ascorbic-acid and catechol

The present study aims to investigate the substrate (4-methyl catechol and catechol) specificity and inhibition mechanisms (l-ascorbic acid, citric acid, and l-cysteine) of the tyrosinase enzyme (TYR), which is held responsible for browning in foods and hyperpigmentation in the human skin, through kinetic and molecular docking studies. During the experimental studies, the diphenolase activities of TYR were determined, following which the inhibitory effects of the inhibitors upon the diphenolase activities of TYR. The inhibition types were determined as competitively for l-ascorbic acid and citric acid and noncompetitive for l-cysteine. The kinetic results showed that the substrate specificity was better for catechol while l-cysteine showed the best inhibition profile. As for the

Topics: Agaricales; Agaricus; Ascorbic Acid; Catechols; Citric Acid; Cysteine; Enzyme Inhibitors; Guaiacol; Humans; Kinetics; Molecular Docking Simulation; Monophenol Monooxygenase

Topics: Ascorbic Acid; Catechol Oxidase; Catechols; Foeniculum; Fruit; Hydrogen-Ion Concentration; Kinetics; Molecular Weight; Oxidation-Reduction; Pyrogallol; Seeds; Substrate Specificity; Sulfites; Temperature

Green colored mononuclear copper(II) complexes viz. [Cu(L)(bpy)](ClO

Topics: Ascorbic Acid; Benzylamines; Catalysis; Catechols; Coordination Complexes; Copper; Molecular Structure; Oxidation-Reduction; Oxidoreductases

In this work, we present a new catechol amperometric biosensor fabricated on the basis of naturally available enzymes in common mushrooms. The biosensor response mechanism comprises the reduction of the quinone exclusively produced in the oxidation of the catechol present in the sample, which is catalyzed by tyrosinase enzyme. The new catechol biosensor has demonstrated excellent analytical performance at increasing catechol concentrations in the sample solution, which includes superior reproducibility for several electrodes and long-term stability. On top of that, the biosensing element used in the fabrication is a sustainable material, of low-cost and presents an excellent lifetime of years. Whether the catechol biosensor is operating in the presence of a compound influencing the reactions underlying the amperometric response (such as ascorbic, benzoic, gallic and kojic acids), this serves as an analytical platform to detect these compounds in real samples. Particularly, we introduce herein for the first time different treatments to process the current signal of the biosensor pursuing the linearity needed for the analytical application in real samples. In this sense, the catechol biosensor has been successfully applied to the detection of benzoic, gallic and kojic acids in juices, teas and cosmetic products, respectively.

Topics: Agaricales; Ascorbic Acid; Benzoic Acid; Biosensing Techniques; Catechols; Electrochemistry; Gallic Acid; Monophenol Monooxygenase; Pyrones

The development of minimally invasive surgery has created a demand for ideal medical adhesives exhibiting biocompatibility, biodegradability, antimicrobial activity, and strong adhesion to tissues in wet environments. However, as clinically approved surgical tissue glues suffer from poor adhesion activation, limited adhesion strength, and toxicity, novel tissue glues are highly sought after. Herein, a mussel-inspired injectable hydrogel was prepared from catechol- and methacrylate-modified chitosan/gelatin and shown to exhibit biocompatibility, inherent antimicrobial activity, and good adhesion to wet tissues. Moreover, as this gel could be applied onto tissue surfaces and cured in situ within seconds of body contact by a biocompatible and multifunctional redox initiator (H

Topics: Animals; Anti-Bacterial Agents; Ascorbic Acid; Bivalvia; Body Temperature; Catechols; Chitosan; Gelatin; Hydrogels; Hydrogen Peroxide; Injections; Methacrylates; Mice; NIH 3T3 Cells; Pseudomonas aeruginosa; Rats, Sprague-Dawley; Staphylococcus aureus; Sutureless Surgical Procedures; Tissue Adhesives; Wound Healing; Wound Infection

Polyphenol oxidase from Granny Smith apples was purified and characterized in both its soluble form (sPPO) and its membrane-bound form (mPPO). Both forms were purified by temperature-induced phase partitioning, precipitation with ammonium sulfate, and ion exchange chromatography. The specific activity of mPPO was 19.17 times that of sPPO. The optimum pH and temperature for both forms were 7.0 and 35 °C when catechol was the substrate. The Michaelis constant and maximum reaction rate for sPPO were 34.1 mM and 500 U/mL/min, whereas those for mPPO were 53 mM and 10,000 U/mL/min, respectively. The enzymes exhibited diphenolase activity, and their affinity was highest for catechol (sPPO) and 4-methylcatechol (mPPO). Inhibitors of sPPO and mPPO included ascorbic acid, glutathione, and l-cysteine. However, ethylenediaminetetraacetic acid increased the activity of mPPO. Purified sPPO was dimeric with a molecular weight of 31 kDa, whereas mPPO was monomeric with an estimated molecular weight of 65 kDa.

Topics: Ascorbic Acid; Catechol Oxidase; Catechols; Cysteine; Edetic Acid; Fruit; Glutathione; Hydrogen-Ion Concentration; Malus; Molecular Weight; Plant Proteins; Substrate Specificity; Temperature

A fluorescent nanoprobe based on nitrogen-doped carbon dots (N-CDs) with green fluorescent emission have been fabricated through a facile one-step hydrothermal treatment using catechol and triethylene tetramine as precursors. The obtained N-CDs with excellent luminescent properties and superior biocompatibility have been applied for the development of a bifunctional sensor for the detection of Fe

Topics: Actinidia; Ascorbic Acid; Biosensing Techniques; Carbon; Catechols; Citrus sinensis; Drinking Water; Fluorescent Dyes; Fruit; Iron; Limit of Detection; Nanostructures; Nitrogen; Oxidation-Reduction; Quantum Dots; Spectrometry, Fluorescence; Trientine; Vitis

Open wounds and burns are prone to infection and there remains considerable interest in developing safe and effective mechanisms to confer antimicrobial activities to wound dressings. We report a biomimetic wound dressing for the in situ and sustained generation of reactive oxygen species (ROS). Specifically, we fabricate a catechol-modified chitosan film that mimics features of the melanin capsule generated during an insect immune response to infection. We use an electrochemical reverse engineering approach to demonstrate that this catechol-chitosan film possesses redox-activities and can be repeatedly oxidized and reduced. In vitro tests demonstrate that this film catalyzes the transfer of electrons from physiological reductant ascorbate to O

Topics: Animals; Anti-Bacterial Agents; Ascorbic Acid; Catechols; Cell Line, Tumor; Chitosan; Electroplating; Escherichia coli; Humans; Male; Mice, Inbred BALB C; Microscopy, Electron, Scanning; Oxidation-Reduction; Oxygen; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species; Staphylococcus aureus

In this paper, a facile and rapid fluorescence turn-on assay for fluorescent detection of ascorbic acid (AA) was developed by using the orange emission graphene quantum dots (GQDs). In the presence of horse radish peroxidase (HRP) and hydrogen peroxide (H

Topics: Ascorbic Acid; Benzoquinones; Biosensing Techniques; Catechols; Fluorescent Dyes; Graphite; Horseradish Peroxidase; Humans; Hydrogen Peroxide; Limit of Detection; Quantum Dots; Spectrometry, Fluorescence

Cape gooseberry (Physalis peruviana) is an exotic fruit highly valued, however it is a very rich source of polyphenol oxidase (PPO). In this study, Cape gooseberry PPO was isolated and biochemically characterized. The enzyme was extracted and purified using acetone and aqueous two-phase systems. The data indicated that PPO had the highest substrate affinity for chlorogenic acid, 4-methylcatechol and catechol. Chlorogenic acid was the most suitable substrate (Km=0.56±0.07 mM and Vmax=53.15±2.03 UPPO mL(-1) min(-1)). The optimal pH values were 5.5 for catechol and 4-methylcatechol and 5.0 for chlorogenic acid. Optimal temperatures were 40°C for catechol, 25°C for 4-methylcatechol and 20°C for chlorogenic acid. In inhibition tests, the most potent inhibitor was found to be ascorbic acid followed by L-cysteine and quercetin. This study shows possible treatments that can be implemented during the processing of Cape gooseberry fruits to prevent browning.

Topics: Ascorbic Acid; Catechol Oxidase; Catechols; Chlorogenic Acid; Cysteine; Enzyme Stability; Fruit; Molecular Weight; Physalis; Substrate Specificity; Temperature

Dietary polyphenols are markedly studied for their antioxidant activity. They also have a negative impact on nutrition whereby they interfere with iron absorption. Common dietary polyphenols include: catechins, flavonols, flavanols, flavones, anthocyanins, proanthocyanidins and phenolic acids. Ascorbic acid (AA) and Ethylenediaminetetraacetic acid (EDTA) are commonly used to counter act this reaction and increase iron bioavailability. This study was aimed at determining the effect of AA and EDTA on the catechol or galloyl iron binding ability of pure phenolics, coffee and tea. Phenolic concentrations of 40, 80, 610, 240, 320, 400, 520 and 900 μg/ml were tested against six levels of AA and EDTA. These effects were studied in detail using Multivariate Analysis of Variance (MANOVA) with the hypothesis that there would be one or more mean differences between the ratio of enhancer and the different concentrations of samples tested. AA was found to be more efficient than EDTA in a way that lesser quantity is required for completely overcoming negative iron binding effects of polyphenols and similar samples.

Topics: Ascorbic Acid; Catechols; Discriminant Analysis; Edetic Acid; Iron; Polyphenols

Polyaniline-iron oxide magnetic nanohybrid was synthesized and characterized using various spectroscopic, microstructural and electrochemical techniques. The smart integration of Fe3O4 nanoparticles within the polyaniline (PANI) matrix yielded a mesoporous nanohybrid (Fe3O4@PANI) with high surface area (94 m(2) g(-1)) and average pore width of 12.8 nm. Catechol is quasi-reversibly oxidized to o-quinone and reduced at the Fe3O4@PANI modified electrodes. The amperometric current response toward catechol was evaluated using the nanohybrid and the sensitivity and detection limit were found to be 312 μA μL(-1) and 0.2 nM, respectively. The results from electrochemical impedance spectroscopy (EIS) indicated that the increased solution resistance (Rs) was due to elevated adsorption of catechol on the modified electrodes. Photoluminescence spectra showed ligand-to-metal charge transfer (LMCT) between p-π orbitals of the phenolate oxygen in catechol and the d-σ* metal orbital of Fe3O4@PANI nanohybrid. Potential dependent spectroelectrochemical behavior of Fe3O4@PANI nanohybrid toward catechol was studied using UV/vis/NIR spectroscopy. The binding activity of the biomagnetic particles to catechol through Brownian relaxation was evident from AC susceptibility measurements. The proposed sensor was used for successful recovery of catechol in tap water samples.

Topics: Aniline Compounds; Ascorbic Acid; Catechols; Dielectric Spectroscopy; Dopamine; Electrochemical Techniques; Electrodes; Ferrosoferric Oxide; Magnetics; Metal Nanoparticles; Nanostructures; Porosity

This study develops a novel and high performance colorimetric probe for dopamine (DA) detection. Aqueous-phase gold nanoparticles (AuNPs) extracted with 4-(dimethylamino)pyridine (DMAP) from toluene solvent are used as the reaction probes. The original AuNPs of diameter around 13 nm separate into 2-5 nm sizes when dopamine (DA) is added, resulting in the color change of the AuNP solution from red to blackish green. Transmission electron microscopy (TEM) observations and dynamic light scattering (DLS) tests show that the AuNPs break into their smaller sizes right after addition of DA. The results confirm that the DMAP capped AuNPs are etched by the DA molecules due to the strong affinity between DA and AuNPs, thus causing a blue shift in the absorption spectrum. The concentration of DA is quantitatively monitored by using a UV-Vis spectrometer with a limit of detection (LOD) as low as 5 nM. In addition, the results also show that the methods developed appear to have no significant problems in detecting DA in the sample even with the presence of (10 mM) common interferents such as ascorbic acid (AA), homovanillic acid (HVA), catechol (CA) and glutathione (GSH). The developed AuNP etching protocol for dopamine detection provides a novel and versatile approach for rapid biosensing applications.

Topics: Ascorbic Acid; Catechols; Cyclic N-Oxides; Dopamine; Electrochemical Techniques; Glutathione; Gold; Homovanillic Acid; Metal Nanoparticles; Spectrophotometry, Ultraviolet; Toluene

Phenoloxidase from Artemia sinica (AsPO) was purified by Superdex 200 gel-filtration and Q Sepharose fast flow ion-exchange chromatography, and its properties were characterized biochemically and enzymatically by using L-dihydroxyphenylalanine (L-DOPA) as the specific substrate. Results showed that AsPO was isolated as a monomeric protein of 125.5 kDa in molecular mass. The optimal pH value and temperature are 7.0 and 50°C, respectively, for its PO activity. The AsPO had an apparent K(m) value of 4.2 mM on L-DOPA, and 10.9 mM on catechol, respectively. Oxidase inhibitor on PO activity showed that the AsPO was extremely sensitive to ascorbic acid, sodium sulfite, and citric acid; and was very sensitive to cysteine, benzoic acid, and 1-phenyl-2-thiourea. Combined with its specific enzyme activity on L-DOPA and catechol, it can be concluded that AsPO is most probably a typical catechol-type O-diphenoloxidase. Its PO activity was also sensitive to metal ions and chelators, and 20 mM DETC-inhibited PO activity was obviously recovered by 15 mM Cu(2+), indicating that AsPO is most probably a copper-containing metalloenzyme. All these data about specific substrate, sensitivity to oxidase inhibitor metal ions and chelators indicate that the AsPO has the properties of a catechol-type copper-containing O-diphenoloxidase that functions as a vital humoral factor in host defense via melaninization as in other Crustaceans.

Topics: Animals; Artemia; Ascorbic Acid; Benzoic Acid; Biocatalysis; Catechol Oxidase; Catechols; Citric Acid; Copper; Cysteine; Electrophoresis, Polyacrylamide Gel; Enzyme Assays; Enzyme Inhibitors; Hydrogen-Ion Concentration; Kinetics; Levodopa; Molecular Weight; Monophenol Monooxygenase; Phenylthiourea; Substrate Specificity; Sulfites; Temperature

This work describes the sensing properties of carbon paste electrodes (CPES) prepared from three different types of carbonaceous materials: graphite, carbon microspheres and carbon nanotubes. The electrochemical responses towards antioxidants including vanillic acid, catechol, gallic acid, L-ascorbic acid and L-glutathione have been analyzed and compared. It has been demonstrated that the electrodes based on carbon microspheres show the best performances in terms of kinetics and stability, whereas G-CPEs presented the smallest detection limit for all the antioxidants analyzed. An array of electrodes has been constructed using the three types of electrodes. As demonstrated by means of Principal Component Analysis, the system is able to discriminate among antioxidants as a function of their chemical structure and reactivity.

Topics: Antioxidants; Ascorbic Acid; Calibration; Carbon; Catechols; Electrochemical Techniques; Electrodes; Gallic Acid; Glutathione; Graphite; Kinetics; Limit of Detection; Microscopy, Electron, Scanning; Nanotubes, Carbon; Reproducibility of Results; Solutions; Vanillic Acid

The mechanisms of catechol-induced cytotoxicity were studied in cultures of neuroblastoma N2a cells. The minimal cytotoxic concentration after 72 h was 20 micromol x l(-1). The EC50 after 72 h was 38 micromol x l(-1). There was not a correlation between the cytotoxicity and the formation of quinones in the medium. Catechol-induced cytotoxicity was increased significantly when superoxide dismutase (SOD) was added. The addition of catalase did not protect cells, but this enzyme reverted the deleterious effect of SOD. The experimental studies showed a detrimental effect of deferoxamine on catechol-induced cytotoxicity suggesting that cells need iron to maintain its metabolism. NF-kappaB inhibitors increased the cytotoxicity, suggesting that this factor is also important for cell viability. L-cysteine and N-acetyl-L-cysteine protected cells significantly in a dose-dependent manner. The use of monochlorobimane showed that catechol induced reduced glutathione (GSH) depletion after 24 h, prior to cell death. The mode of cell death was studied by flow cytometry after double staining with annexin V and propidium iodide. Catechol induced apoptosis after 72 h. Furthermore, catechol also induced nuclear fragmentation. These data showed that catechol-induced cytotoxicity to N2a cell was not directly a consequence of reactive oxygen species production. Rather, it was due to GSH depletion followed by the induction of apoptosis.

Topics: Animals; Antioxidants; Apoptosis; Ascorbic Acid; Catechols; Cell Line, Tumor; Cell Survival; Curcumin; Cysteine; Cytotoxins; Deferoxamine; Glutathione; Mice; Neuroblastoma; NF-kappa B; Reactive Oxygen Species; Sesquiterpenes; Superoxide Dismutase

We have developed a chip-based nanofluidic device to amplify the electrochemical signal of catechols by orders of magnitude. The amplification is based on rapid redox cycling between plane parallel electrodes inside a nanochannel. We show that it is possible to monitor the signal of only a few hundred molecules residing in the active area of the nanofluidic sensor. Furthermore, due to the nanochannel design, the sensor is immune to interference by molecules undergoing irreversible redox reactions. We demonstrate the selectivity of the device by detecting catechol in the presence of ascorbic acid, whose oxidized form is only stable for a short time. The interference of ascorbic acid is usually a challenge in the detection of catecholamines in biological samples.

Topics: Ascorbic Acid; Biosensing Techniques; Catecholamines; Catechols; Electrochemistry; Electrodes; Microfluidic Analytical Techniques; Oxidation-Reduction; Sensitivity and Specificity; Silver; Silver Compounds

Microchip CE coupled with electrochemical detection (MCE-EC) is a good method for the direct detection of many small molecule analytes because the technique is sensitive and readily miniaturized. Polymer materials are being increasingly used with MCE due to their affordability and ease of fabrication. While PDMS has become arguably the most widely used material in MCE-EC due to the simplicity of microelectrode incorporation, it suffers from a lack of separation efficiency, lower surface stability, and a tendency for analyte sorption. Other polymers, such as poly(methylmethacrylate) (PMMA) and poly(carbonate) (PC), have higher separation efficiencies but require more difficult fabrication techniques for electrode incorporation. In this report, thermoset polyester (TPE) was characterized as an alternative material for MCE-EC. TPE microchips were characterized in their native and plasma oxidized forms and after coating with polyelectrolyte multilayers (PEMs). TPE provides higher separation efficiencies when compared to PDMS microchips, while still using simple fabrication protocols. In this work, separation efficiencies as high as 295,000 N/m were seen when using TPE MCE-EC devices. Furthermore, the EOF was higher and more consistent as a function of pH for both native and plasma-treated TPE than PDMS. Finally, TPE is amenable to modification using simple PEM coatings as another way to control surface chemistry and surface charge.

Topics: Ascorbic Acid; Carbohydrates; Catechols; Dopamine; Electrochemistry; Electrophoresis, Microchip; Microelectrodes; Polyesters; Polymers; Sulfhydryl Compounds; Surface Properties

Bacillus subtilis, a plant growth promoting rhizobacteria (PGPR), induces growth response and protection against pathogenic organisms through colonization and biofilm formation on the Arabidopsis thaliana root surface. In the current investigation, we utilized various Arabidopsis defense pathway mutants in a series of studies and showed that the plants recognize B. subtilis by a chemical-dependent cascade, which is independent of the salicylic acid (SA), jasmonic acid (JA), or ethylene pathways. These experiments revealed the importance of root surface chemistry in colonization and biofilm formation by B. subtilis. It was found that B. subtilis FB17 could not form biofilms on the roots of NahG, a transgenic Arabidopsis line for salicylate hydroxylase that produces catechol as the degradation product of SA. These findings suggest that catechol may play a direct role in inhibiting B. subtilis FB17 biofilm formation on the NahG root surface, possibly through induction of reactive oxygen species (ROS) in the roots. Using both in vitro microtitre plate and in planta assays we confirmed that catechol inhibited biofilm formation, but not the planktonic growth, of B. subtilis. Inhibition of biofilm formation was shown to be the result of a physiological response by B. subtilis to the presence of catechol, which resulted in the down-regulation of transcription of the yqxM-sipW-tasA and epsA-O operons, both of which are required for biofilm formation by B. subtilis. These data indicate that the suppression of biofilm formation on NahG plants was strongly influenced by the root-derived catechol production through ROS-mediated down-regulation of B. subtilis biofilm genes.

Topics: Arabidopsis; Ascorbic Acid; Bacillus subtilis; Biofilms; Catechols; Immunity, Innate; Mixed Function Oxygenases; Oxidative Stress; Plant Roots; Plants, Genetically Modified; Reactive Oxygen Species; Salicylic Acid

Equations are presented by which potential-volume data from redox titrations can be analyzed. Mixtures of analytes as well as of titrants may be analyzed, yielding for each component its concentration, number of electrons, and reduction potential. A novel weighting function ensures endpoint accuracy in fitting. Standard deviation of each parameter is obtained. The equations can be readily implemented in Microsoft Excel. Agreement with true values and good precision of fit parameters is demonstrated for a number of test cases. Use of these exact equations enables analysis of analyte mixtures without prior separation using single titrant or titrant mixtures. The equations were used to demonstrate that N-bromosuccinimide, a useful oxidant for organic analytes, undergoes hydrolysis.

Topics: Algorithms; Amines; Antioxidants; Ascorbic Acid; Bromosuccinimide; Catechols; Cerium; Electrochemistry; Ferricyanides; Hydrolysis; Least-Squares Analysis; Oxidation-Reduction; Titrimetry

The fabrication and characterization of boron-doped diamond microelectrodes for use in electrochemical detection coupled with capillary electrophoresis (CE-EC) is discussed. The microelectrodes were prepared by coating thin films of polycrystalline diamond on electrochemically sharpened platinum wires (76-, 25-, and 10-microm diameter), using microwave-assisted chemical vapor deposition (CVD). The diamond-coated wires were attached to copper wires (current collectors), and several methods were explored to insulate the cylindrical portion of the electrode: nail polish, epoxy, polyimide, and polypropylene coatings. The microelectrodes were characterized by scanning electron microscopy, Raman spectroscopy, and cyclic voltammetry. They exhibited low and stable background currents and sigmoidally shaped voltammetric curves for Ru(NH3)6(3+/2+) and Fe(CN)6(3-/4-) at low scan rates. The microelectrodes formed with the large diameter Pt and sealed in polypropylene pipet tips were employed for end-column detection in CE. Evaluation of the CE-EC system and the electrode performance were accomplished using a 10 mM phosphate buffer, pH 6.0, run buffer, and a 30-cm-long fused-silica capillary (75-microm i.d.) with dopamine, catechol, and ascorbic acid serving as test analytes. The background current (approximately 100 pA) and noise (approximately 3 pA) were measured at different detection potentials and found to be very stable with time. Reproducible separation (elution time) and detection (peak current or area) of dopamine, catechol, and ascorbic acid were observed with response precisions of 4.1% or less. Calibration curves constructed from the peak area were linear over 4 orders of magnitude, up to a concentration between 0.1 and 1 mM. Mass limits of detection for dopamine and catechol were 1.7 and 2.6 fmol, respectively (S/N = 3). The separation efficiency was approximately 33,000, 56,000, and 98,000 plates/m for dopamine, catechol, and ascorbic acid, respectively. In addition, the separation and detection of 1- and 2-naphthol in 160 mM borate buffer, pH 9.2, was investigated. Separation of these two analytes was achieved with efficiencies of 118,000 and 126,000 plates/m, respectively.

Topics: Ascorbic Acid; Boron; Catechols; Diamond; Dopamine; Electrochemistry; Electrophoresis, Capillary; Microelectrodes

5-methyl-2'-deoxycytidine (5-Me-dC) is formed by the enzymatic methylation of dC, primarily in CpG sequences in DNA, and is involved in the regulation of gene expression. In the present study, 5-Me-dC and double-stranded DNA fragments containing 5-Me-dC were either gamma-irradiated or aerobically treated with Fenton-type reagents, Fe(II)-EDTA, Fe(II)-nitrilotriacetic acid, Fe(III)-EDTA-H(2)O(2)-catechol or ascorbic acid-H(2)O(2) under neutral conditions. The formation of 5-formyl-2'-deoxycytidine (5-CHO-dC) was observed upon treatment of both 5-Me-dC and DNA fragments containing 5-Me-dC. The yields of 5-CHO-dC from 5-Me-dC and those of 5-formyl-2'-deoxyuridine from dT were comparable. These results suggest that 5-Me-dC in DNA is as susceptible to oxidation as dT in cells, and raise the possibility that 5-CHO-dC may contribute to the high mutagenic rate observed in CpG sequences in genomic DNA.

Topics: Ascorbic Acid; Catechols; CpG Islands; Deoxycytidine; Deoxyribonucleosides; DNA; Edetic Acid; Ferric Compounds; Ferrous Compounds; Gamma Rays; Hydrogen Peroxide; Iron; Oxidation-Reduction

Topics: Ascorbic Acid; Basidiomycota; Calorimetry; Catechols; Enzymes, Immobilized; Food Analysis; Hydroquinones; Laccase; Oxidoreductases; Substrate Specificity; Thermodynamics

Differential pulse voltammetry with treated carbon fibre micro-electrodes has been successfully employed in in vivo analysis of neurotransmitter release and metabolism. This methodology has been now applied to ex vivo preparations (brain slices) in order to study diverse neurotransmitter activities in various brain regions ipsilateral and controlateral to a middle cerebral artery (MCA) occlusion performed in anaesthetised adult male rats. Data demonstrated that significant changes of voltammetric ascorbic acid levels related to the ischaemic state were monitored within the ipsilateral to MCA occlusion frontal cortex, striatum, nucleus accumbens and hippocampus which were the brain area studied. Furthermore, it appeared that voltammetric catecholaminergic and 5-hydroxy indolaminergic values measured within the nucleus accumbens controlateral to MCA occlusion differ significantly from the results monitored with the same technique in brain slices obtained from sham rats. In various studies, the brain regions contralateral to MCA occlusion are generally considered as control areas, however, the present data suggest that the nucleus accumbens contralateral to the MCA occlusion side is specifically affected by the ischaemic state.

Topics: Animals; Ascorbic Acid; Brain; Brain Ischemia; Catechols; Cerebral Arteries; Cerebral Cortex; Corpus Striatum; Electrochemistry; Functional Laterality; Hippocampus; In Vitro Techniques; Indoles; Male; Microelectrodes; Neuropeptides; Neurotransmitter Agents; Organ Specificity; Rats; Rats, Sprague-Dawley

The healing-promotion property of saliva has been observed in the past, but its underlying mechanism has never been elucidated. We hypothesized a mechanism based on salivary proteins binding to redox active metal ions, rendering them nonactive in their capacity for free radical production.. Examination of this mechanism was conducted by comparing the redox activity of protein-rich saliva with protein-poor saliva. We also examined the redox activity mediated by these 2 kinds of saliva following the in vitro addition of iron, copper, and manganese. Saliva samples were analyzed for their redox activity by measuring the ascorbate-driven and saliva (diluted 1:2)-mediated conversion of salicylate to its 2,3- and 2.5-dihydroxybenzoates and catechol metabolites.. The concentrations of salicylate metabolites formed by protein-rich saliva were significantly lower by 45% (P < .05), 66% (P < .01), and 54% (P < .05), respectively, when compared with those formed by protein-poor saliva. The capacity of saliva in suppressing redox activity was found to be inversely related to the concentrations of iron and copper added (but not manganese), but correlated well with the protein content. When the highest concentrations of iron (15 mumol/L) and copper (10 mumol/L) were added to protein-rich saliva, the concentrations of salicylate metabolites produced were only 0.3% to 1% of those of non-saliva-containing controls (P < .01). However, when these concentrations of iron and copper were added to protein-poor saliva, significantly higher values of redox activity were detected, and the concentrations of the salicylate derivatives produced were 2.1% to 8.1% of those of non-saliva-containing controls (P < .01). In contrast, when the lowest concentrations of iron (2 mumol/L) and copper (0.1 mumol/L) were added, 2.8 to 4 times lower concentrations of salicylate derivatives were produced (P < .01).. These results substantiate our hypothesis that saliva has a profound capacity for reducing redox activity rendered by transition metal ions, correlating well with its protein content.

Topics: Ancitabine; Animals; Antimetabolites, Antineoplastic; Antioxidants; Ascorbic Acid; Catechols; Copper; Free Radicals; Gentisates; Hydroxybenzoates; Iron; Iron Chelating Agents; Male; Manganese; Metals; Oxidation-Reduction; Parasympathomimetics; Parotid Gland; Pilocarpine; Protein Binding; Rats; Rats, Wistar; Salicylates; Saliva; Salivary Proteins and Peptides; Wound Healing

Differential pulse voltammetry and more recently cyclic voltammetry have been successfully used to monitor basal levels of endogenous chemicals by means of treated carbon fibre microbiosensors inserted in specific brain regions. In this study, feasibility of concomitant in vivo recordings of stable electrophysiological signals and basal ascorbate, catecholaminergic and indolaminergic voltammetric peaks at the same cerebral site by means of a single electrically treated carbon fibre micro electrode (microbiosensor) is presented. The results indicate that these two independent techniques can be combined in vivo at a single electrode, and that voltammetric measurements of unstimulated levels of extracellular compounds do not alter concomitant basal cell firing for a period long enough (more than 6 h) to allow pharmacological manipulations.

Topics: 3,4-Dihydroxyphenylacetic Acid; Animals; Ascorbic Acid; Biosensing Techniques; Brain; Carbon; Carbon Fiber; Catechols; Electric Stimulation; Electrodes, Implanted; Electrophysiology; Feasibility Studies; Hydroxyindoleacetic Acid; Indoles; Microelectrodes; Nucleus Accumbens; Rats

Catechol 2,3-dioxygenase encoded by TOL plasmid pWW0 of Pseudomonas putida consists of four identical subunits, each containing one ferrous ion. The enzyme catalyzes ring cleavage of catechol, 3-methylcatechol, and 4-methylcatechol but shows only weak activity toward 4-ethylcatechol. Two mutants of catechol 2,3-dioxygenases (4ECR1 and 4ECR6) able to oxidize 4-ethylcatechol, one mutant (3MCS) which exhibits only weak activity toward 3-methylcatechol but retained the ability to cleave catechol and 4-methylcatechol, and one phenotypic revertant of 3MCS (3MCR) which had regained the ability to oxidize 3-methylcatechol were characterized by determining their Km and partition ratio (the ratio of productive catalysis to suicide catalysis). The amino acid substitutions in the four mutant enzymes were also identified by sequencing their structural genes. Wild-type catechol 2,3-dioxygenase was inactivated during the catalysis of 4-ethylcatechol and thus had a low partition ratio for this substrate, whereas the two mutant enzymes, 4ECR1 and 4ECR6, had higher partition ratios for it. Similarly, mutant enzyme 3MCS had a lower partition ratio for 3-methylcatechol than that of 3MCR. Molecular oxygen was required for the inactivation of the wild-type enzyme by 4-ethylcatechol and of 3MCS by 3-methylcatechol, and the inactivated enzymes could be reactivated by incubation with FeSO4 plus ascorbic acid. The enzyme inactivation is thus most likely mechanism based and occurred principally by oxidation and/or removal of the ferrous ion in the catalytic center. In general, partition ratios for catechols lower than 18,000 did not support bacterial growth. A possible meaning of the critical value of the partition ratio is discussed.

Topics: Ascorbic Acid; Catechol 2,3-Dioxygenase; Catechols; Cell Division; Dioxygenases; Enzyme Reactivators; Ferrous Compounds; Iron; Kinetics; Mutation; Oxygen; Oxygenases; Plasmids; Pseudomonas putida; Substrate Specificity

There is evidence to suggest that degeneration of dopaminergic neurons in Parkinson's disease and certain other conditions results from the action of reactive species generated during the oxidation of dopamine. We, therefore, have begun to explore the conditions under which such reactive species are formed. Tissue slices prepared from rat neostriatum were incubated in a standard Krebs bicarbonate buffer for up to 120 min. In the presence of [3H]dopamine (0.01-100 microM), binding of tritium to the acid-insoluble protein fraction was detected. Binding was attenuated by the addition of ascorbate (0.085-0.85 mM) or glutathione (0.01-1.0 mM) to the buffer. Acid hydrolysis of the protein revealed the presence of cysteinyl-dopamine and cysteinyl-dihydroxyphenylacetic acid residues. These results suggest that dopamine oxidizes to form reactive metabolites, presumably quinones, that then bind to nucleophilic sulfhydryl groups on protein cysteinyl residues. The findings further suggest that the extent to which reactive metabolites are formed is determined in part by the balance between the availability of dopamine and the antioxidant environment.

Topics: 3,4-Dihydroxyphenylacetic Acid; Animals; Ascorbic Acid; Catechols; Chromatography, High Pressure Liquid; Cysteine; Dopamine; Glutathione; Male; Neostriatum; Nerve Tissue Proteins; Rats; Rats, Sprague-Dawley; Tritium

Electrodes modified by the electrodeposition of poly(3-methylthiophene) were used as chemical sensors for some organic and biological molecules of industrial and medicinal interest. The electrochemical behaviors of ferri/ferrocyanide, catechol, ascorbic acid, hydroquinone, dopamine epinephrine, acetaminophen, p-aminophenol and NADH were examined by cyclic voltammetry. The results showed that the proposed modified surface catalyzes the oxidation of these compounds. Differential pulse and square wave techniques were used for the analysis of binary mixture of ascorbic acid with catechol, NADH, dopamine and p-aminophenol. Voltammetric peak resolution was also demonstrated for a ternary mixture of ascorbic acid, catechol and p-aminophenol. Polymer coated electrode was also used in an amperometric detector for flow injection analysis of most of the aforementioned compounds. The responses of the polymer electrode were 4-10 times larger as compared to those of platinum. The modified electrode displayed excellent response stability for successive injections and detection limits were 10 ppb for catechol, dopamine, epinephrine, NADH and p-aminophenol, 1 ppb for acetaminophen and 100 ppb for ascorbic acid. Voltammetric peak positions were affected by the nature of the electrolyte and its pH. Also, film thicknesses were shown to be a factor affecting both the current magnitudes and oxidation peak potential of NADH.

Topics: Acetaminophen; Aminophenols; Ascorbic Acid; Biosensing Techniques; Catechols; Dopamine; Electrochemistry; Epinephrine; Hydroquinones; Iron; NAD; Polymers; Thiophenes

Potential second-stage modifying effects of 8 antioxidants on lung tumorigenesis initiated by N-bis(2-hydroxypropyl)nitrosamine (DHPN) were examined in male F344 rats. After an initial 2-week treatment with DHPN (0.1% in drinking water), rats were administered one of the antioxidants supplemented in the diet for 30 weeks. Although the incidences of lung adenomas were not affected, those of carcinomas were lowered by 2% butylated hydroxyanisole (BHA, 2 rats/20 rats), 1% butylated hydroxytoluene (BHT, 1/20), 0.8% ethoxyquin (EQ, 3/20) and 1% a-tocopherol (a-TP, 2/20) treatments as compared to the control level (9/20), while 5% sodium L-ascorbate (SA), 0.8% catechol (CC), 0.8% resorcinol (RN), and 0.8% hydroquinone (HQ) did not exert any significant effect on incidence. Quantitative analysis of adenomas and carcinomas (numbers and areas of lesions per unit area of lung section) revealed obvious inhibitory effects of SA, CC, and RN as well as BHA, BHT, EQ, and a-TP. Among the antioxidants, BHT exerted the strongest inhibitory activity. In contrast, DHPN-induced thyroid tumorigenesis was significantly enhanced by BHT (14/20) and EQ (20/20) treatments (control = 5/20). Thus the antioxidants showed opposite effects on lung and thyroid carcinogenesis in the rat.

Topics: Adenoma; Animals; Antioxidants; Ascorbic Acid; Body Weight; Butylated Hydroxyanisole; Butylated Hydroxytoluene; Carcinoma; Catechols; Ethoxyquin; Hydroquinones; Kidney Neoplasms; Lung Neoplasms; Male; Nitrosamines; Organ Size; Rats; Rats, Inbred F344; Resorcinols; Thyroid Neoplasms; Urinary Bladder Neoplasms; Vitamin E

Inhibition potential of concomitant butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), catechol or sodium ascorbate (Na-AsA) administration on development of diethylnitrosamine (DEN) initiated glutathione S-transferase placental form (GST-P) positive foci in rat liver under the influence of 2-acetylaminofluorene (2-AAF) or 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB) plus partial hepatectomy (PH) was investigated. Whereas BHA, BHT and catechol exerted marked inhibitory effects, Na-AsA lacked any modifying potential. The compounds that demonstrated inhibition also induced GST-P in the hepatic periportal areas, suggesting that development of GST-P positive foci is negatively influenced by extra-focal increase in this enzyme form observed with BHA, BHT or catechol.

Topics: 2-Acetylaminofluorene; Animals; Ascorbic Acid; Butylated Hydroxyanisole; Catechols; Diethylnitrosamine; Enzyme Induction; Glutathione Transferase; Liver; Male; Methyldimethylaminoazobenzene; Rats; Rats, Inbred F344

We have studied the binding of the dopaminergic agonist 2-[5,8-3H]amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene [( 3H]ADTN) to hypothalamic membranes from the genetically diabetic-obese (db/db) mice and their lean littermates. The specific binding of [3H]ADTN was defined as the difference between the radioligand binding to the membranes in the absence or presence of 1 microM (+)-butaclamol. In order to control nonspecific binding, all binding assays were performed in the presence of 0.1 mM catechol and 0.3 mM ascorbic acid. Binding of [3H]ADTN was rapid, dissociable, saturable and stereoselective. (+)-Butaclamol was very potent whereas (-)-butaclamol was ineffective in inhibiting the binding of this radioligand. Concentration-dependent binding experiments and Scatchard analysis of the data yielded dissociation constant (Kd) of 3.5-4.2 nM and number of binding sites (n) equivalent to 170-200 fmol/mg protein for lean mice. For db/db mice, the data yielded a Kd of 4.0-4.7 nM and an n of 400-500 fmol/mg protein. It was also shown that the anorexic drugs, amphetamine and fenfluramine, inhibited [3H]ADTN binding in a dose-dependent manner. Binding parameters, obtained using membranes from mice made obese by parenteral administration of gold thioglucose, were not significantly different from those obtained for the lean mice. It is concluded that the regulation of the hypothalamic dopaminergic receptors may be related to the lesion in the genetically obese mice.

Topics: Adenylyl Cyclases; Amphetamines; Animals; Ascorbic Acid; Aurothioglucose; Catechols; Diabetes Mellitus, Experimental; Fenfluramine; Hypothalamus; Kinetics; Mice; Mice, Mutant Strains; Mice, Obese; Obesity; Radioligand Assay; Receptors, Dopamine; Stereoisomerism; Tetrahydronaphthalenes

Topics: Ascorbic Acid; Catechols; Chloroplasts; Electron Transport; Hot Temperature; Oxidation-Reduction; Plants

It has been pointed out by several different groups of investigators in the past several years that ascorbic acid was a potent inhibitor of the binding of dopamine (DA) agonists including 3H-DA itself and 3H-ADTN, 3H-apomorphine and 3H-norpropylapomorphine to neostriatal membrane preparations. However, the significance of this effect of ascorbic acid has been controversial. For example, it has recently been claimed that the stereospecific binding of DA agonists is facilitated by ascorbic acid and can be measured only in its presence. In the present study in neostriatal membrane preparations in the absence of ascorbic acid, the binding of 3H-DA was very potently inhibited by potent DA agonists (DA, ADTN, apomorphine). Considerably weaker effects were obtained with norepinephrine, isoproterenol, serotonin, catechol and pyrogallol. Stereospecific effects were clearly observed in that the binding of 3H-DA was inhibited to a much greater extent by several biologically active enantiomers than by their less active counterparts. For example, (-)-2-hydroxyapomorphine and (-)-norpropylapomorphine were much more potent inhibitors than their corresponding (+) isomers. This binding of 3H-DA was also very strongly inhibited by sodium ascorbate and several other reducing agents. In control experiments in the neostriatal membrane preparation in the absence of ascorbic acid, there was no detectable decomposition of 3H-DA. The data suggest that 3H-DA can, in the absence of sodium ascorbate, bind stereospecifically to a site that has the properties of a DA receptor. Furthermore, sodium ascorbate is a potent inhibitor of this stereospecific binding.

Topics: Animals; Ascorbic Acid; Catechols; Corpus Striatum; Dopamine; Dose-Response Relationship, Drug; Male; Membranes; Pyrogallol; Rats; Rats, Inbred Strains; Stereoisomerism

Topics: Ascorbic Acid; Catechols; Dihydroxyphenylalanine; Glass Ionomer Cements; Melanins; Metabolism; Pharmacology; Pigmentation; Research; Thiourea; Tyrosine; Tyrosine Decarboxylase; Verticillium

Topics: Animals; Ascorbic Acid; Bombyx; Catechols; Chlorogenic Acid; Colorimetry; Copper; Cresols; Cysteine; Dihydroxyphenylalanine; Electron Spin Resonance Spectroscopy; Ferrocyanides; Hydroquinones; Manometry; Monophenol Monooxygenase; Oxidoreductases; Phenols; Research; Spectrum Analysis

Topics: Adrenochrome; Ascorbic Acid; Catechols; Cats; Chlorpromazine; Cyanides; Cytochromes; Dihydroxyphenylalanine; Epinephrine; Glutathione; Hydrazines; Metabolism; Monoamine Oxidase; Monoamine Oxidase Inhibitors; Oxidation-Reduction; Parotid Gland; Pharmacology; Phenylhydrazines; Research; Salivary Glands; Sulfhydryl Compounds; Sympathomimetics; Tritium; Tyrosine

Topics: Animals; Ascorbic Acid; Catechols; Chemical Phenomena; Chemistry; Coleoptera; Cresols; Dihydroxyphenylalanine; Enzyme Inhibitors; Kinetics; Larva; Monophenol Monooxygenase; Oxidoreductases; Phenols; Phenylacetates; Propionates; Research; Tenebrio; Tyramine; Tyrosine

Topics: Ascorbic Acid; Capillary Resistance; Catechin; Catechols; Guinea Pigs; Metabolism; Pharmacology; Research; Rutin

Topics: 17-Ketosteroids; Adrenalectomy; Ascorbic Acid; Catechols; Edema; Formaldehyde; Hyaluronoglucosaminidase; Inflammation; Pharmacology; Rats; Research; Tannins; Tea; Urine

Topics: Ascorbic Acid; Catalase; Catechols; Metabolism; Pharmacology; Phenols; Pyrogallol; Resorcinols; Staphylococcus; Sulfadiazine; Sulfaguanidine; Sulfanilamide; Sulfanilamides; Sulfisoxazole; Sulfonamides; Thymol

Topics: Animals; Ascorbic Acid; Catechols; Fetus; Pantothenic Acid; Rats; Vitamin B Deficiency; Vitamins

Topics: Animals; Ascorbic Acid; Catechols; Pantothenic Acid; Pregnancy; Rats; Vitamin B Deficiency; Vitamins

Topics: Adrenal Glands; Ascorbic Acid; Catechols; Sodium

Topics: Ascorbic Acid; Catechols; Humans; Vitamins

Topics: Ascorbic Acid; Catechol Oxidase; Catechols; Copper; Monophenol Monooxygenase; Oxidoreductases; Vitamins

1. A number of tissues, in particular, brain, liver, and kidney, incubated aerobically in vitro as slices or ground suspensions produce a compound which combines with p-aminobenzoic acid in acid solution to form a yellow color. 2. A study of this reaction in rat brain has shown that this compound can be produced when washed boiled brain protein is incubated aerobically with ascorbic acid. The latter acts as a catalyst to break the linkage between the protein and the compound. Oxygen is taken up in the process. 3. A number of aromatic hydroxy compounds such as epinephrine and catechol inhibit the reaction. Cyanide has little or no effect. No reaction occurs anaerobically. 4. The occurrence of the reaction in some animals has been described.

Topics: Animals; Ascorbic Acid; Catalysis; Catechols; Kidney; Oxidation-Reduction; Proteins; Rats