alkenes with aqueous hydrogen peroxide at nearneutral pH. For some substrates, the procedure is comparable in apparent synthetic utility to the best methods now available for H2O2-based alkene expoxidations that avoid extensive hydrolytic formation of diol (e.g., ligand-accelerated methyltrioxorhenium/ H2O2). The new process features a stable main group catalyst/ activator of unexpected simplicity (bicarbonate ion) and can be applied readily in water or mixed aqueous solutions under homogeneous conditions. Hydrogen peroxide is a high oxygen content, environmentally friendly oxidant for which water is the sole byproduct in heterolytic oxidations,2 but it is a slow oxidant in the absence of activation3 due to the poor leaving tendency of the hydroxide ion.4 Transition metal salts or complexes have been used as catalysts for alkene epoxidations with aqueous H2O2 .5,6 Other methods for activation of H2O2 include forming reactive peroxyacids from carboxylic acids,7 forming peroxycarboximidic acid from acetonitrile (Payne oxidation),8 generation of peroxyisourea,9 or using sodium perborate or sodium percarbonate (Na2CO3‚1.5H2O2) in strongly basic solution.10 Such systems can have one or more disadvantages, such as toxic or rapidly decomposed metal catalysts, oxidative decomposition of organic ligands, organic byproducts, or strongly acidic or basic reaction conditions that decompose the desired epoxide product. A method for activating hydrogen peroxide with bicarbonate ion was described by Drago and co-workers11 and Richardson et al.12 in their studies of sulfide oxidations in alcohol/water solvents. In the bicarbonate-activated peroxide (BAP) system,13 the active oxidant peroxymonocarbonate ion, HCO4, is formed with t1/2 ≈ 5 min (eq 1), presumably via the perhydration of CO2