SEARCH · PubMed Health

Results for “PYROCATECHOL”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9Linked to original sources

PubMed1997

Speciation of aluminium in tea infusions studied by size exclusion chromatography with detection by post-column reaction.

Aluminium-organic species in tea infusions were studied by size exclusion chromatography, using a Superose 12 HR column, a mobile phase of 0.12 mol l-1 tris(hydroxymethyl)aminomethane adjusted to pH 5.5 and detection by UV-visible spectrophotometry. Aluminium was detected after post-column reaction with pyrocatechol violet at 585 nm and the organic material was detected at 280 nm. Teas of different origin were analyzed; the results indicate that aluminium is bound to the same relatively narrow size-range of large organic molecules in the tea infusions, irrespective of the origin of the tea.

Aluminum↗

PubMed1979

Osmiophilic reagents in electronmicroscopic histocytochemistry.

Direct histocytochemical staining methods on undisrupted tissues, stabilized by chemical fixation, potentially offer perhaps the most reliable approach to the study of the enzymes of the cell with relation to its ultrastructure. The atoms which, for the most part, comprise the biomacromolecules and enzymes of cells and tissues contribute little to their inherent electron opacity or ability to scatter electrons differentially. The latter property of a substance is responsible for its observation with the electron microscope. Since the introduction of osmiophilic reagents into cytochemistry (HANKER et al. 1964), the selective deposition of relatively large amounts of polymeric osmium black reaction products at the subcellular sites of insoluble or immobilized enzymes or biomacromolecules has facilitated their demonstration with the light and electron microscopes. Perhaps the most widely employed osmiophilic reagent in histocytochemistry has been DAB which was introduced by GRAHAM and KARNOVSKY (1966a, b). Although it receives its widest use for demonstrating the sites to which the exogenous ultrastructural tracer horseradish peroxidase (HRP) is transported in vertebrate tissues, it is also widely employed for the demonstration of catalase in peroxisomes with the media of FAHIMI (1969) or of NOVIKOFF and GOLDFISCHER (1969), and for the demonstration of cytochrome oxidase with the medium of SELIGMAN et al. (1968a). The importance of this reagent lies in its ability to undergo oxidative polymerization forming an insoluble osmiophilic melanin-like product (HANKER et al. 1972a) which comforms well to ultrastructure, at the sites of enzymic or nonenzyme proteins which catalyze its oxidation. In the past few years, studies in our laboratory have shown that a rational approach to the histocytochemical demonstration of enzymes could be devised. It is based on the selective deposition of transition metal compounds at the sites of enzymes that resemble hemoproteins in their ability to catalyze the oxidative polymerization of DAB. The most useful of these compounds, cupric ferrocyanide (Hatchett's brown) was also introduced into cytochemistry by Karnovsky's laboratory (KARNOVSKY 1964; KARNOVSKY and ROOTS 1974). By the use of natural substrates, when available, or synthetic substrates which liberate or form a reducing agent at the sites of the enzymatic activity, many diverse types of enzymes have been demonstrated by methods depending on this principle known as catalytic osmiophilic polymer generation. DAB has probably been the most useful histocytochemical reagent of the past decade. Yet its borderline carcinogenicity and the frequent interruption of a supply of good quality DAB have encouraged research into a substitute reagent. A new substitute for DAB has resulted from the study of artificial melanins in our laboratory for several years. It consists of a mixture of p-phenylenediamine and pyrocatechol and is much better than DAB for the demonstration of HRP used as a cytochemical tracer...

3,3'-Diaminobenzidine↗

PubMed2001

A new sensitive and selective spectrophotometric method for the determination of catechol derivatives and its pharmaceutical preparations.

A sensitive and simple spectrophotometric method for the estimation of certain catechol derivatives like pyrocatechol (PCL), dopamine hydrochloride (DPH), levodopa (LDP), methyl dopa (MDP) and adrenaline (ADH) in either pure form or in its pharmaceutical formulation is described. The method is based on the interaction of diazotised p-nitro aniline (DPNA) with catechol derivatives in presence of molybdate ions in acidic medium. Absorbance of the resulting red complex is measured at 500-510 nm, respectively, and is stable for 2-10 h. The method is highly reproducible and specific for these selected catechol derivatives. The common excipients used as additives in pharmaceuticals and phenol, hydroquinone, resorcinol, pyrogallol and phloroglucinol do not interfere in the proposed method. Analytical data for determination of the pure compound is presented together with the application of the proposed method to the analysis of some pharmaceutical formulations. The results compare favourably with those of official and reported methods.

Catechols↗

PubMed1998

Use of sensitized luminescence of lanthanides in analysis of drugs.

The sensitization of the Tb(III) and Eu(III) ions luminescence by drugs, the pyrocatechol, naphthyridine and heterocyclic aromatic acid derivatives, were studied. It was shown that a result of intramolecular energy transfer from the ligand molecule to the lanthanide ion increases the luminescence intensity of the latter by 10(8)-10(10) times. The luminescence properties of the complexes in solutions were investigated. The highly sensitive methods for luminescence determination of dopegyt, levodopum, dophaminum, nevigramon, furosemidum and cinchophenum were developed. The detection limits of the drugs are 0.0005, 0.02, 0.5, 0.01, 0.05 and 0.1, respectively.

Acids, Heterocyclic↗

PubMed2003

Visual detection of AMP and real-time monitoring of cyclic nucleotide phosphodiesterase (PDE) activity in neutral aqueous solution. Chemosensor-coupled assay of PDE and PDE inhibitors.

A phosphate chemosensor ensemble, [Zn(H-bpmp)(pyrocatechol violet)](+) is useful for a real-time assay of phosphodiesterases (PDEs) in a neutral aqueous solution. In addition, a simple and convenient screen and assay procedures for inhibitors of PDEs have been demonstrated using IBMX, a nonselective PDE inhibitor as an example.

1-Methyl-3-isobutylxanthine↗

PubMed1997

Tract-tracing in the nervous system of vertebrates using horseradish peroxidase and its conjugates: tracers, chromogens and stabilization for light and electron microscopy.

Surprisingly the first generation of tract-tracing techniques based on intra-axonal transport, that is the methods utilizing the uptake and transport of horseradish peroxidase (HRP), still rank among the most widely used neuroanatomical tracing techniques. The success of these methods can be ascribed to several characteristics. They are fast and easy to implement. Complicated injection apparatus is unnecessary. The reaction products are visualized through simple histochemical reactions, and they are permanent or can be stabilized into permanency. Most usefully, the reaction products are visible in the light and electron microscopes. HRP (mol. wt. 44 kDa) is extracted from the roots of the horseradish plant (Cochlearia armoracia L.). Uptake of HRP into cells occurs via a passive process of endocytosis. Since lectins like wheat germ agglutinin (WGA) and bacterial toxin fragments (subunit B of cholera toxin (CTB)) strongly induce active, receptor-mediated uptake mechanisms, conjugates of these substances with HRP have been successfully applied in sensitive tract-tracing HRP and its conjugates are transported both in anterograde and retrograde direction. Retrograde transport occurs in small vesicles that are incorporated in lysosome-like vacuoles and in the Golgi apparatus. These vesicles differ in membrane properties from the anterogradely transported HRP vesicles. The retrogradely transported vesicles tend to fuse and thus accumulate HRP at high densities, facilitating the visibility of the final reaction product. The anterogradely transported HRP does not accumulate directly in lysosome-like bodies and is distributed diffusely and therefore often requires specific visualization methods. HRP and WGA-HRP may therefore be used in anterograde and retrograde transneuronal (multineuron) transport studies. Even in fixed material, labeling through diffusion of HRP can provide details on neural connections. Visualization of transported HRP is achieved by means of using the oxidative enzymatic activity of HRP to precipitate a chromogen according to the following reaction: [symbol: see text] The final reaction product may be soluble in buffer or ethanol and may require stabilization to prevent fading. In this protocol we discuss the widely used chromogens 3,3'-diaminobenzidine tetrahydrochloride (DAB), 3,3',5,5'-tetramethylbenzidine (TMB), benzidine dihydrochloride (BDHC) and p-phenylenediamine dihydrochloride with pyrocatechol (PPD-PC). Other possible chromogens, not discussed here, are 4-chloro-1-naphthol (4C1N), 3-amino-9-ethylcarbazole (AEC) and o-phenylenediamine (OPD). The visualization of the reaction product can be further improved by intensification with metal salts. At the light microscopic level (LM) this intensification enables color differentiation between distinct markers. In the present protocol we provide an up-to-date guideline for the application of HRP and its conjugates in tracing with special emphasis on electron microscopic (EM) visualization. Some modifications for stabilization and of metal intensification to enhance visibility are incorporated in conjunction with specific methods for multiple labeling in combined tract-tracing experiments.

Animals↗

PubMed1985

Affinity-dependent cross-linking to neurotoxin sites of the acetylcholine receptor mediated by catechol oxidation.

The choline homologue 3-[(trimethylammonio)methyl]catechol (TMC) has been synthesized, and the controllable features of its complex oxidation have been examined spectroscopically and correlated with its toxin binding inactivating reactions with the acetylcholine receptor (AcChR) from Torpedo californica electroplax. Affinity-dependent reactions of early intermediates in the oxidation of TMC are suggested to intercede covalently in this inactivation. At pH 7.4, where the oxidative polymerization of catechols proceeds spontaneously, pyrocatechol produced no effect on the toxin binding function of AcChR, whereas comparable concentrations of TMC led to inactivation of half of all available sites. Lower concentrations of TMC converted via oxidation with ceric salts to an in situ mixture of monohydroxylated catechols were shown to be effective in short-term incubations in inactivating approximately half of the toxin binding sites by covalent labeling of the receptor. Mixtures of dihydroxycatechol intermediates, hydroxy-p-quinones, and polymeric products led to nonspecific toxin binding site inactivation of AcChR in excess of half of all available sites. Collectively, the results suggest that both covalent labeling and oxygen reduction product inactivating mechanisms are operative in these model macromolecular site reactions and that catechol-containing affinity reagents may be useful in elucidating the molecular features of sites to which they are directed.

Animals↗

PubMed2002

Fractionation and determination of aluminum and iron in soil water samples using SPE cartridges and ICP-AES.

The use of commercially available solid phase extraction (SPE) cartridges for the fractionation of Al and Fe in soil water is described. The quantitative determination was done by inductively coupled plasma atomic emission spectrometry (ICP-AES). Different types of SPE cartridges, based on cation exchange, anion exchange, and chelation were studied. To avoid pH changes, the SPE cartridge should be conditioned with a buffer that has a pH close to that of the sample. Both strong cation exchange (SCX) and chelation were found to work well, whereas low recovery was observed for Al when anion exchange was used. For Fe, the sum of the anionic and cationic fractions that passed through the cartridges was nearly 100%. The results obtained for Al for 23 soil water samples using a SPE/SCX cartridge and ICP-AES were compared with equilibrium calculations using the program ALCHEMI and also with a fractionation method that was based on separation on a manually prepared SCX column and detection by molecular spectrophotometry, after complexation with pyrocatechol violet (SCX-PCV method). The SPE/SCX-ICP-AES results for the labile Al fraction (Al bound to the SCX cartridge) showed an acceptable correlation with the results obtained by the equilibrium calculations, except for the samples with the highest DOC concentrations, whereas the values obtained for labile Al by the more traditional SCX-PCV method were much lower. We recommend that the SPE/SCX-ICP-AES procedure described in this work be selected for the fractionation of Al and Fe species in soil and freshwater samples.

Aluminum↗

PubMed2003

Environmental ice photochemistry: monochlorophenols.

Photolysis of 2- and 4-chlorophenol samples in water ice of the initial concentrations 10(-7) to 10(-2) mol L(-1) is reported. Major phototransformations appeared to be based on the coupling reactions due to chlorophenol aggregation at the grain boundaries of the polycrystalline state. The main products, chlorobiphenyldiols, belong to the family of phenolic halogenated compounds (such as hydroxylated polychlorobiphenyls) that are known xenobiotics found in nature. No photosolvolysis products, that is products from intermolecular reactions between organic and water molecules, were observed at temperatures below -10 degrees C. Raising the temperature to -5 degrees C caused a moderate photosolvolytic activity in the case of 4-chlorophenol (formation of hydroquinone), in contrast to 2-chlorophenol which was almost exclusively transformed into pyrocatechol. It is suggested that photosolvolysis above this temperature occurs in a liquid or quasi-liquid layer that covers the ice crystal surfaces. The results support our model in which significant amounts of some persistent, bioaccumulative, and toxic compounds may be generated by photochemistry of primary pollutants in cold ecosystems and in the upper atmosphere, and may be subsequently released to the environment.

Chlorophenols↗

PubMed2005

Diffusive gradients in thin films sampler predicts stress in brown trout (Salmo trutta L.) exposed to aluminum in acid fresh waters.

Increased levels of aluminum ions released from nutrient-poor soils affected by acid rain have been the primary cause of fish deaths in the acidified watersheds of southern Norway. The complex aluminum chemistry in water requires speciation methods to measure the gill-reactive species imposing toxic effects toward fish. Previously, aluminum speciation has mainly followed the fractionation principles outlined by Barnes/Driscoll, and several analogues of these fractionation principles have been used both in situ and in the laboratory. Due to rapid transformation processes, aluminum speciation in water samples may change even during short storage times. Thus, results obtained by laboratory fractionation methods might be misleading for the assessment of potentially toxic aluminum species in the water. Until now, all in situ field fractionation methods have been time and labor consuming. The DGT technique (diffusive gradients in thin films) is a new in situ sampler collecting a fraction of dissolved metal weighted according to the rate of diffusion and dissociation kinetics. In a field experiment with acid surface water we studied the DGT sampler as a new prediction tool for the gill accumulation of aluminum in trout (Salmo trutta L.) and the induced physiological stress responses measured as changes in blood glucose and plasma chloride. Aluminum determined with DGT (DGT-AI) was higher than labile monomeric aluminum (Ali) determined with a laboratory aluminum fractionation procedure (PCV--a pyrocatechol violet analogue of Barnes/Driscoll), a difference due to collection of a fraction of organically complexed aluminum by DGT and a reduction of the Ali fraction during sample storage. DGT-AI predicted the gill uptake and the aluminum-induced physiological stress responses (increased blood glucose and decreased plasma chloride, r2 from 0.6 to 0.9). The results indicate that DGT-AI is a better predictor for the stress response than laboratory-determined Ali, because the DGT sampler collects a more correct fraction of the gill-reactive aluminum species that induces the stress.

Aluminum↗

PubMed2005

Phenol degradation by a nonpulsed diaphragm glow discharge in an aqueous solution.

In the present study, a nonpulsed direct current diaphragm glow discharge process was developed for the first time for phenol degradation in an aqueous solution. The discharge was generated in a small hole in a dielectric diaphragm interposed between two submersed graphite electrodes. The experimental results revealed that supplied voltage, initial pH, iron salts, and radical scavengers impact the phenol degradation significantly. Enhancing the applied voltage, lowering the solution pH, and adding appropriate amounts of Fe2+ or Fe3+ to the solution were found to be favorable for phenol degradation. Carbonate ions or n-butanol in the solution can decelerate the phenol removal. When the treatment time is increased, the pH value of the solution decreased, leading to an increase in the phenol decomposition. It was revealed by high performance liquid chromatography and ionic chromatography that the main intermediates of phenol decomposition are hydroquinone, pyrocatechol, p-benzoquinone and organic acids. In comparison with the high-voltage corona discharge plasma in distilled water, this process offers simple technology, higher energy efficiency, easier scaleup, and easier applicability to salt-containing wastewater with no electrode erosion and electromagnetic radiation.

Chromatography, High Pressure Liquid↗

PubMed2005

Aminoparathion: a highly reactive metabolite of parathion. 1. Reactions with polyphenols and polyphenol oxidase.

Spiking of tomato and apple fruits with parathion at different levels of about 1-4 mg/kg irradiation and under simulated sunlight conditions resulted in nearly complete photodegradation within 13 h, but extractable parathion degradation products could not be found in any case. However, after irradiation of an unrealistically spiked apple (134 mg/kg) different photoproducts including aminoparathion (AP) were detectable by HPLC, proving that the hitherto postulated photochemistry of parathion indeed takes place in the fruit cuticle environment. Besides the photoreduction pathway it was shown for the first time that AP is also easily formed by reduction of the primary photoproduct nitrosoparathion with thiols (cysteine, glutathione), while ascorbic acid only leaves hydroxylaminoparathion. In the presence of polyphenols, AP was effectively bound to quinone intermediates formed by both silver oxide and polyphenol oxidases. For pyrocatechol, a disubstituted o-quinone derivative could be isolated as a dark red addition product and structurally be elucidated. However, in the presence of caffeic acid, catechol, naringin, and quercetin, respectively, insoluble dark colored polymers precipitated within 48 h, while in the supernatants AP was not detectable any more. Polymer-bound and nonextractable AP was proven by transesterification with sodium ethoxide releasing O,O,O-triethyl thiophosphate which was determined by GC. Additionally, AP itself was a substrate for polyphenol oxidases, resulting in a quinone imine intermediate which in turn reacted with excessive AP yielding deep red colored di- and trimerization products.

Catechol Oxidase↗

PubMed1992

Dihydroxynitrobenzaldehydes and hydroxymethoxynitrobenzaldehydes: synthesis and biological activity as catechol-O-methyltransferase inhibitors.

A series of nitro derivatives of dihydroxy- and hydroxymethoxybenzaldehyde was synthesized and tested as potential inhibitors of partially purified pig liver catechol-O-methyltransferase (COMT). All the dihydroxynitrobenzaldehydes prepared were potent inhibitors of COMT, but only one hydroxymethoxynitrobenzaldehyde (3-hydroxy-4-methoxy-5-nitrobenzaldehyde) showed activity as a COMT inhibitor. Although previously reported data showed that the presence of electron-withdrawing substituents at position 5 seemed to be very important for activity as COMT inhibitor, our results suggest that the requirement necessary to enhance the activity of the dihydroxyni-trobenzaldehyde derivatives toward COMT is the presence of the nitro group in a position ortho with respect to one hydroxyl group. The assayed compounds showed a reversible inhibition of COMT, which was mixed for all the dihydroxynitro derivatives but noncompetitive for 3-hydroxy-4-methoxy-5-nitrobenzaldehyde when pyrocatechol was the variable substrate and uncompetitive in all the inhibitors with respect to S-adenosyl-L-methionine.

Animals↗

PubMed2003

Bromophenols from the red alga Rhodomela confervoides.

Six new bromophenols, 3-bromo-4,5-bis(2,3-dibromo-4,5-dihydroxybenzyl)pyrocatechol (1), 2,2',3-tribromo-3',4,4',5-tetrahydroxy-6'-hydroxymethyldiphenylmethane (2), 2,2',3-tribromo-3',4,4',5-tetrahydroxy-6'-ethyloxymethyldiphenylmethane (3), (+/-)-2-methyl-3-(2,3-dibromo-4,5-dihydroxyphenyl)propylaldehyde (4), (+/-)-2-methyl-3-(2,3-dibromo-4,5-dihydroxyphenyl)propylaldehyde dimethyl acetal (5), and 3-bromo-4,5-dihydroxybenzoic acid methyl ester (6), together with eight known bromophenols, 3-bromo-4,5-dihydroxybenzaldehyde (7), 2,3-dibromo-4,5-dihydroxybenzyl alcohol (lanosol, 8), 2,3-dibromo-4,5-dihydroxybenzyl methyl ether (9), 2,3-dibromo-4,5-dihydroxybenzyl ethyl ether (10), 2,3-dibromo-4,5-dihydroxybenzylaldehyde (11), bis(2,3-dibromo-4,5-dihydroxybenzyl) ether (12), 3-bromo-4-(2,3-dibromo-4,5-dihydroxybenzyl)-5-methoxymethylpyrocatechol (13), and 2,2',3,3'-tetrabromo-4,4',5,5'-tetrahydroxydiphenyl methane (14), were isolated from the red alga Rhodomela confervoides. Their structures were elucidated by chemical and spectroscopic methods including IR, HRFABMS, and 1D and 2D NMR techniques.

China↗

PubMed2000

Five phenolic glycosides from Alangium chinense.

From the dried leaves of Alangium chinense, five novel phenolic glycosides, 6'-O-galloylsalicin (1); 4',6'-di-O-galloylsalicin (2); 4',6'-O-(S)-hexahydroxydiphenoylsalicin (3); 4', 6'-O-(R)-hexahydroxydiphenoylsalicin (4); and pyrocatechol 1-O-beta-D-xylopyranosyl(1-->6)-beta-D-glucopyranoside (5) were isolated. The structures of these new compounds were determined by spectroscopic methods.

Carbohydrate Conformation↗

PubMed2006

A colorimetric boronic acid based sensing ensemble for carboxy and phospho sugars.

[structure: see text] A cadmium-centered tris-boronic acid receptor was synthesized, and its binding properties toward various anionic sugars were determined. This receptor shows high affinity for different anionic sugars, especially gluconic acid, which has an association constant near approximately 10(7) M(-)(1) at neutral pH. Further, using an indicator displacement assay, a color change of pyrocatechol violet was observed upon addition of anionic sugars. This colorimetric test was used as a facile screening technique to qualitatively analyze guest affinities.

Boronic Acids↗

PubMed2002

Spleen and liver pigmented macrophages of Rana esculenta L. A new melanogenic system?

The present study reports the results of a morpho-functional analysis of spleen pigmented cells from Rana esculenta L. and comparison with liver melanin-synthesizing cells, belonging to the macrophage cell lineage. Cytological and cytochemical analyses show that parenchymal pigmented cells of the spleen, like those of the liver, are positive to peroxidase and lipase reactions and have phagocytic properties. The observation of premelanosomes in various stages of differentiation, together with the demonstration of dopa oxidase activity in the melanosome proteins, indicate that spleen pigmented macrophages have endogenous melanogenic ability as do liver pigmented macrophages. Attempts to demonstrate tyrosinehydroxylase activity in melanosome protein extracts from frog spleen and liver, using the same protocol as for mammalian tyrosinases, gave negative results. As regards the dopa oxidase activity revealed, some of its properties differ from the typical behaviour observed for tyrosinases from different sources. Peroxidase activity is shown in spleen and liver melanosome proteins with p-phenylenediamine-pyrocatechol (PPD-PC), and not with typical peroxidase substrates. Suitable inhibition tests revealed that dopa oxidase and peroxidase activities might be supported by two different proteins. Liver melanosome extracts display a very strong laccase (dimethoxyphenoloxidase) activity but spleen extracts do not. Differences observed in the enzymatic properties of the spleen and liver melanosomes suggest that pigmented macrophages may undergo tissue-specific differentiation. These preliminary data show that the melanin pathway of pigmented macrophages is different from that of melanocytes and may pave the way to identification of a new melanogenic pathway in vertebrates.

Animals↗

PubMed2000

Comparison study of five analytical methods for the fractionation and subsequent determination of aluminium in natural water samples.

Five methods for aluminium fractionation used in different laboratories in Norway and Finland were compared using six control, 75 soil water and 10 lake water samples. Different fractionation principles [cation exchange, formation of the Pyrocatechol Violet (PCV) or quinolin-8-ol (oxine) complex], types of cation exchanger [Amberlite (Na/H) or Bond Elut (H)], reaction time (from 2.3 s), flow systems (flow injection analysis or segmented flow) and determination principles (molecular absorption spectrometry or ICP-AES) were tested. Determination of the 'labile' fraction was strongly dependent on the method used and the largest differences were observed between the ICP-AES method with cation exchange (Bond Elut H form) and the 'quickly reacting' method (oxine, 2.3 s). Different flow systems, both using cation exchange and determination of the PCV complex but with different reaction times and an extra acidification step, resulted in large differences in the 'reactive' and 'non-labile' fractions determined. However, the determination of the labile fraction gave similar results with both these methods. The two different types of cation exchanger used (with and without pH buffering and with different counter ions) in the ICP-AES methods resulted in differences, mainly because of a smaller 'non-labile' fraction in the non-buffered system. The two flow injection systems (oxine and PCV complexation) showed common trends, which may be connected with the short reaction times used. Comparison with theoretical equilibrium calculations using the model ALCHEMI suggested that the best correlation for the determination of the 'labile' fraction were obtained with the ICP-AES method with an Amberlite column.

Aluminum↗