ascorbic-acid and sodium-borohydride

Eumelanin photoprotects pigmented tissues from ultraviolet (UV) damage. However, UVA-induced tanning seems to result from the photooxidation of preexisting melanin and does not contribute to photoprotection. We investigated the mechanism of UVA-induced degradation of 5,6-dihydroxyindole-2-carboxylic acid (DHICA)-melanin taking advantage of its solubility in a neutral buffer and using a differential spectrophotometric method to detect subtle changes in its structure. Our methodology is suitable for examining the effects of various agents that interact with reactive oxygen species (ROS) to determine how ROS is involved in the UVA-induced oxidative modifications. The results show that UVA radiation induces the oxidation of DHICA to indole-5,6-quinone-2-carboxylic acid in eumelanin, which is then cleaved to form a photodegraded, pyrrolic moiety and finally to form free pyrrole-2,3,5-tricarboxylic acid. The possible involvement of superoxide radical and singlet oxygen in the oxidation was suggested. The generation and quenching of singlet oxygen by DHICA-melanin was confirmed by direct measurements of singlet oxygen phosphorescence.

Topics: Animals; Ascorbic Acid; Borohydrides; Cattle; Hydrogen Peroxide; Indoles; Luminescence; Melanins; Oxidation-Reduction; Reactive Oxygen Species; Singlet Oxygen; Spectrophotometry; Spectroscopy, Near-Infrared; Time Factors; Ultraviolet Rays

The formation of disinfection by-products (DBPs) is a public health concern due to their potential adverse health effects. Robust and sensitive methods for the analysis of DBPs, as well as appropriate sample handling procedures, are essential to obtain accurate, precise and reliable data on DBP occurrence and formation. In particular, the use of an appropriate quenching agent is critical to prevent further formation of DBPs during the holding time between sample collection and analysis. Despite reports of decomposition of DBPs caused by some quenching agents, particularly sulphite and thiosulphate, a survey of the literature shows that they are still the most commonly used quenching agents in analysis of DBPs. This study investigated the effects of five quenching agents (sodium sulphite, sodium arsenite, sodium borohydride, ascorbic acid, and ammonium chloride) on the stability of seven different classes of DBPs commonly found in drinking waters, in order to determine the most appropriate quenching agent for the different classes of DBPs. All of the quenching agents tested did not adversely affect the concentrations of trihalomethanes (THMs) and haloacetic acids (HAAs), and thus are suitable for quenching of disinfectant residual prior to analysis of these DBPs. Ascorbic acid was found to be suitable for the analysis of haloacetonitriles (HANs) and haloketones (HKs), but should not be used for the analysis of chlorite. Sodium arsenite, sodium borohydride, and ascorbic acid were all acceptable for the analysis of haloacetaldehydes (HALs). All of the quenching agents tested adversely affected the concentration of chloropicrin. A 'universal' quenching agent, suitable for all groups of DBPs studied, was not identified. However, based on the results of this study, we recommend the use of ascorbic acid for quenching of samples to be analysed for organic DBPs (i.e. THMs, HAAs, HANs, HKs, and HALs) and sodium sulphite for analysis of inorganic DBPs. Our study is the first comprehensive study on the effects of quenching agents on the stability of DBPs involving a wide range of DBP classes and quenching agents.

Topics: Ammonium Chloride; Arsenites; Ascorbic Acid; Borohydrides; Disinfectants; Disinfection; Drinking Water; Environmental Monitoring; Sensitivity and Specificity; Sodium Compounds; Sulfites; Trihalomethanes; Water; Water Pollutants, Chemical; Water Supply

Cellular redox status and oxygen availability influence the product formation. Herein, decreasing agitation speed or adding vitamin C (Vc) achieved the 2,3-BDL yield of 0.40 g g(-1) or 0.39 g g(-1)glucose under batch fermentation, respectively. To our knowledge, this is the highest 2,3-BDL yield reported so far for Paenibacillus polymyxa without adding acetic acid. The NADH/NAD(+) ratio and 2,3-BDL titer could be increased significantly by reducing the agitation speed or adding Vc, indicating that the enhancement of 2,3-BDL is closely associated with the adjustment of NADH/NAD(+) ratio. Especially, Vc addition elevated the 2,3-BDL titer from 43.66 g L(-1) to 71.71 g L(-1) within 54 h under fed-batch fermentation. This is the highest titer of 2,3-BDL so far reported for P. polymyxa from glucose fermentation. This work provides a new strategy to improve 2,3-BDL production and helps us to understand the responses of P. polymyxa to extracellular oxidoreduction potential.

Topics: Ascorbic Acid; Batch Cell Culture Techniques; Borohydrides; Butylene Glycols; Extracellular Space; Fermentation; Intracellular Space; Molecular Sequence Data; NAD; Oxidation-Reduction; Oxygen; Paenibacillus; Temperature

A novel synthetic approach was developed for creating versatile hollow Au nanostructures by stepwise reductions of Au(III) upon the use of cationic gemini surfactant hexamethylene-1,6-bis(dodecyl dimethylammonium bromide) (C12C6C12Br2) as a template agent. It was observed that the Au(I) ions obtained from the reduction of Au(III) by ascorbic acid can assist the gemini surfactant to form vesicles, capsule-like, and tube-like aggregates that subsequently act as soft templates for hollow Au nanostructures upon further reduction of Au(I) to Au(0) by NaBH4. It was demonstrated that the combination of C12C6C12Br2 and Au(I) plays a key role in regulating the structure of the hollow precursors not only because C12C6C12Br2 has a stronger aggregation ability in comparison with its single chain counterpart but also because the electrostatic repulsion between head groups of C12C6C12Br2 is greatly weakened after Au(III) is converted to Au(I), which is in favor of the construction of vesicles, capsule-like, and tube-like aggregates. Compared with solid Au nanospheres, the resultant hollow nanostructures exhibit enhanced electrocatalytic activities in methanol oxidation, following the order of elongated nanocapsule > nanocapsule > nanosphere. Benefiting from balanced interactions between the gemini surfactant and Au(I), this soft-template method may present a facile and versatile approach for the controlled synthesis of Au nanostructures potentially useful for fuel cells and other Au nanodevices.

Topics: Alkenes; Ascorbic Acid; Borohydrides; Cations; Electrochemical Techniques; Gold; Methanol; Microscopy, Electron, Transmission; Nanostructures; Nanotechnology; Oxidation-Reduction; Quaternary Ammonium Compounds; Surface-Active Agents

Cysteine and triethanolamine capped CdTe nanoparticles have been synthesized using a simple aqueous solution based method. This method involves the reaction of tellurium powder with sodium borohydride (NaBH(4)) in water to produce telluride ions (Te(2-)), followed by the simultaneous addition of an aqueous solution of cadmium chloride or other cadmium source (acetate, carbonate and nitrate) and solution of L-cysteine ethyl ester hydrochloride or triethanolamine. The effect of capping agent on the size, structure and morphology of the as-synthesized nanoparticles was investigated. The particles were characterized using optical spectroscopy, transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy.

Topics: Ascorbic Acid; Borohydrides; Cadmium; Cadmium Compounds; Cysteine; Ethanolamines; Indicators and Reagents; Luminescence; Microscopy, Electron, Transmission; Nanoparticles; Particle Size; Spectrophotometry, Ultraviolet; Spectroscopy, Fourier Transform Infrared; Tellurium; X-Ray Diffraction

A method for estimating the release of contaminants from contaminated sites under reducing conditions is proposed. The ability of two chemical reducing agents, sodium ascorbate and sodium borohydride, to produce different redox environments in a gold mining soil contaminated with arsenic was investigated. Liquid-solid partitioning experiments were carried out in the presence of each of the reducing agents at different pH conditions. Both the effect of varying concentrations of the reducing agent and the effect of varying pH in the presence of a constant concentration of the reducing agent were studied. Concentrations of sodium ascorbate ranging from 0.0075 to 0.046 mol L(-1) and concentrations of sodium borohydride ranging from 0.0075 to 0.075 mol L(-1) were examined. The addition of varying concentrations of sodium borohydride provided greater reducing conditions (ranging from -500 to +140 mV versus NHE) than that obtained using sodium ascorbate (ranging from -7 to +345 mV versus NHE). The solubilization of arsenic and iron was significantly increased by the addition of sodium ascorbate for all concentrations examined and pH tested, compared to that obtained under oxidizing conditions (as much as three orders of magnitude and four orders of magnitude, respectively, for the addition of 0.046 mol L(-1) of sodium ascorbate). In contrast, the alkaline and highly reduced soil conditions obtained with sodium borohydride lead to a lower effect on arsenic solubilization (as much as one order of magnitude for pH values between ca. 7 and 10 and no effect for pH values between ca. 10 and 12) and no effect on iron solubilization for all concentrations examined and pH tested. At similar ORP-pH conditions the results of extraction for arsenic and iron were different for the two reagents used.

Topics: Arsenic; Ascorbic Acid; Borohydrides; Hazardous Waste; Hydrogen-Ion Concentration; Kinetics; Mining; Oxidation-Reduction; Soil Pollutants

The toxicity of the beta-amyloid (Abeta) peptide of Alzheimer's disease may relate to its polymerisation state (i.e. fibril content). We have shown previously that plasma lipoproteins, particularly when oxidised, greatly enhance Abeta polymerisation. In the present study the nature of the interactions between both native and oxidised lipoproteins and Abeta1-40 was investigated employing various chemical treatments. The addition of ascorbic acid or the vitamin E analogue, trolox, to lipoprotein/Abeta coincubations failed to inhibit Abeta fibrillogenesis, as did the treatment of lipoproteins with the aldehyde reductant, sodium borohydride. The putative lipid peroxide-derived aldehyde scavenger, aminoguanidine, however, inhibited Abeta-oxidised lipoprotein-potentiated polymerisation, but in a manner consistent with an antioxidant action for the drug. Lipoprotein treatment with the reactive aldehyde 4-hydroxy-2-trans-nonenal enhanced Abeta polymerisation in a concentration-dependent fashion. Incubation of Abeta with lipoprotein fractions from which the apoprotein components had been removed resulted in extents of polymerisation comparable to those observed with Abeta alone. These data indicate that the apoprotein components of plasma lipoproteins play a key role in promoting Abeta polymerisation, possibly via interactions with aldehydes.

Topics: Aldehydes; Alzheimer Disease; Amyloid beta-Peptides; Antioxidants; Apolipoproteins; Ascorbic Acid; Biopolymers; Borohydrides; Chromans; Guanidines; Humans; Kinetics; Lipoproteins; Oxidation-Reduction; Peptide Fragments

It has been proposed that plant cell-wall polysaccharides are subject in vivo to non-enzymic scission mediated by hydroxyl radicals (-*OH). In the present study, xyloglucan was subjected in vitro to partial, non-enzymic scission by treatment with ascorbate plus H(2)O(2), which together generate -*OH. The partially degraded xyloglucan appeared to contain ester bonds within the backbone, as indicated by an irreversible decrease in viscosity upon alkaline hydrolysis. Aldehyde and/or ketone groups were also introduced into the polysaccharide by -*OH-attack, as indicated by staining with aniline hydrogen-phthalate and by reaction with NaB(3)H(4). The introduction of ester and oxo groups supports the proposed sequence of reactions: (a) -*OH-mediated H-abstraction to produce a carbon-centred carbohydrate radical; (b) reaction of the latter with O(2); and (c) elimination of a hydroperoxyl radical (HO(2)*-). When the partially degraded xyloglucan was reduced with NaB(3)H(4) followed by acid hydrolysis, several 3H-aldoses were detected ([3H]galactose, [3H]xylose, [3H]glucose, [3H]ribose and probably [3H]mannose), in addition to unidentified 3H-products (probably including anhydroaldoses). 3H-Alditols were undetectable, showing that few or no conventional reducing termini were introduced. Digestion of the NaB(3)H(4)-reduced, partially degraded xyloglucan with Driselase released 25 times more [3H]Xyl-alpha-(1-->6)-Glc than Xyl-alpha-(1-->6)-[3H]Glc, suggesting that the xylose side-chains of the xyloglucan had been more heavily attacked by -*OH than the glucose residues of the backbone. The radioactive xyloglucan was readily digested by cellulase, yielding 3H-products in the hepta- to nonasaccharide range. A fingerprinting strategy for identifying -*OH-attacked xyloglucan in plant cell walls is proposed.

Topics: Ascorbic Acid; Borohydrides; Carbohydrate Conformation; Carbohydrate Sequence; Fabaceae; Galactose; Glucans; Glucose; Hydrogen Peroxide; Hydroxyl Radical; Mannose; Molecular Sequence Data; Oligodeoxyribonucleotides; Plants, Medicinal; Polysaccharides; Ribose; Seeds; Tritium; Xylans; Xylose

Cholesterol and alpha-tocopherol oxidations were studied in brain subcellular fractions isolated from cerebral hemispheres of 4-month-old, male Fischer 344 rats. The fractions were suspended in buffered media (pH 7.4, 37 degrees C0 and oxidized by adding (i) ferrous iron (Fe2+) with or without ascorbate or (ii) peroxynitrite (an endogenous oxidant produced by the reaction of superoxide and nitric oxide). Treatment of subcellular fractions with Fe2+ in the presence or absence of ascorbate produced primarily 7-keto- and 7-hydroxy-cholesterols and small amounts of 5 alpha, 6 alpha-epoxycholesterol. Since brain contains high levels of ascorbate, and release of iron could result in oxysterol formation. Peroxynitrite oxidized alpha-tocopherol but not cholesterol. Hence, the toxicity of peroxynitrite or nitric oxide could not be due to cytotoxic oxysterols. When synaptosomes were incubated for 5 min in the presence of 0.5 to 2 microM Fe2+ and ascorbate, alpha-tocopherol was oxidized while cholesterol remained unchanged. Thus, alpha-tocopherol is functioning as an antioxidant, protecting cholesterol. Diethylenetriaminepentaacetic acid blocked production of oxysterols, whereas citrate, ADP and EDTA did not. A significant percentage of mitochondrial cholesterol was oxidized by treatment with Fe2+ and ascorbate. Hence, mitochondrial membrane properties dependent on cholesterol could be particularly susceptible to oxidation. The oxysterols formed were retained within the membranes of synaptosomes and mitochondria. The 7-oxysterols produced are known to be inhibitors of membrane enzymes and also can modify membrane permeability. Hence, oxysterols may plan an important role in brain tissue damage during oxidative stress.

Topics: Animals; Antioxidants; Ascorbic Acid; Borohydrides; Brain; Chelating Agents; Cholesterol; Chromatography, Gas; Ferrous Compounds; Male; Mitochondria; Nitrates; Oxidation-Reduction; Oxidative Stress; Rats; Rats, Inbred F344; Synaptosomes; Vitamin E

Treatment of the porcine intestinal brush-border membranes with 100 microM ascorbic acid and 10 microM Fe2+ in the presence of various concentrations of tert-butyl hydroperoxide (t-BuOOH) resulted in a marked fluorescence development at 430 nm, depending on the hydroperoxide concentration. This fluorescence formation was closely related to lipid peroxidation of the membranes as assessed by formation of conjugated diene. However there is no linear relation between thiobarbituric acid-reactive substances (TBARS) and fluorescence formation. On the other hand, fluorescence formation in the membranes by treatment with ascorbic acid/Fe2+ or t-BuOOH alone was negligible. The results with antioxidants and radical scavengers suggest that ascorbic acid/Fe2+/t-BuOOH-induced lipid peroxidation of the membranes is mainly due to t-butoxyl and/or t-butyl peroxy radicals. Most TBARS produced during the peroxidation reaction were released from the membranes, but fluorescent products remained in the membrane components. The fluorescence properties of products formed by lipid peroxidation of the membranes were compared with those of products derived from the interaction of malondialdehyde (MDA) or acetaldehyde with the membranes. The fluorescence products in the acetaldehyde-modified membranes also exhibited the emission maximum at 430 nm, while the emission maximum of MDA-modified membranes was 470 nm. The fluorescence intensity of MDA-modified membranes was markedly decreased by treatment with 10 mM NaBH4 but that of the peroxidized or acetaldehyde-modified membranes was enhanced by about two-fold with the treatment. In addition, a pH dependence profile revealed that the fluorescence intensity of the peroxidized or acetaldehyde-modified membranes decreases with increasing pH of the medium, whereas that of MDA-modified ones did not change over the pH range from 5.4 to 8.0. On the basis of these results, the fluorescence properties of products formed in the intestinal brush-border membranes by lipid peroxidation are discussed.

Topics: Animals; Ascorbic Acid; Borohydrides; Hydrogen-Ion Concentration; Intestinal Mucosa; Intestines; Lipid Peroxidation; Malondialdehyde; Microvilli; Peroxides; Spectrometry, Fluorescence; Swine; tert-Butylhydroperoxide; Thiobarbiturates

The reducing effect of ascorbic acid and of borohydride upon ferrihaemoglobin present in native and chemically modified human and bovine stroma-free hemoglobins was investigated. Ferrihaemoglobin which had been freshly prepared from oxyhaemoglobin by treatment with potassium ferricyanate was fully reduced to ferrohaemoglobin. Full reduction of ferrihaemoglobin, however, could not be achieved with those haemoglobin samples which had a partially deteriorated conformation due to long time storage or chemical modification.

Topics: Animals; Ascorbic Acid; Borohydrides; Cattle; Hemoglobins; Humans; Infusions, Intravenous; Methemoglobin; Oxidation-Reduction; Solutions; Spectrophotometry, Atomic; Time Factors