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Fenton System (fenton + system)
Selected AbstractsEthanol Can Modify the Effects of Certain Free Radical-Generating Systems on AstrocytesALCOHOLISM, Issue 4 2004B. Gonthier Abstract: The central nervous system is vulnerable to oxidative stress, especially when a toxicant can modify the physiological balance between anti- and pro-oxidant mechanisms. Among brain cells, astrocytes seem less vulnerable than neurons, but their impairment can dramatically affect neurons because of their protective role toward neurons. Ethanol is able to stimulate the formation of reactive oxygen species and modify the activity of most of the antioxidant agents. However, ethanol can react with the OH· radical to form the ,-hydroxyethyl radical, which is considered to be less toxic. Ethanol also can stimulate H2O2 degradation through catalase activation. This study, therefore, sought to determine whether ethanol affected the sensitivity of astrocytes exposed to various free radical-generating systems. The cellular impact of such exposure was assessed by assays exploring cytotoxicity (i.e., NR (neutral red) and MMT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetiazolium bromide) reduction assays) and genotoxicity (comet assay) induced by these treatments. DNA alterations were evaluated by single-cell gel electrophoresis (comet assay), considered a precocious biomarker of intracellular alterations. After concomitant exposure to H2O2 and ethanol, the viability of astrocytes decreased significantly whereas the mean percentage of DNA in the tail increased, reflecting DNA damage (H2O2 was either directly added to the culture medium or endogenously produced from menadione). Ethanol also reduced the loss of viability and DNA alterations after exposure to OH· radicals produced by a Fenton system. The exposure to a xanthine/xanthine oxidase system had the same effect. [source] A fluorimetric method for the determination of trace pentachlorophenol, based on its inhibitory effect on the redox reaction between the improved Fenton reagent and rhodamine BLUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 5 2007Huiqin Guo Abstract A sensitive fluorimetric method is presented and discussed for the determination of pentachlorophenol in aqueous solutions. This method is based on the inhibitory effect of pentachlorophenol on the reaction of conventional Fenton [Fe(III) + H2O2] reagent with rhodamine B in the medium of perchloric acid, which results in the fluorescence quenching of rhodamine B. It was further found that the sensitivity for the determination was improved significantly when the molecular ligand EDTA was added. This improved system was therefore presented for the determination of pentachlorophenol. The characteristics of the excitation and emission spectra, optimization of the experimental conditions, the stability of the system and the influence of foreign matter have all been investigated. Under optimal conditions, the linear range for the determination of pentachlorophenol is 12,480 ng/mL with a 3, limit of detection of 0.96 ng/mL. Compared with the conventional Fenton system, the improved system shows obvious advantages in both sensitivity and selectivity. By combination with the pretreatment of samples using ion exchange resins and XDA-1 absorption resin, the improved Fenton method was used for the first time for the determination of pentachlorophenol in synthetic samples and natural water samples, and satisfactory results, in agreement with those of the HPLC method, were achieved. The possible mechanism of the reactions has also been discussed. Copyright © 2007 John Wiley & Sons, Ltd. [source] Innovative membrane based process for the selective oxidation of light alkanes assisted by the Fenton systemASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2010C. Espro Abstract Selective oxidation of light alkanes under mild conditions (temp, 80,120 °C; pressure, 140 kPa) mediated by Fe2+/H2O2 Fenton system on Nafion based composite membranes is studied in a multifunctional three phase catalytic membrane reactor (3PCMR). The role of textural properties and acid functionality on the catalytic performance of the Nafion composite membranes is outlined. The features of the multifunctional 3PCMR, enabling reaction along with product separation and recovery, are discussed. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Potential antioxidant activity of celecoxib and amtolmetin guacyl: in vitro studiesAUTONOMIC & AUTACOID PHARMACOLOGY, Issue 1 2007M. Kirkova Summary 1,In vitro studies of the potential antioxidant activity of the selective cyclo-oxygenase-2 inhibitor celecoxib and the non-steroid anti-inflammatory drug amtolmetin guacyl (AMG) were carried out. The study included experiments on the ability of these drugs to affect some indices of the oxidative stress [lipid peroxidation (LP), activity of antioxidant enzymes, glutathione (GSH) level] in rat stomach and colon mucosa and in liver. 2,Celecoxib and AMG did not change the activity of the enzymes GSH-peroxidase, oxidased glutathione (GSSG)-reductase and glucose-6-phosphate-dehydrogenase, as well as the GSH level in all tissue preparations. An increased superoxide dismutase (SOD) activity and a tendency to a decreased Fe/ascorbic acid-induced LP in stomach and colon mucosa were found, but only in the presence of AMG. 3,In the liver, both celecoxib and AMG decreased spontaneous and Fe/ascorbic acid-induced LP. SOD activity was enhanced only in the presence of AMG. 4,Experiments aimed at studying celecoxib and AMG in free oxygen radical-generating systems were also carried out. AMG and tolmetin (the main metabolite of AMG) inhibited OH, -provoked deoxyribose degradation in a Fenton system. Celecoxib had no effect on free radicals when tested in the same system. 5,In conclusion, the results of the present in vitro studies suggest that AMG and celecoxib possess antioxidant and metal-chelating abilities, which might contribute to their beneficial effects. [source] Analysis of oxidation process of cholecystokinin octapeptide with reactive oxygen species by high-performance liquid chromatography and subsequent electrospray ionization mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 2 2010Hideaki Ichiba Abstract The C -terminal octapeptide of cholecystokinin (CCK8) includes some easily oxidizable amino acids. The oxidation of CCK8 by reactive oxygen species (ROS) such as hydrogen peroxide (H2O2) and hydroxyl radicals (OH,) was investigated using reversed-phase high performance liquid chromatography (RP-HPLC) and subsequent electrospray ionization mass spectrometry. The mechanism of oxidation of CCK8 in the H2O2 system differed from that of CCK8 in the Fenton system, in which OH, are produced. In the H2O2 system, 28Met and 31Met were oxidized to methionine sulfoxide, and no further oxidation or degradation/hydrolysis occurred. On the other hand, in the Fenton system, 28Met and 31Met residues were oxidized to methionine sulfone via the formation of methionine sulfoxide. In addition, the oxidized product was observed at the Trp residue but not at the Tyr residue, and small peptide fragments from CCK8 were observed in the Fenton system. From these results, it was concluded that 28Met and 31Met residues of CCK8 are susceptible to oxidation by ROS. Copyright © 2009 John Wiley & Sons, Ltd. 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