Sample records for 1,2-dihydroxybenzene

  1. Biocatalyzed cross-coupling of sinomenine and 1,2-dihydroxybenzene by Coriolus unicolor

    Zhang Shuang Deng; Dan Zhao; Yi Hu; Jian Xin Li; Kun Zou; Jun Zhi Wang


    Sinomenine is a clinically available drug for the treatment of rheumatoid arthritis (RA).In a continuous research aiming at discovery of sinomenine derivates with better bioactivity,a cross-coupling reaction of sinomenine and 1,2-dihydroxybenzene catalyzed by a fungus Coriolus unicolor afforded an unique C-C cross-coupled compound 2,together with (S)-disinomenine and (R)-disinomenine.The structure of 2 was elucidated by MS and NMR spectroscopy.Compound 2 was further assayed for the inhibitory activity on IL-6 overproduction in SW982 cells and exhibited a much more potent activity on IL-6 (96% inhibition)compared with those of (S)-disinomenine and sinomenine (17% and 12% inhibition,respectively).

  2. FTIR study of H-bonds cooperativity in complexes of 1,2-dihydroxybenzene with proton acceptors in aprotic solvents: influence of the intramolecular hydrogen bond.

    Varfolomeev, Mikhail A; Abaidullina, Dilyara I; Gainutdinova, Aliya Z; Solomonov, Boris N


    FTIR spectroscopic study of hydrogen bonding of 1,2-dihydroxybenzene (catechol) with proton acceptors has been carried out. The influence of intramolecular and intermolecular hydrogen bonds on the strengths of each other in complexes of 1,2-dihydroxybenzene with various proton acceptors has been analyzed. It was shown that intramolecular hydrogen bond is strengthened when 1,2-dihydroxybenzene interacts with bases (ethers, amines, nitriles, etc.) in inert solvents. The contribution of the cooperativity of intramolecular hydrogen bonds in the frequency of stretching vibrations of O-H groups linearly depends on the proton acceptor ability of the bases. The solvent effect on hydrogen bond cooperativity in 1,2-dihydroxybenzene-base complexes has been studied. The approach to determine the influence of cooperative effects on the formation of intermolecular complexes with 1,2-dihydroxybenzene is proposed. It was shown that the strength of intramolecular hydrogen bonds in the complexes of 1,2-dihydroxybenzene with bases due to cooperativity of interactions increases by 30-70%, and the strength of intermolecular hydrogen bond by 7-22%.

  3. The role of the interaction between oxygen and catechol in the pitting corrosion of steel in alkaline sulfide solutions

    Kannan, S.; Kelly, R.G. [Univ. of Virginia, Charlottesville, VA (United States)


    Black liquor corrosivity is shown to depend on the interaction of the chemical species present. Specifically, an interaction between oxygen and 1,2-dihydroxybenzene compounds (catechols) in alkaline sulfide solutions leads to a distinct increase in the severity of the attack. This increased corrosivity is explained in terms of the oxidation of catechol leading to increased open circuit potentials for steel. The importance of the ratio of sulfide concentration to hydroxyl concentration in the initiation of pitting is stressed. The possible role of catechol in stabilizing metastable pits is also discussed.

  4. Effects of structural isomerism on solution behaviour of solutes: Apparent molar volumes and isentropic compression of catechol, resorcinal, and hydroquinone in aqueous solution at T = (283.15, 293.15, 298.15, 303.15, and 313.15) K

    Bayram, Edip [Department of Chemistry, Akdeniz University, Antalya 07058 (Turkey); Ayranci, Erol, E-mail: [Department of Chemistry, Akdeniz University, Antalya 07058 (Turkey)


    Effects of structural isomerism on solution behaviour of dihydroxybenzenes were examined through the determination of volumetric properties such as apparent molar volumes, apparent molar isentropic compressions, and isobaric expansions. The isomers were 1,2-dihydroxybenzene (catechol), 1,3-dihydroxybenzene (resorcinol), and 1,4-dihydroxybenzene (hydroquinone). The volumetric properties were determined from accurate density and speed of sound measurements at T = (283.15, 293.15, 298.15, 303.15, and 313.15) K and at various concentrations. Values at infinite dilution of these parameters were obtained by suitable extrapolation procedures. The results are discussed in terms of hydrophobic, hydrogen bonding, and dipole-dipole interactions between the three isomers and water. Catechol was found to have the strongest hydrophilic and the weakest hydrophobic interactions with water among the three isomers.

  5. Exploring redox-mediating characteristics of textile dye-bearing microbial fuel cells: thionin and malachite green.

    Chen, Bor-Yann; Xu, Bin; Qin, Lian-Jie; Lan, John Chi-Wei; Hsueh, Chung-Chuan


    Prior studies indicated that biodecolorized intermediates of azo dyes could act as electron shuttles to stimulate wastewater decolorization and bioelectricity generation (WD&BG) in microbial fuel cells (MFCs). This study tended to explore whether non-azo textile dyes (i.e., thionin and malachite green) could also own such redox-mediating capabilities for WD&BG. Prior findings mentioned that OH and/or NH2 substitute-containing auxochrome compounds (e.g., 2-aminophenol and 1,2-dihydroxybenzene) could effectively mediate electron transport in MFCs for simultaneous WD&BG. This work clearly suggested that the presence of electron-mediating textile dyes (e.g., thionin and malachite green (MG)) in MFCs is promising to stimulate color removal and bioelectricity generation. That is, using MFCs as operation strategy for wastewater biodecolorization is economically promising in industrial applications due to autocatalytic acceleration of electron-flux for WD&BG in MFCs.

  6. Atmospheric oxidation of selected hydrocarbons

    Benter, T.; Olariu, R.I.


    This work presents investigations on the gas-phase chemistry of phenol and the cresol isomers performed in a 1080 l quartz glass reactor in Wuppertal and in a large-volume outdoor photoreactor EUPHORE in Valencia, Spain. The studies aimed at clarifying the oxidation mechanisms of the reactions of these compounds with OH and NO{sub 3} radicals. Product investigations on the oxidation of phenol and the cresol isomers initiated by OH radicals were performed in the 1080 l quartz glass reactor with analyses by in situ FT-IR absorption spectroscopy. The primary focus of the investigations was on the determination of product yields. This work represents the first determination and quantification of 1,2-dihydroxybenzenes in the OH oxidation of phenolic compounds. Possible reaction pathways leading to the observed products have been elucidated. (orig.)

  7. Thermal transformation of bioactive caffeic acid on fumed silica seen by UV-Vis spectroscopy, thermogravimetric analysis, temperature programmed desorption mass spectrometry and quantum chemical methods.

    Kulik, Tetiana V; Lipkovska, Natalia O; Barvinchenko, Valentyna M; Palyanytsya, Borys B; Kazakova, Olga A; Dudik, Olesia O; Menyhárd, Alfréd; László, Krisztina


    Thermochemical studies of hydroxycinnamic acid derivatives and their surface complexes are important for the pharmaceutical industry, medicine and for the development of technologies of heterogeneous biomass pyrolysis. In this study, structural and thermal transformations of caffeic acid complexes on silica surfaces were studied by UV-Vis spectroscopy, thermogravimetric analysis, temperature programmed desorption mass spectrometry (TPD MS) and quantum chemical methods. Two types of caffeic acid surface complexes are found to form through phenolic or carboxyl groups. The kinetic parameters of the chemical reactions of caffeic acid on silica surface are calculated. The mechanisms of thermal transformations of the caffeic chemisorbed surface complexes are proposed. Thermal decomposition of caffeic acid complex chemisorbed through grafted ester group proceeds via three parallel reactions, producing ketene, vinyl and acetylene derivatives of 1,2-dihydroxybenzene. Immobilization of phenolic acids on the silica surface improves greatly their thermal stability.

  8. Intensification of volatile organic compounds mass transfer in a compact scrubber using the O3/H2O2 advanced oxidation process: kinetic study and hydroxyl radical tracking.

    Biard, Pierre-François; Couvert, Annabelle; Renner, Christophe; Levasseur, Jean-Pierre


    This study assesses the potential of ozonation and advanced oxidation process O(3)/H(2)O(2) to enhance the dimethyldisulfide (DMDS) mass transfer in a compact chemical scrubber developed for air treatment applications. Theoretical calculations, through Hatta number and enhancement factor evaluations for two parallel irreversible reactions, were compared to experimental data and enabled the description of the mass transfer mechanisms. These calculations required the determination of the kinetic constant of the DMDS oxidation by molecular ozone ( [Formula: see text] ) and the measurement of the hydroxyl radical concentration within the scrubber. The competitive kinetic method using the 1,2-dihydroxybenzene (resorcinol) enabled to determine a value of the kinetic constant [Formula: see text] of 1.1×10(6)M(-1)s(-1) at 293K. Then, experiments using para-chlorobenzoic acid in solution allowed measuring the average hydroxyl concentration in the scrubber between the inlet and the outlet depending on the chemical conditions (pH and inlet O(3) and H(2)O(2) concentrations). High hydroxyl radical concentrations (10(-8)M) and ratio of the HO°-to-O(3) exposure (R(ct)≈10(-4)) were put in evidence.

  9. Secondary Organic Aerosol formation from the gas-phase reaction of catechol with ozone

    Coeur-Tourneur, C.; Tomas, A.; Guilloteau, A.; Henry, F.; Ledoux, F.; Visez, N.; Riffault, V.; Wenger, J. C.; Bedjanian, Y.; Foulon, V.


    The formation of secondary organic aerosol from the gas-phase reaction of catechol (1,2-dihydroxybenzene) with ozone has been studied in two smog chambers (at the LPCA in France and at the CRAC in Ireland). Aerosol production was monitored using a scanning mobility particle sizer. The overall organic aerosol yield (Y) was determined as the ratio of the suspended aerosol mass corrected for wall losses (Mo) to the total reacted catechol concentrations, assuming a particle density of 1.4 g cm-3. Analysis of the data clearly shows that Y is a strong function of Mo and that secondary organic aerosol formation can be expressed by a one-product gas/particle partitioning absorption model. The aerosol formation is affected by the initial catechol concentration, which leads to aerosol yields ranging from 17% to 86%. The aerosol yields determined in the LPCA and CRAC smog chambers were comparable and were also in accordance with those determined in a previous study performed in EUPHORE (EUropean PHOto REactor, Spain).

  10. Aerosol formation yields from the reaction of catechol with ozone

    Coeur-Tourneur, Cécile; Tomas, Alexandre; Guilloteau, Angélique; Henry, Françoise; Ledoux, Frédéric; Visez, Nicolas; Riffault, Véronique; Wenger, John C.; Bedjanian, Yuri

    The formation of secondary organic aerosol from the gas-phase reaction of catechol (1,2-dihydroxybenzene) with ozone has been studied in two smog chambers. Aerosol production was monitored using a scanning mobility particle sizer and loss of the precursor was determined by gas chromatography and infrared spectroscopy, whilst ozone concentrations were measured using a UV photometric analyzer. The overall organic aerosol yield ( Y) was determined as the ratio of the suspended aerosol mass corrected for wall losses ( Mo) to the total reacted catechol concentrations, assuming a particle density of 1.4 g cm -3. Analysis of the data clearly shows that Y is a strong function of Mo and that secondary organic aerosol formation can be expressed by a one-product gas-particle partitioning absorption model. The aerosol formation is affected by the initial catechol concentration, which leads to aerosol yields ranging from 17% to 86%. The results of this work are compared to similar studies reported in the literature.

  11. Biocatalytic carboxylation of phenol derivatives: kinetics and thermodynamics of the biological Kolbe-Schmitt synthesis.

    Pesci, Lorenzo; Glueck, Silvia M; Gurikov, Pavel; Smirnova, Irina; Faber, Kurt; Liese, Andreas


    Microbial decarboxylases, which catalyse the reversible regioselective ortho-carboxylation of phenolic derivatives in anaerobic detoxification pathways, have been studied for their reverse carboxylation activities on electron-rich aromatic substrates. Ortho-hydroxybenzoic acids are important building blocks in the chemical and pharmaceutical industries and are currently produced via the Kolbe-Schmitt process, which requires elevated pressures and temperatures (≥ 5 bar, ≥ 100 °C) and often shows incomplete regioselectivities. In order to resolve bottlenecks in view of preparative-scale applications, we studied the kinetic parameters for 2,6-dihydroxybenzoic acid decarboxylase from Rhizobium sp. in the carboxylation- and decarboxylation-direction using 1,2-dihydroxybenzene (catechol) as starting material. The catalytic properties (K(m), V(max)) are correlated with the overall thermodynamic equilibrium via the Haldane equation, according to a reversible random bi-uni mechanism. The model was subsequently verified by comparing experimental results with simulations. This study provides insights into the catalytic behaviour of a nonoxidative aromatic decarboxylase and reveals key limitations (e.g. substrate oxidation, CO2 pressure, enzyme deactivation, low turnover frequency) in view of the employment of this system as a 'green' alternative to the Kolbe-Schmitt processes.

  12. Antioxidant enzymes are induced by phenol in the marine microalga Lingulodinium polyedrum.

    Martins, P L G; Marques, L G; Colepicolo, P


    Knowing the impacts of different anthropogenic activities on ecosystems promotes preservation of aquatic organisms. Aiming to facilitate the identification of polluted or contaminated areas, the study of microalga Lingulodinium polyedrum in phenol-containing medium comprises the determination of toxic and metabolic phenol effects, featuring a possible use of this microorganism as bioindicator for this pollutant. Marine microalga L. polyedrum exposure to phenol increases superoxide dismutase (SOD) and catalase (CAT) activities. The 20% and 50% inhibitory concentrations (IC20 and IC50) of cells exposed to phenol were 40 μmol L(-1) and 120 μmol L(-1), respectively. Phenol biodegradation by L. polyedrum was 0.02 μmol h(-1)cell(-1), and its biotransformation was catalyzed by glutathione S-transferase (GST), phenol hydroxylase and catechol 2,3-dihydroxygenase metabolic pathways. Phenol exposure produced the metabolites 2-hydroxymuconic semialdehyde acid, 1,2-dihydroxybenzene (catechol), and 2-oxo-4-pentenoic acid; also, it induced the activity of key antioxidant biomarker enzymes SOD and CAT by three folds compared to that in the controls. Further, phenol decreased the glutathione/oxidized glutathione ratio (GSH/GSSG), highlighting the effective glutathione oxidation in L. polyedrum. Overall, our results suggest that phenol alters microalga growth conditions and microalgae are sensitive bioindicators to pollution by phenol in marine environments.

  13. Theoretical Study on Reaction Pathways Leading to CO and CO2 in the Pyrolysis of Resorcinol.

    Furutani, Yuki; Kudo, Shinji; Hayashi, Jun-Ichiro; Norinaga, Koyo


    Possible pathways for the pyrolysis of resorcinol with the formation of CO and CO2 as final products were proposed and evaluated using ab initio calculations. Our experimental study revealed that large quantities of CO2 are generated in the pyrolysis of 1,3-dihydroxybenzene (resorcinol), while the pyrolysis of the dihydroxybenzene isomers 1,2-dihydroxybenzene (catechol) and 1,4-dihydroxybenzene (hydroquinone) produces little CO2. The fate of oxygen atoms in catechol and hydroquinone was essentially the formation of CO. In the proposed pathways, the triplet ground state m-benzoquinone was generated initially from simultaneous cleavage of the two O-H bonds in resorcinol. Subsequently, the direct cleavage of a C-C bond of the m-benzoquinone diradical yields 2-oxidanylcyclopenta-2,4-dien-1-yl-methanone, which can be converted via two channels: release of CO from the aldehyde radical group and combination of the ketone radical and carbon atom in the aldehyde radical group to form the 6-oxabicyclo[3.2.0]hepta-2,4-dien-7-one, resulting in the release of CO2. Potential energy surfaces along the proposed reaction pathways were calculated employing the CBS-QB3 method, and the rate constants at the high-pressure limit were also evaluated based on transition-state theory to assess the feasibility of the proposed reaction pathways.

  14. Understanding natural semiquinone radicals--multifrequency EPR and relativistic DFT studies of the structure of Hg(II) complexes.

    Witwicki, Maciej; Jerzykiewicz, Maria; Ozarowski, Andrzej


    Multifrequency EPR spectroscopy and DFT calculations were used to investigate Hg(II) complexes with semiquinone radical ligands formed in a direct reaction between the metal ions and tannic acid (a polyphenol closely related to tannins). Because of the intricate structure of tannic acid a vast array of substituted phenolic compounds were tested to find a structural model mimicking its ability to react with Hg(II) ions. The components of the g matrix (the g tensor) determined from the high field (208 GHz) EPR spectra of the Hg(II) complexes with the radical ligands derived from tannic acid and from the model compounds were analogous, indicating a similar coordination mode in all the studied Hg(II) complexes. Since catechol (1,2-dihydroxybenzene) was the simplest compound undergoing the reaction with Hg(II) it was selected for DFT studies which were aimed at providing an insight into the structural properties of the investigated complexes. Various coordination numbers and different conformations and protonation states of the ligands were included in the theoretical analyses. g Matrices were computed for all the DFT optimized geometries. A good agreement between the theoretical and experimental values was observed only for the model with the Hg(II) ion tetracoordinated by two ligands, one of the ligands being monoprotonated with the unpaired electron mainly localized on it.

  15. Organic impurity profiling of 3,4-methylenedioxymethamphetamine (MDMA) synthesised from catechol.

    Heather, Erin; Shimmon, Ronald; McDonagh, Andrew M


    This work examines the organic impurity profile of 3,4-methylenedioxymethamphetamine (MDMA) that has been synthesised from catechol (1,2-dihydroxybenzene), a common chemical reagent available in industrial quantities. The synthesis of MDMA from catechol proceeded via the common MDMA precursor safrole. Methylenation of catechol yielded 1,3-benzodioxole, which was brominated and then reacted with magnesium allyl bromide to form safrole. Eight organic impurities were identified in the synthetic safrole. Safrole was then converted to 3,4-methylenedioxyphenyl-2-propanone (MDP2P) using two synthetic methods: Wacker oxidation (Route 1) and an isomerisation/peracid oxidation/acid dehydration method (Route 2). MDMA was then synthesised by reductive amination of MDP2P. Thirteen organic impurities were identified in MDMA synthesised via Route 1 and eleven organic impurities were identified in MDMA synthesised via Route 2. Overall, organic impurities in MDMA prepared from catechol indicated that synthetic safrole was used in the synthesis. The impurities also indicated which of the two synthetic routes was utilised.

  16. Electrochemistry Experiments to Develop Novel Sensors for Real-World Applications

    Suzanne Lunsford


    Full Text Available These novel STEM (Science Technology Engineering and Mathematics Electrochemistry experiments have been designed to increase the integrated science content, pedagogical, and technological knowledge for real-world applications. This study has focused on (1 the fundamental understanding on the relationship of metal oxide films and polymers to electrochemical sensors, and (2 the development of new materials which have great application of electrode materials. Following the inquiry based learning strategy the research students learn to develop and study the electrode surfaces to meet the needs of stability and low detection limits. Recently, new advances in environmental health are revealing the anthropogenic or naturally occurring harmful organic chemicals in sources of water supply expose a great health threat to human and aquatic life. Due to their well-known carcinogenic and lethal properties, the presence of human produced toxic chemicals such as phenol and its derivatives poses a critical threat to human health and aquatic life in such water resources. In order to achieve effective assessment and monitoring of these toxic chemicals there is a need to develop in-situ (electrochemical sensors methods to detect rapidly. Electrochemical sensors have attracted more attention to analytical chemist and electrochemistry engineers due to its simplicity, rapidness and high sensitivity. However, there will be real challenges of achieving successful analysis of chemicals (phenol in the presence of common interferences in water resources, which will be discussed regarding the students challenging learning experiences in developing an electrochemical sensor. The electrochemical sensor developed (TiO2 , ZrO2 or sol-gel mixture TiO2/ZrO2 will be illustrated and the successes will be shown by cyclic voltammetry data in detection of 1,2-dihydroxybenzenes (catechol, dopamine and phenol.

  17. Adsorption and detection of some phenolic compounds by rice husk ash of Kenyan origin.

    Mbui, Damaris N; Shiundu, Paul M; Ndonye, Rachel M; Kamau, Geoffrey N


    Rice husk ash (RHA) obtained from a rice mill in Kenya has been used as an inexpensive and effective adsorbent (and reagent) for the removal (and detection) of some phenolic compounds in water. The abundantly available rice mill waste was used in dual laboratory-scale batch experiments to evaluate its potential in: (i) the removal of phenol, 1,3-dihydroxybenzene (resorcinol) and 2-chlorophenol from water; and (ii) the detection of 1,2-dihydroxybenzene (pyrocatechol) and 1,2,3-trihydroxybenzene (pyrogallol) present in an aqueous medium. The studies were conducted using synthetic water with different initial concentrations of the phenolic compounds. The effects of different operating conditions (such as contact time, concentration of the phenolic compounds, adsorbent quantity, temperature, and pH) were assessed by evaluating the phenolic compound removal efficiency as well as the extent of their color formation reactions (where applicable). RHA exhibits reasonable adsorption capacity for the phenolic compounds and follows both Langmuir and Freundlich isotherm models. Adsorption capacities of 1.53 x 10(-4), 8.07 x 10(-5), and 1.63 x 10(-6) mol g(-1) were determined for phenol, resorcinol and 2-chlorophenol, respectively. Nearly 100% adsorption of the phenolic compounds was possible and this depended on the weight of RHA employed. For the detection experiments, pyrocatechol and pyrogallol present in water formed coloured complexes with RHA, with the rate of colour formation increasing with temperature, weight of RHA, concentration of the phenolic compounds and sonication. This study has proven that RHA is a useful agricultural waste product for the removal and detection of some phenolic compounds.

  18. The extent of fermentative transformation of phenolic compounds in the bioanode controls exoelectrogenic activity in a microbial electrolysis cell.

    Zeng, Xiaofei; Collins, Maya A; Borole, Abhijeet P; Pavlostathis, Spyros G


    Phenolic compounds in hydrolysate/pyrolysate and wastewater streams produced during the pretreatment of lignocellulosic biomass for biofuel production present a significant challenge in downstream processes. Bioelectrochemical systems are increasingly recognized as an alternative technology to handle biomass-derived streams and to promote water reuse in biofuel production. Thus, a thorough understanding of the fate of phenolic compounds in bioanodes is urgently needed. The present study investigated the biotransformation of three structurally similar phenolic compounds (syringic acid, SA; vanillic acid, VA; 4-hydroxybenzoic acid, HBA), and their individual contribution to exoelectrogenesis in a microbial electrolysis cell (MEC) bioanode. Fermentation of SA resulted in the highest exoelectrogenic activity among the three compounds tested, with 50% of the electron equivalents converted to current, compared to 12 and 9% for VA and HBA, respectively. The biotransformation of SA, VA and HBA was initiated by demethylation and decarboxylation reactions common to all three compounds, resulting in their corresponding hydroxylated analogs. SA was transformed to pyrogallol (1,2,3-trihydroxybenzene), whose aromatic ring was then cleaved via a phloroglucinol pathway, resulting in acetate production, which was then used in exoelectrogenesis. In contrast, more than 80% of VA and HBA was converted to catechol (1,2-dihydroxybenzene) and phenol (hydroxybenzene) as their respective dead-end products. The persistence of catechol and phenol is explained by the fact that the phloroglucinol pathway does not apply to di- or mono-hydroxylated benzenes. Previously reported, alternative ring-cleaving pathways were either absent in the bioanode microbial community or unfavorable due to high energy-demand reactions. With the exception of acetate oxidation, all biotransformation steps in the bioanode occurred via fermentation, independently of exoelectrogenesis. Therefore, the observed

  19. Effects of the co-carcinogen catechol on benzo(a)pyrene metabolism and DNA adduct formation in mouse skin

    Melikian, A.A.; Leszczynska, J.M.; Hecht, S.S.; Hoffmann, D.


    We have studied the effects of the co-carcinogen catechol (1,2-dihydroxybenzene) on the metabolic activation of (/sup 3/H) benzo(a)pyrene (BaP) in mouse skin, in vivo and on the binding of BaP metabolites to DNA and protein at intervals from 0.5-24 h. Upon topical application of 0.015 mg (/sup 3/H)BaP and 0.25 or 0.5 mg catechol per mouse, catechol had little effect on the total amount of (/sup 3/H)BaP metabolized in mouse skin, but it affected the relative proportions of (/sup 3/H)BaP metabolites. Catechol (0.5 mg/mouse) decreased the proportion of water-soluble (/sup 3/H)BaP metabolites, ethyl acetate-soluble polar metabolites and quinones, but doubled the levels of unconjugated 3-hydroxy-BaP at all measured intervals after treatment. Catechol also caused a small increase in the levels of trans-7,8-dihydroxy-7,8-dihydroBaP and trans-9,10-dihydroxy-9,10-dihydroBaP 0.5 h after treatment. Two hours after treatment, the levels of these metabolites subsided to those of the controls. Catechol did not affect the levels of glutathione conjugates of BaP. However, it caused a decrease in glucuronide and sulphate conjugate formation from BaP. Catechol caused an approximately 2-fold increase in the formation of anti-7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydroBaP (BPDE) DNA adducts and elevated the ratio of anti-syn-BPDE-DNA adducts 1.6 to 2.9-fold. Catechol treatment increased the radioactivity associated with epidermal proteins after (/sup 3/H)BaP application. Because catechol increased levels of 3-hydroxyBaP, we considered the possibility that 3-hydroxyBaP might enhance the tumor initiating activities of BaP or BPDE in mouse skin; a bioassay demonstrated that this was not the case. The results of this study indicate that one important effect of catechol related to its co-carcinogenicity is its ability to enhance formation of anti-BPDE-DNA adducts in mouse skin.

  20. Cytotoxic effects of catechols to glial and neuronal cells

    Ramon Santos El-Bachá


    Full Text Available Catechols are compounds that autoxidises under physiological conditions leading to the formation of reactive oxygen species (ROS, semiquinones, and quinones. These molecules can be formed in organisms because of the metabolism of exogenous aromatic substances, such as benzene. However, there are several important endogenous catechols, which have physiological functions, such as catecholamines. Furthermore, several pharmacological agents are catechols, such as apomorphine, or can be metabolised to generate these compounds. In this presentation we will show that apomorphine can unspecifically bind to proteins during its autoxidation, a phenomenon that is inhibited by thiols. Brain endothelial cells and glial cells express xenobiotic-metabolising enzymes as components of the metabolic blood-brain barrier in an attempt to protect the central nervous system against drugs. Since UDP-glucuronosyltransferases (EC are among these enzymes, we investigated the ability of brain microsomes to conjugate catechols with glucuronate. Despite the fact that 1-naphtol could be glucuronidated in the presence of brain cortex microsomes, the same was not observed for most of catechols that were tested. Therefore, this is not the main mechanism used to protect the brain against them. Indeed, catechols may inhibit other xenobiotic-metabolising enzymes. We showed that apomorphine inhibited the cytochrome P450-dependent dealkylation activity. The production of ROS and reactive quinones, as well as their effects on protein functions, seems to be involved in the cytotoxicity of catechols. Glial cells are more resistant than neuronal cells. Apomorphine was more toxic to rat neurons than to rat C6 glioma cells. 1,2-Dihydroxybenzene (catechol killed human GL-15 cells with an EC50 of 230 uM after 72 h, a effect that was significantly inhibited by superoxide dismutase (EC Another mechanism that we found to be involved in catechol cytotoxicity is the inhibition

  1. Catechol inhibits FADH2-linked respiration in rat liver mitochondrial fraction Catecol inibe FADH2 ligado à respiração na fração mitochondrial do fígado do rato

    George Emílio Sampaio Barreto


    Full Text Available PURPOSE: The aim of this work was to investigate the hypothesis that catechol inhibits FADH2-linked basal respiration in mitochondria isolated from rat liver homogenates. Moreover, catechol ability to induce peroxidation of biomolecules in liver nuclear fractions was also studied. METHODS: Rat liver homogenates were incubated with 1mM 1,2-dihydroxybenzene (catechol at pH 7.4 for up to 30 minutes. After that, mitochondrial fractions were isolated by differential centrifugation. Basal oxygen uptake was measured using a Clark-type electrode after the addition of 10 mM sodium succinate. Nuclear fractions were incubated in the presence of 1 mM catechol for 17 hours at room temperature and the peroxidation of biomolecules was investigated by the reaction with thiobarbituric acid, which was determined spectrophotometrically at 535 nm. RESULTS: Catechol induced a time-dependent partial inhibition of FADH2-linked basal mitochondrial respiration, however this substance was unable to induce a direct peroxidation of biomolecules in hepatic nuclear fractions. CONCLUSION: Catechol produced an inhibition of basal respiration associated to FADH2 in isolated liver mitochondria that could lead to cytotoxicity, ROS generation and cell death.OBJETIVO: Testar a hipótese do catecol inibir a respiração basal associada ao FADH2 em frações mitocondriais hepáticas de rato. Além disso, estudou-se também a capacidade do catecol de induzir peroxidação de biomoléculas nas frações nucleares. MÉTODOS: Os homogeneizados de fígado de ratos foram incubados com catecol a 1 mM em pH fisiológico. Depois disso, as frações mitocondriais foram isoladas por centrifugação diferencial. O consumo basal de oxigênio foi medido com um eletrodo do tipo Clark após injeção de succinato a 10 mM. Frações nucleares foram incubadas com catecol por 17 horas à temperatura ambiente e a peroxidação de biomoléculas foi investigada pela reação com o ácido tiobarbitúrico e

  2. Coordination chemistry of microbial iron transport compounds. IX. Stability constants for catechol models of enterobactin

    Avdeef, A.; Sofen, S.R.; Bregante, T.L.; Raymond, K.N.


    The stability constants of ferric complexes with several substituted catechol (1,2-dihydroxybenzene) ligands in aqueous solutions of low ionic strength have been determined at 27/sup 0/C in the pH range 2 to 11. Enterobactin, the principal siderophore of enteric bacteria, is a tricatechol and, from the formation constants reported here, is estimated to have a formation constant with ferric ion which is greater than 10/sup 45/. The stepwise formation constants, K/sub n/, of the catechol ligands reported here are defined as (ML/sub n/)/(ML/sub n-1/)(L), in units of L mol/sup -1/, where (L) is the concentration of the deprotonated catechol ligand. The constants were determined from potentiometric and spectroscopic data and were refined on pH values by weighted least squares. Qualitative examination of electron spin resonance spectra of the systems indicated some oxidation of the ligand by ferric ions at pH values as high as 4. The ligands studied included catechol (cat) (log K/sub 1/ = 20.01, log K/sub 2/ = 14.69, log K/sub 3/ = 9.01); 4,5-dihydroxy-m-benzenedisulfonate (Tiron) (log K/sub 2/ = 15.12, log K/sub 3/ = 10.10); 4-nitrocatechol (ncat) (log K/sub 1/ = 17.08, log K/sub 2/ = 13.43, log K/sub 3/ = 9.51); 3,4-dihydroxyphenylacetic acid (dhpa) (log K/sub 1/ = 20.1, log K/sub 2/ = 14.9, log K/sub 3/ = 9.0); and 2,3-dihydroxybenzoic acid (dhba) (log K/sub 1/ = 20.5). The acid dissociation constants, K/sub a/s, were determined also. For the catechol protons these follow: cat (pK/sub a/sub 1// = 9.22, pK/sub a/sub 2// = 13.0); Tiron (pK/sub a/sub 1// = 7.70, pK/sub a/sub 2// = 12.63); ncat (pK/sub a/sub 1// = 6.65, pK/sub a/sub 2// = 10.80); dhpa (pK/sub a/sub 1// = 9.49, pK/sub a/sub 2// = 13.7); and dhba (pK/sub a/sub 1// = 10.06, pK/sub a/sub 2// = 13.1). In addition, carboxylate substituents of dhpa and dhba have pK/sub a/s of 4.17 and 2.70, respectively.In solution, exchange is slow between these two types of coordination following changes in pH. 2 tables, 11