Showing papers on "Hydrogen peroxide published in 1987"

The Chemistry of Water Treatment Processes Involving Ozone, Hydrogen Peroxide and Ultraviolet Radiation

Abstract: Advanced oxidation processes are defined as those which involve the generation of hydroxyl radicals in sufficient quantity to affect water purification. The theoretical and (practical yield of OH from O3 at high pH, 03/H202, O3/UV and H2O2/UV systems is reviewed. New data is presented which illustrates the importance of direct photolysis in the O3/UV process, the effect of the H202:03 ratio in the O3/H2O2 process, and the impact of the low extinction coefficient of H2O2 in the H202/UV process.

Reaction kinetics of hydrogen peroxide with copper and iron in seawater.

Abstract: The oxidation of Fe(II) and Cu(I) and the reduction of Fe(III) and Cu(II) by hydrogen peroxide in sea water have been studied to understand their mechanisms and probable significance in the upper marine water column. At 10/sup -7/ M H/sub 2/O/sub 2/, a level commonly found in surface sea water, reaction with H/sub 2/O/sub 2/ is the dominant oxidation pathway for Fe(II). Reduction of Fe(III) by peroxide was not observed in the pH range 7-8. Reduction of Cu(II) and oxidation of Cu(I) by H/sub 2/O/sub 2/ contribute to a dynamic redox cycling of that element in the upper water column. Calculations based on these data indicate that CU(I) oxidation and FE(II) oxidation by H/sub 2/O/sub 2/ are at least as important as nitrite photolysis as a source of OH radicals in the ocean. 47 references, 6 figures, 2 tables.

Initiation of lipid peroxidation in biological systems

Abstract: The direct oxidation of PUFA by triplet oxygen is spin forbidden. The data reviewed indicate that lipid peroxidation is initiated by nonenzymatic and enzymatic reactions. One of the first steps in the initiation of lipid peroxidation in animal tissues is by the generation of a superoxide radical (see Figure 16), or its protonated molecule, the perhydroxyl radical. The latter could directly initiate PUFA peroxidation. Hydrogen peroxide which is produced by superoxide dismutation or by direct enzymatic production (amine oxidase, glucose oxidase, etc.) has a very crucial role in the initiation of lipid peroxidation. Hydrogen peroxide reduction by reduced transition metal generates hydroxyl radicals which oxidize every biological molecule. Hydrogen peroxide also activates myoglobin, hemoglobin, and other heme proteins to a compound containing iron at a higher oxidation state, Fe(IV) or Fe(V), which initiates lipid peroxidation even on membranes. Complexed iron could also be activated by O2- or by H2O2 to ferryl iron compound, which is supposed to initiate PUFA peroxidation. The presence of hydrogen peroxide, especially hydroperoxides, activates enzymes such as cyclooxygenase and lipoxygenase. These enzymes produce hydroperoxides and other physiological active compounds known as eicosanoids. Lipid peroxidation could also be initiated by other free radicals. The control of superoxide and perhydroxyl radical is done by SOD (a) (see Figure 16). Hydrogen peroxide is controlled in tissues by glutathione-peroxidase, which also affects the level of hydroperoxides (b). Hydrogen peroxide is decomposed also by catalase (b). Caeruloplasmin in extracellular fluids prevents the formation of free reduced iron ions which could decompose hydrogen peroxide to hydroxyl radical (c). Hydroxyl radical attacks on target lipid molecules could be prevented by hydroxyl radical scavengers, such as mannitol, glucose, and formate (d). Reduced compounds and antioxidants (ascorbic acid, alpha-tocopherol, polyphenols, etc.) (e) prevent initiation of lipid peroxidation by activated heme proteins, ferryl ion, and cyclo- and lipoxygenase. In addition, cyclooxygenase is inhibited by aspirin and nonsteroid drugs, such as indomethacin (f). The classical soybean lipoxygenase inhibitors are antioxidants, such as nordihydroguaiaretic acid (NDGA) and others, and the substrate analog 5,8,11,14 eicosatetraynoic acid (ETYA), which also inhibit cyclooxygenase (g). In food, lipoxygenase is inhibited by blanching. Initiation of lipid peroxidation was derived also by free radicals, such as NO2. or CCl3OO. This process could be controlled by antioxidants (e).(ABSTRACT TRUNCATED AT 400 WORDS)

Responses of lactic acid bacteria to oxygen

Abstract: A small number of flavoprotein oxidase enzymes are responsible for the direct interaction of lactic acid bacteria (LAB) with oxygen; hydrogen peroxide or water are produced in these reactions. In some cultures exposed to oxygen, hydrogen peroxide accumulates to inhibitory levels. Through these oxidase enzymes and NADH peroxidase, O2 and H2O2 can accept electrons from sugar metabolism, and thus have a sparing effect on the use of metabolic intermediates, such as pyruvate or acetaldehyde, as electron acceptors. Consequently, sugar metabolism in aerated cultures of LAB can be substantially different from that in unaerated cultures. Energy and biomass yields, end-products of sugar metabolism and the range of substrates which can be metabolised are affected. Lactic acid bacteria exhibit an inducible oxidative stress response when exposed to sublethal levels of H2O2. This response protects them if they are subsequently exposed to lethal concentrations of H2O2. The effect appears to be related to other stress responses such as heat-shock and is similar, in some but not all respects, to that previously reported for enteric bacteria.

Hydrogen peroxide elicits pulmonary arterial relaxation and guanylate cyclase activation.

Abstract: Hydrogen peroxide produces concentration-dependent relaxation of precontracted isolated bovine intrapulmonary arterial rings by a mechanism which is independent of the endothelium or prostaglandin mediators. Relaxant responses to hydrogen peroxide concentrations of up to 100 microM were markedly attenuated by the inhibitor of soluble guanylate cyclase activation, methylene blue (10 microM). Micromolar concentrations of hydrogen peroxide elicit time- and concentration-dependent increase in arterial levels of guanosine 3',5'-cyclic monophosphate that are associated with decreases in force. Soluble guanylate cyclase activity is markedly activated by enzymatically generated hydrogen peroxide in a manner that is most closely associated with the concentration of catalase present in the assay, by a mechanism that is inhibited by superoxide anion and the inactivation of catalase. Our data are most consistent with the involvement of compound I, a species of catalase formed during the metabolism of peroxide, in the mechanism of guanylate cyclase activation. The nature of this mechanism of arterial relaxation suggests that it could contribute to the regulation of pulmonary vascular tone by oxygen tension.

Superoxide-dependent and ascorbate-dependent formation of hydroxyl radicals from hydrogen peroxide in the presence of iron. Are lactoferrin and transferrin promoters of hydroxyl-radical generation?

Abstract: Apo-lactoferrin and apo-transferrin protect against iron-ion-dependent hydroxyl-radical (.OH) generation from H2O2 in the presence of superoxide radicals or ascorbic acid at pH 7.4, whether the necessary iron is added as ionic iron or as ferritin. Iron-loaded transferrin and lactoferrin [2 mol of Fe(III)/mol] show no protective ability, but do not themselves accelerate .OH production unless chelating agents are present in the reaction mixture, especially if the proteins are incorrectly loaded with iron. At acidic pH values, the protective ability of the apoproteins is diminished, and the fully iron-loaded proteins can release some iron in a form able to accelerate .OH generation. The physiological significance of these observations is discussed.

Metabolism of activated oxygen species

Abstract: This chapter discusses the metabolism of activated oxygen species. Oxygen exists as atomic oxygen, dioxygen, trioxygen, and several charged derivatives. Within these forms different energy levels are found because of their individual electronic configurations. The biologically important oxygen species are: (1) the superoxide radical anion, O 2 ; (2) hydrogen peroxide, H 2 O 2 ; (3) the OH radical type of oxidant (OH . ); and (4) singlet oxygen, 1 O 2 . The superoxide radical anion is formed by one electron reduction of ground-state dioxygen. The first stable product of both monovalent and divalent oxygen reduction is hydrogen peroxide, H 2 O 2 . Hydrogen peroxide can be converted into the strongly oxidizing OH radical (OH . ) by one-electron transfer. Singlet oxygen, 1 O 2 (1Δ g ) is a physically energized form of dioxygen. In contrast to ground-state dioxygen, 1 O 2 has Π* electrons with antiparallel spins; thus, its reactions with other ground-state atoms or molecules are not spin restricted and proceed at appreciable rates.

Oxidative stress in chemical toxicity.

Abstract: The toxic effects of compounds which undergo redox cycling via enzymatic one-electron reduction are reviewed. First of all, the enzymatic reduction of these compounds leads to reactive intermediates, mainly radicals which react with oxygen, whereby superoxide anion radicals are formed. Further oxygen metabolites are hydrogen peroxide, singlet oxygen and hydroxyl radicals. The role of these oxygen metabolites in toxicity is discussed. The occurrence of lipid peroxidation during redox cycling of quinonoide compounds, e.g., adriamycin, and the possible relationship to their toxicity is critically evaluated. It is shown that iron ions play a crucial role in lipid peroxidation induced by redox cycling compounds. DNA damage by metal chelates, e.g., bleomycin, is discussed on the basis of findings that enzymatic redox cycling of a bleomycin-iron complex has been observed. The involvement of hydroxyl radicals in bleomycin-induced DNA damage occurring during redox cycling in cell nuclei is claimed. Redox cycling of other substances, e.g., aromatic amines, is discussed in relation to carcinogenesis. Other chemical groups, e.g., nitroaromatic compounds, hydroxylamines and azo compounds are included. Other targets for oxygen radical attack, e.g., proteins, are also dealt with. It is concluded that oxygen radical formation by redox cycling may be a critical event in toxic effects of several compounds if the protective mechanisms of cells are overwhelmed.

Hydroxyl radical production and human DNA damage induced by ferric nitrilotriacetate and hydrogen peroxide.

Abstract: Reactivities of Fe 3+ chelates of aminopolycarboxylic acids with DNA were investigated by the DNA-sequencing technique using 32 P 5′-end-labeled DNA fragments obtained from the human c-Ha- ras -1 protooncogene, and the reaction mechanism was studied by electron spin resonance spectroscopy. Ferric nitrilotriacetate (Fe 3+ -NTA) plus hydrogen peroxide caused strong DNA cleavage in the presence of albumin. No or little DNA cleavage was observed with ferric chloride or Fe 3+ chelates of other aminopolycarboxylic acids tested in the presence of hydrogen peroxide. The DNA cleavage by Fe 3+ -NTA plus hydrogen peroxide without piperidine treatment occurred at positions of every nucleotide although a specific cleavage was observed, whereas cleavages at the positions of guanine and thymine increased predominantly with piperidine treatment. Electron spin resonance studies using free radical traps demonstrated that of Fe 3+ chelates of aminopolycarboxylic acids, Fe 3+ -NTA was the most effective catalyst in hydrogen peroxide-derived production of hydroxyl radicals under our conditions. The results suggest that Fe 3+ -NTA catalyzes the decomposition of hydrogen peroxide to produce hydroxyl radicals, which subsequently cause the strong base alterations of guanine and thymine, and deoxyribose-phosphate backbone breakages. The possibility that the Fe 3+ -NTA-induced DNA damage is the initiation and/or promotion of carcinogenesis by Fe 3+ -NTA is discussed.

Fate of superoxide in coastal sea water

Abstract: The superoxide anion (O2.− ) is a key intermediate in oxygen redox chemistry, and may mediate many chemical transformations in the ocean. The photochemical formation of hydrogen peroxide in sea water has been postulated1 to result from the disproportionation of superoxide, and here we report the results of a study which used the formation of H2O2 to characterize the dynamics of superoxide in coastal sea water. Midday rates of superoxide generation averaged ∼5 x 10-7 mol 1-1h-1. In addition to rapid disproportionation to hydrogen peroxide, a substantial fraction of the superoxide flux was shunted off through unknown pathways; 24–41% of the superoxide flux did not lead directly to H2O2 formation. Our calculations predicted accelerated decomposition of super-oxide in natural sea water relative to pure water; nevertheless, superoxide should be a relatively long-lived transient in sea water. We calculate the 50% decay time of a 10-8mol 1-1 steady-state level to be 20 min.

Photoinduced generation of hydrogen peroxide and hydroxyl radicals in melanins

Abstract: The hydrogen peroxide produced during photolysis of melanin pigments has been measured using an oxidase electrode. The photooxidation has been shown to occur via the superoxide intermediate. In the presence of superoxide dismutase the rate of photo-induced production of hydrogen peroxide is increased, reflecting the ability of melanin to scavenge superoxide radicals. Evidence for metal-ion dependent formation of hydroxyl radicals during photooxidation of melanin pigments was obtained using electron spin resonance-spin trapping procedures. Superoxide dismutase increased the rate of formation of hydroxyl radicals in the system. Mechanisms of metal ion-induced production of hydroxyl radicals during photolysis of melanin pigments are discussed.

Use of azide and hydrogen peroxide as an inhibitor for endogenous peroxidase in the immunoperoxidase method.

Abstract: We describe a simple and effective method for inhibition of endogenous peroxidase activity in the immunoperoxidase technique. Specimens are pre-treated with a mixture of azide and hydrogen peroxide, which is then followed by an indirect immunoperoxidase procedure. Comparison studies showed no significant loss of antigenicity or morphological details by this pre-treatment. The method is most useful for evaluating cell-specific antigens on specimens that have abundant endogenous peroxidase activity, such as blood and bone marrow.

Aqueous phase oxidation of sulfur(IV) by hydrogen peroxide, methylhydroperoxide, and peroxyacetic acid

Abstract: The aqueous phase oxidation kinetics of sulfur(IV) by hydrogen peroxide, methylhydroperoxide, and peroxyacetic acid have been investigated over the pH range 4.0–5.2 for hydrogen peroxide and methylhydroperoxide and 2.9–5.8 for peroxyacetic acid. The reagent concentrations used in these studies were in the micromolar range. In the cases of hydrogen peroxide and peroxyacetic acid, 1 mol of sulfate was produced for each mole of peroxide consumed. In the case of methylhydroperoxide, 0.73±0.04 mol of sulfate, and 0.27±0.04 mol of the methylsulfate were produced for each mole of peroxide consumed. The experimentally determined rate laws for the three reactions are given by d[peroxide]/dt = k[H+] [peroxide] [S(IV)]. The third order rate constants, k, for the three reactions were determined to be 7.2±2.0×107 M−2s−1 for hydrogen peroxide (18°C), 1.7±0.4×107 M−2s−1 for methylhydroperoxide (23°C), and 3.5±1.3 ×107 M−2s−1 for peroxyacetic acid (18°C). The oxidation kinetics of aqueous S(IV) by peroxyacetic acid also contained a second-order term over the pH range investigated in this study, first-order in both peroxyacetic acid and S(IV) concentrations. The rate constant k′ for this term was determined to be 6.1±2.6×102 M−1s−1. Temperature dependence studies over the range 6°–25°C yielded activation energies of 31.6±1.3 kJ/mol for methylhydroperoxide and 33.2±0.7 kJ/mol for peroxyacetic acid.

Human red cells scavenge extracellular hydrogen peroxide and inhibit formation of hypochlorous acid and hydroxyl radical.

Abstract: The ability of intact human red cells to scavenge extracellularly generated H2O2 and O2-, and to prevent formation of hydroxyl radicals and hypochlorous acid has been examined. Red cells inhibited oxidation of ferrocytochrome c by H2O2. Cells treated with aminotriazole no longer inhibited, indicating that protection was almost entirely due to intracellular catalase. Contribution by the GSH system was slight, and apparent only with low H2O2 concentrations when catalase was inhibited by aminotriazole. The cells were about a quarter as efficient at inhibiting cytochrome c oxidation as an equivalent concentration of purified catalase. No inhibition of O2(-)-dependent reduction of ferricytochrome c or nitroblue tetrazolium was observed, although extracted red cell superoxide dismutase inhibited nitroblue tetrazolium reduction at one fortieth the concentration of that in the cells. Red cells efficiently inhibited deoxyribose oxidation by hydroxyl radicals generated from H2O2, O2- and Fe(EDTA), and myeloperoxidase-dependent oxidation of methionine to methionine sulfoxide by stimulated neutrophils. Most of the red cell inhibition of hydroxyl radical production, and all the inhibition of methionine oxidation, was prevented by blocking intracellular catalase with aminotriazole. Thus red cells are able to efficiently scavenge H2O2, but not O2-, produced in their environment, and to inhibit formation of hydroxyl radicals and hypochlorous acid. They may therefore have an important role in extracellular antioxidant defense.

Mechanistic studies on the cobalt(II) Schiff base catalyzed oxidation of olefins by O2

Abstract: The cobalt complex (bis(salicylidene-..gamma..-iminopropyl)methylamine)cobalt(II), CoSMDPT, has been shown to catalytically oxidize olefins in the presence of dioxygen or hydrogen peroxide. When terminal olefins are oxidized, the methyl ketone and corresponding secondary alcohol are produced selectively. Internal as well as terminal olefins are oxidized. The most common pathway for the oxidation of olefins catalyzed by first-row transition metals-autoxidation-has been ruled out in this system. A Wacker-type mechanism, oxidation by peracids, and mechanisms involving the formation of peroxymetallocycles have also been ruled out. A new mechanism for O/sub 2/ oxidations is proposed which involves oxidation of the primary alcohol solvent by CoSMDPT to produce the corresponding aldehyde and hydrogen peroxide. Reaction of hydrogen peroxide with CoSMDPT occurs to form a cobalt hydroperoxide, which can be viewed as a stabilized hydroperoxy radical which has spin paired with the d/sub z/sup 2// electron of CoSMDPT. The cobalt hydroperoxide then adds to the olefin double bond, leading to formation of an alkyl hydroperoxide. Haber-Weiss decomposition of this alkyl hydroperoxide by CoSMDPT produces the observed ketone and alcohol products. Deactivation of the catalyst is due to oxidation of the ligand system of the cobalt complex as well as formation of a ..mu..-peroxo-dicobalt complex.

Interaction between oxygen radicals and gastric mucin.

Abstract: The gastrointestinal epithelium is continuously exposed to reactive oxygen metabolites that are generated within the lumen. In spite of this exposure, the healthy epithelium appears unaffected, suggesting efficient mechanisms for protection against these potentially cytotoxic oxidants. The objective of this study is to characterize the interaction between purified gastric mucin and hydroxyl radicals generated from the interaction between ferric iron and ascorbic acid. We found that both native and pronase-treated mucin effectively scavenged hydroxyl radical and that the scavenging properties were not significantly different. The effective concentration of mucin required for a 50% reduction in malondialdehyde production was approximately 10 mg/ml for both native and pronase-treated mucin. In addition, the iron-ascorbic system produced a dramatic decrease (greater than 50%) in the specific viscosity of mucin that was inhibited by catalase, deferoxamine, and mannitol. Superoxide dismutase had no effect. These data suggest that hydroxyl radicals derived from the iron-catalyzed decomposition of hydrogen peroxide are responsible for the depolymerization of native mucin. We propose that mucin may provide protection to the surface epithelium of the gastrointestinal tract by scavenging oxidants produced within the lumen; however, it does so at the expense of its viscoelastic properties.

The antioxidant action of human extracellular fluids. Effect of human serum and its protein components on the inactivation of alpha 1-antiproteinase by hypochlorous acid and by hydrogen peroxide.

Abstract: The elastase-inhibitory capacity of purified human alpha 1-antiproteinase is inactivated by low concentrations of the myeloperoxidase-derived oxidant hypochlorous acid, but much higher concentrations are required to inhibit the elastase-inhibitory capacity of serum samples The protective effect of serum appears to be largely due to albumin High concentrations of H2O2 also inactivate the elastase-inhibitory capacity of alpha 1-antiproteinase, by a mechanism not involving formation of hydroxyl radicals Serum offers protection against H2O2 inactivation of alpha 1-antiproteinase The relevance of these results to the tissue damage produced by activated phagocytes is discussed

Gentamicin enhanced production of hydrogen peroxide by renal cortical mitochondria

Abstract: Agents that affect mitochondrial respiration have been shown to enhance the generation of reactive oxygen metabolites. On the basis of the well-demonstrated ability of gentamicin to alter mitochondrial respiration (stimulation of state 4 and inhibition of state 3), it was postulated that gentamicin may enhance the generation of reactive oxygen metabolites by renal cortical mitochondria. The aim of this study was to examine the effect of gentamicin on the production of hydrogen peroxide (measured as the decrease in scopoletin fluorescence) in rat renal cortical mitochondria. The hydrogen peroxide generation by mitochondria was enhanced from 0.17 +/- 0.02 nmol . mg-1 . min-1 (n = 14) in the absence of gentamicin to 6.21 +/- 0.67 nmol . mg-1 . min-1 (n = 14) in the presence of 4 mM gentamicin. This response was dose dependent with a significant increase observed at even the lowest concentration of gentamicin tested, 0.01 mM. Production of hydrogen peroxide was not increased when gentamicin was added to incubation media in which mitochondria or substrate was omitted or heat-inactivated mitochondria were used. The gentamicin-induced change in fluorescence was completely inhibited by catalase (but not by heat-inactivated catalase), indicating that the decrease in fluorescence was due to hydrogen peroxide. Thus this study demonstrates that gentamicin enhances the production of hydrogen peroxide by mitochondria. Because of their well-documented cytotoxicity, reactive oxygen metabolites may play a critical role in gentamicin nephrotoxicity.