ascorbic-acid and aniline

Nitrobenzene (NB) is recalcitrant to microbial biodegradation due to the electron-deficient character of the nitro group (NO

Topics: Acetanilides; Aniline Compounds; Ascorbic Acid; Biodegradation, Environmental; Feasibility Studies; Kinetics; Nitrobenzenes; Oleic Acids; Peptones; Soil; Soil Pollutants

Ascorbic acid (vitamin C) has been used as a radical initiator in a metal-free direct C-H arylation of (hetero)arenes. Starting from an aniline, the corresponding arenediazonium ion is generated in situ and immediately reduced by vitamin C to an aryl radical that undergoes a homolytic aromatic substitution with a (hetero)arene. Notably, neither heating nor irradiation is required. This procedure is mild, operationally simple, and constitutes a greener approach to arylation.

Topics: Aniline Compounds; Ascorbic Acid; Benzene Derivatives; Carbon; Free Radicals; Green Chemistry Technology; Hydrogen

Self-doped poly(aniline)s as electrode coatings to catalyze ascorbate oxidation are revisited in this article. Sulfonated poly(aniline) (SPAN) was deposited on glassy carbon electrodes as a copolymer of aniline and its sulfonated derivative, 2-aminobenzenesulfonic acid (2-ABSA). The resulting deposits are reproducible and show good stability and electroactivity at pH>7, enabling studies at typical physiological pH values. Calibration curves were obtained using a rotating disc electrode at a sampling potential of 0.2V, displaying linear dependence in the region 0-20mM ascorbate. A kinetic model based on the Michaelis-Menten reaction mechanism, previously validated for poly(aniline) composites, was used to analyse the form of the calibration curve leading to values of the effective reaction constants K(ME) and k'(ME). New calibration curves constructed for different sampling potentials were used to elucidate the rate limiting step at saturated kinetics. Rotating disc voltammetry performed at increasing pH (from pH 2 to 9) showed a dramatic decrease in the limiting current, without any evidence for a change in the reaction mechanism.

Topics: Alkanesulfonates; Aniline Compounds; Ascorbic Acid; Calibration; Carbon; Catalysis; Electrochemistry; Electrodes; Hydrogen-Ion Concentration; Kinetics; Oxidation-Reduction; Polymers

A detailed kinetic study is provided for the oxidation of ascorbate at poly(aniline)-poly(styrene sulfonate) coated microelectrodes. Flat films with a low degree of polymer spillover and a thickness much lower than the microelectrode radius were produced by controlled potentiodynamic electrodeposition. The currents for ascorbate oxidation are found to be independent of the polymer thickness, indicating that the reaction occurs at the outer surface of the polymer film. At low ascorbate concentrations, below around 40 mM, the currents are found to be mass transport limited. At higher ascorbate concentrations the currents became kinetically limited. The experimental data for measurements at a range of potentials are fitted to a consistent kinetic model and the results summarized in a case diagram. The results obtained for the poly(aniline)-(polystyrene sulfonate) coated microelectrode are compared to those for a poly(aniline)-poly(vinyl sulfonate) coated microelectrode and to the results of an earlier study of the reaction at poly(aniline)-poly(vinyl sulfonate) coated rotating disc electrodes. For poly(aniline)-poly(styrene sulfonate) the oxidation of ascorbate is found to proceed by one electron reaction whereas for poly(aniline)-poly(vinyl sulfonate) the reaction is found to be a two electron oxidation.

Topics: Aniline Compounds; Ascorbic Acid; Kinetics; Microelectrodes; Microscopy, Electron, Scanning; Oxidation-Reduction; Platinum; Polymers; Polystyrenes

A poly(aniline-co-m-ferrocenylaniline) was successfully synthesized on a glassy carbon electrode (GCE) by electrochemical copolymerization using a scan potential range from -0.3 to +0.9 V (vs. Ag/AgCl) in 0.5 M H2SO4 containing 30% acetonitrile (ACN), 0.1 M aniline (Ani) and 0.005 M m-ferrocenyaniline (m-FcAni). The field emission scanning electron microscope (FESEM) and electrochemical methods were used to characterize the poly(Ani-co-m-FcAni) modified electrode. The poly(Ani-co-m-FcAni)/GCE exhibited excellent electrocatalytic oxidation of ascorbic acid (AA) in citrate buffer solution (CBS, pH 5.0). The anodic peak potential of AA was shifted from +0.55 V at the bare GCE to +0.25 V at the poly(Ani-co-m-FcAni)/GCE with higher current responses than those seen on the bare GCE. The scan number at the 10th cycle was selected as the maximum scan cycle in electrochemical polymerization. The limit of detection (LOD) was estimated to be 2.0 μM based on the signal-to-noise ratio (S/N = 3). The amperometric responses demonstrated an excellent selectivity for AA determination over glucose (Glu) and dopamine (DA).

Topics: Aniline Compounds; Ascorbic Acid; Catalysis; Dopamine; Electrochemical Techniques; Electrodes; Electrolysis; Ferrous Compounds; Fructose; Galactose; Glucose; Hydrogen-Ion Concentration; Metallocenes; Microscopy, Electron, Scanning; Oxidation-Reduction; Polymers; Sodium Chloride; Sucrose; Surface Properties

The formation of aniline from sodium salt of 6-hydroxy-5-(phenylazo)-2-naphthalenesulphonic acid (SS-AN, C.I. 15970, Orange RN), a subsidiary colour in the Japanese colour additive Food Yellow No. 5 (Y-5, C.I. 15985, Sunset Yellow FCF), was investigated in the artificial gastric fluid (AGF) and in the artificial intestinal fluid (AIF) as prescribed in the degradation test in the Japanese Pharmacopoeia (1996). Aniline concentrations of 0.3-6.8 micrograms/ml were found in 0.1% SS-AN solutions with 0.1-5.0% ascorbic acid or erythorbic acid after 24 h at 37 degrees C. This simulates a mixture of dye and ascorbic acid that might be ingested. The amount of aniline generated depended upon the temperature in these systems. In systems to which sucrose had been added, an increase in the amount of aniline generated was observed. However, no aniline generation was observed in the 0.1% SS-AN solutions in the AGF or AIF at 37 degrees C for 24 h. Furthermore, the generation of aniline was not seen in AGF and AIF at higher temperatures in the range of 37-80 degrees C. It was not generated by the degradation of SS-AN in the presence of digestive enzymes.

Topics: Aniline Compounds; Ascorbic Acid; Azo Compounds; Chromatography, High Pressure Liquid; Food Coloring Agents; Temperature

For the investigation of luminol (LM)-and lucigenin (LC)-amplified chemiluminescence (CL) in rat liver microsomes using both a liquid-scintillation counter (LKB/Wallac 1219 Rackbeta) and a Berthold luminometer (AutoLumat LB 953) optimal incubation mixtures and conditions and basic kinetics have been established. Whereas calibration curves for both LM- and LC-CL are performed with hydrogenperoxide (LC quantum yield is 6.25 fold higher as that of LM), distinct differences were revealed with microsomes, indicating that different reactive oxygen species (ROS) are determined: Both LM- and LC-CL follow the kinetics of enzymatic reactions in terms of dependence on protein and NADPH or NADH concentration, time course, temperature etc., but with differences. LM-CL does not work without addition of Fe2+, whereas LC-CL does. Both copper ions and copper bound in a complex abolish CL, LC-CL being much more sensitive. Isolated cytochrome P-450 (P450) and NADPH P450 reductase from liver of pheno-barbital treated rats alone proved to be inactive in LM-and LC-CL production, whereas te combination 1:1 without and with addition of lipid was highly active in both LM-and LC-CL. Ascorbic acid and glutathione as scavengers diminish both LM- and LC-CL in concentrations higher then 10(5). Dimethyl-sulfoxide (DMSO) was ineffective in LM-CL up to concentrations of 0.2 M, the very high concentration of 2 M diminished LM-CL only to 1/3. LC-CL was diminished starting at concentrations of 100 mM and at 2 M only 10% of maximum LC-CL was observed. The trap substance N-t-butyl-a-phenylnitrone (BNP) also diminished LC-CL more effectively than LM-CL. Clearcut differences were revealed by the addition of catalase and superoxide dismutase: both enzymes diminished LM-CL only, without any influence on LC-CL. Hexobarbital, a potent uncoupler of P450, enhances LM-CL fivefold, whereas LC-CL is barely influenced. Aniline (without uncoupling capability) decreased both LM-and LC-CL increasingly with increasing concentrations. Therefore the conclusion is drawn that LM-CL measures in liver microsomes predominantly superoxide anion radicals, whereas LC-CL is mainly a measure for microsomal hydroxyl radical formation or of reactive organic radicals. With microsomes of phenobarbital and beta-naphthoflavone treated rats CL was much higher but in principle the same kinetic characteristics could be shown. All results on microsomes were obtained uniformly with the liquid scintillation counter and the Berthold

Topics: Acridines; Aniline Compounds; Animals; Ascorbic Acid; Catalase; Copper; Cyclic N-Oxides; Cytochrome P-450 Enzyme System; Dimethyl Sulfoxide; Glutathione; Hexobarbital; Iron; Kinetics; Luminescent Measurements; Luminol; Male; Microsomes, Liver; NADPH Dehydrogenase; Nitrogen Oxides; Proteins; Rats; Rats, Wistar; Superoxide Dismutase; Temperature; Time Factors

The mechanism of aromatic hydroxylation of aniline and phenol derivatives in a H2O2-driven microperoxidase-8(MP8)-catalyzed reaction was investigated. It was shown that the reaction was not inhibited by the addition of scavengers of superoxide anion or hydroxyl radicals, which demonstrates that the reaction mechanism differs from that of the aromatic hydroxylation catalyzed by a horseradish peroxidase/ dihydroxyfumarate system. Additional experiments with 18O-labelled H2 18O2 demonstrated that the oxygen incorporated into aniline to give 4-aminophenol originates from H2O2. Furthermore, it was found that the addition of ascorbic acid efficiently blocks all peroxidase-type reactions that can be catalyzed by the MP8/H2O2 system, but does not inhibit the aromatic hydroxylation of aniline and phenol derivatives. Together, these observations exclude reaction mechanisms for the aromatic hydroxylation that proceed through peroxidase-type mechanisms in which the oxygen incorporated into the substrate originates from O2 or H2O. The mechanism instead seems to proceed by an initial attack of the high-valent iron-oxo intermediate of MP8 on the pi-electrons of the aromatic ring of the substrate leading to product formation by a cytochrome-P-450-type of sigma-O-addition or oxygen-rebound mechanism. This implies that MP8, which has a histidyl and not a cysteinate fifth axial ligand, is able to react by a cytochrome-P-450-like oxygen-transfer reaction mechanism.

Topics: Aminophenols; Aniline Compounds; Animals; Ascorbic Acid; Cytochrome c Group; Cytochrome P-450 Enzyme System; Gas Chromatography-Mass Spectrometry; Horses; Hydrogen Peroxide; Hydrogen-Ion Concentration; Hydroxyl Radical; Hydroxylation; Kinetics; Magnetic Resonance Spectroscopy; Mitochondria, Heart; Oxygen Isotopes; Peroxidases; Superoxides

Effects of dietary ethanol on ascorbic acid and lipid metabolism, and liver drug-metabolizing enzymes in rats fed a semi-purified diet containing a powdered ethanol preparation (30 cal% in the diet) were studied. Administration of ethanol increased urinary ascorbic acid excretion (p less than 0.001) and ascorbic acid level in the liver (p less than 0.001) and the spleen (p less than 0.01). The activity of hepatic aniline hydroxylase was increased (p less than 0.05) by ethanol feeding but that of aminopyrine N-demethylase was not. Increases of serum total and high-density-lipoprotein (HDL) cholesterol level, commonly observed by the administration of xenobiotics, were not observed. These results showed ethanol possessed rather similar properties to xenobiotics such as polychlorinated biphenyls (PCB) or 1,1,1-trichloro-2,2-bis(p-chlorophenyl)-ethane (DDT) in some metabolic changes. In this study, no accumulation of lipid in the liver was observed.

Topics: Aminopyrine N-Demethylase; Aniline Compounds; Animals; Ascorbic Acid; Cholesterol; Diet; Ethanol; Hydrolases; Lipid Metabolism; Liver; Male; Rats; Rats, Inbred Strains

The iron-catalysed production of hydroxyl radicals, by rat liver microsomes (microsomal fractions), assessed by the oxidation of substrate scavengers and ethanol, displayed a biphasic response to the concentration of O2 (varied from 3 to 70%), reaching a maximal value with 20% O2. The decreased rates of hydroxyl-radical generation at lower O2 concentrations correlates with lower rates of production of H2O2, the precursor of hydroxyl radical, whereas the decreased rates at elevated O2 concentrations correlate with lower rates (relative to 20% O2) of activity of NADPH-cytochrome P-450 reductase, which reduces iron and is responsible for redox cycling of iron by the microsomes. The oxidation of aniline or aminopyrine and the cytochrome P-450/oxygen-radical-independent oxidation of ethanol also displayed a biphasic response to the concentration of O2, reaching a maximum at 20% O2, which correlates with the dithionite-reducible CO-binding spectra of cytochrome P-450. Microsomal lipid peroxidation increased as the concentration of O2 was raised from 3 to 7 to 20% O2, and then began to level off. This different pattern of malondialdehyde generation compared with hydroxyl-radical production probably reflects the lack of a role for hydroxyl radical in microsomal lipid peroxidation. These results point to the complex role for O2 in microsomal generation of oxygen radicals, which is due in part to the critical necessity for maintaining the redox state of autoxidizable components of the reaction system.

Topics: 1-Butanol; Aminopyrine; Aniline Compounds; Animals; Ascorbic Acid; Butanols; Cytochrome P-450 Enzyme System; Ethanol; Free Radicals; Hydrogen Peroxide; Male; Microsomes, Liver; Oxidation-Reduction; Oxygen; Rats; Rats, Inbred Strains; Spectrophotometry

Topics: Aniline Compounds; Ascorbic Acid; Cytochrome P-450 Enzyme System; Fumarates; Hemoglobins; Humans; Hydroxylation; Kinetics; Methemoglobin; NAD; Oxyhemoglobins; Riboflavin

Topics: Acetanilides; Aniline Compounds; Ascorbic Acid; Esterases; Glutathione; Liver; NAD; NADP; Phenols; Phenylhydrazines; Research; Sulfites; Ultraviolet Rays

Topics: Aniline Compounds; Ascorbic Acid; Humans; Vitamins

Topics: Aniline Compounds; Ascorbic Acid; Humans; Methylene Blue; Vitamins

Topics: Aniline Compounds; Ascorbic Acid; Coloring Agents; Phenylenediamines; Psychotic Disorders; Schizophrenia

Topics: Administration, Oral; Aniline Compounds; Ascorbic Acid; Chalcones; Coloring Agents; Flavonoids; Hemophilia A; Hesperidin; Hypoprothrombinemias; Leukemia; Prothrombin; Purpura; Purpura, Thrombocytopenic; Tolonium Chloride; Vitamins

Topics: Acetanilides; Analgesics; Aniline Compounds; Antipyrine; Ascorbic Acid; Coloring Agents; Hydroxylation

Topics: Aniline Compounds; Ascorbic Acid; Chromium; Coloring Agents; Dermatitis; Dermatitis, Contact; Humans; Turpentine; Vitamins