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At least 19 recordsLinked to original sources

PubMed2003

Study and analytical application of ion-pair formation in the system fluoxetine-pyrocatechol violet and fluvoxamine-pyrocatechol violet.

Pyrocatechol violet (PCV) reacts in aqueous media with fluoxetine (FLX) and fluvoxamine (FLV) forming coloured ion-association complexes, which are insoluble in water but quantitatively extracted into chloroform-n-butanol mixture. The composition of the compounds, studied by spectrophotometric methods showed that the molar ratio PCV : FLX and PCV : FLV is 1 : 1. The compounds were characterized by UV-VIS, IR and NMR spectrometry. Under optimal experimental conditions fluoxetine and fluvoxamine were determined in the range 1.3-18.0 microg/ml and 2.6-39.1 microg/ml, respectively. The proposed methods have been succesfully applied to the determination of these drugs in pharmaceuticals and natural samples.

Albumins↗

PubMed1976

The mechanism of inhibition of initiation of protein synthesis in reticulocyte lysates by pyrocatechol violet.

1. Pyrocatechol violet inhibits the initiation of protein synthesis in reticulocyte lysates. It prevents the formation of 80-S initiation complexes by inhibiting the binding of mRNA to 40-S initiation complexes. 2. Pyrocatechol violet inhibits the hydrolysis of methionyl-tRNAmetf by reticulocyte lysates or reticulocyte cell sap. 3. Concentrations of pyrocatechol violet sufficient to inhibit initiation have little effect on amino acid activation. Higher concentrations of pyrocatechol violet were strongly inhibitory.

Animals↗

PubMed2003

Irreversible inhibition of jack bean urease by pyrocatechol.

Pyrocatechol was studied as an inhibitor of jack bean urease in 20 mM phosphate buffer, pH 7.0, 25 degrees C. The inhibition was monitored by an incubation procedure in the absence of substrate and reaction progress studies in the presence of substrate. It was found that pyrocatechol acted as a time- and concentration dependent irreversible inactivator of urease. The dependence of the residual activity of urease on the incubation time showed that the rate of inhibition increased with time until there was total loss of enzyme activity. The inactivation process followed a non-pseudo-first order reaction. The obtained reaction progress curves were found to be time-dependent. The plots showed that the rate of the enzyme reaction in the final stages reached zero. From protection experiments it appeared that thiol-compounds such as L-cysteine, 2-mercaptoethanol and dithiothreitol prevented urease from pyrocatechol inactivation as well as the substrate, urea, and the competitive inhibitor boric acid. These results proved that the urease active site was involved in the pyrocatechol inactivation.

Catechols↗

PubMed2005

[Spectrophotometric simultaneous determination of pyrocatechol, resorcinol and hydroquinone by LM-BP neural network].

By means of artificial neural network and Levenberg Marquardt Back Propagation (LM-BP) train algorithm, the three components of pyrocatechol, resorcinol and hydroquinone were determined simultaneously. The absorption spectra of these three components severely overlap in ultraviolet spectral range. Three wavelengths at 283.5, 279.5 and 276.5 nm were selected for the determination. 25 mixture standard solutions were prepared according to orthogonal projection form L25 (5(6)). Three kinds of components were trained. Mean Squared Error (MSE) reaching minimum value is 0.083 114 3. Meanwhile the contents of pyrocatechol, resorcinol and hydroquinone in six simulation mixture samples were predicted. The relative errors of the three kinds of components were slightly larger under the low concentration condition, and the mean relative error for most analytical results was less than 5%, especially it is satisfactory for the analytical results of pyrocatechol and resorcinol with severely overlapped absorption spectra.

English Abstract↗

PubMed1997

Inhibition of oxidation of aromatic amines in heme-containing hydrogen peroxide systems by substituted 4,6-di-tert-butyl-pyrocatechols.

The substituted pyrocatechols sodium (2,3-dihydroxy-4,6-di-tert-butyl-phenyl)-S-thiosulfate (InH1) and 3-(S-glutathionyl)-4,6-di-tert-butyl-pyrocatechol (InH2) effectively inhibited oxidation of o-phenyle-nediamine and tetramethylbenzidine (TMB) catalyzed by hemin or its complex with BSA (methemalbumin). The method of competitive reactions of aromatic amines (PDA, TMB) and pyrocatechols (InH1, InH2) with active radicals was used for the quantitative determination of rates of radical initiation in systems containing hemin (methemalbumin) and H2O2 (TBHP). The use of the inhibitor method for heme-protein-peroxide systems is complicated by heterogeneity of the radicals generated (HO., RO., HO2., RO2., peroxide-like compounds I and II), formation of complexes of the inhibitors with protein component, and possible interaction of active radicals with organic co-solvents (DMF or DMSO). The system hemin (methemalbumin)-H2O2 (TBHP)-aromatic amines can be used for testing the efficacy of potential bioantioxidants.

Antioxidants↗

PubMed2000

Pyrocatechol Violet Complexation at the Boehmite-Water Interface.

Acid/base reactions and pyrocatechol violet complexation at the boehmite-solution interface have been investigated in 0.10 M K(Cl) solution at 298.2 K in the range 5.0</=-log h</=9.0. Equilibrium measurements were performed as potentiometric titrations complemented by spectrophotometric analysis of a ligand (batch adsorption experiments). The experimental data were evaluated on the basis of the extended constant capacitance model, allowing for inner-sphere and/or outer-sphere complexation. The acid/base properties are described by the equilibria: H(+)+ identical withAlOHleft harpoon ovet right harpoon identical withAlOH(2)(+); log beta(1,1,0(int))=7.46+/-0.04 and identical withAlOH left harpoon ovet right harpoon identical withAlO(-)+H(+); log beta(-1,1,0(int))=-9.87+/-0.12. The specific capacitance was determined as 1.00 F m(-2). The binding of pyrocatechol violet {PCV, 2-[(3,4-dihydroxyphenyl)(3-hydroxy-4-oxocyclohexa-2,5-diene-1-ylidene)methyl]benzenesulfonic acid}, H(4)L, was described by the formation of a single inner-sphere complex according to the reaction identical withAlOH+H(4)Lleft harpoon ovet right harpoon identical withAlL(3-)+3H(+)+H(2)O. Allowing for a charge distribution of this complex between the inner plane and beta-plane (-2, -1), a significant improvement of the fit was obtained. The adsorbed complex exhibited a dark blue color over the pH range 5-8.5, indicative of proton loss from the 1,2-dihydroxyl moiety. Furthermore, DRIFT spectra showed the bonding environment of PCV bound to the surface to exhibit similarities with corresponding catechol adsorption to different aluminium (hydr)oxides. These spectral features turned out to be very similar to soluble catechol complexes of Al(III). Thus, it is suggested that PCV forms a mononuclear chelating complex at the boehmite-water interface. The maximum surface coverage reached was ca. 33%, indicating that the high negative charge of the species may result in surface charge "saturation" rather than saturation of surface binding sites. Steric hindrances caused by the large size of PCV may also contribute to the low surface coverage. Copyright 2000 Academic Press.

Journal Article↗

PubMed1995

Structure-activity relationship of phenolic compounds (phenol, pyrocatechol and hydroquinone) on natural lymphocytotoxicity of carp (Cyprinus carpio).

We have tested the effects of phenol and two diphenols (pyrocatechol and hydroquinone) on a non-specific immune response, i.e. the natural cytotoxic activity, of the carp. After a 12-day exposure of fish, at a concentration of 0.1 mg/l, hydroquinone appeared to exert the most immunotoxic effect in vivo. In vitro, after a preincubation of 1 h, phenol (10(-2) M), pyrocatechol (4.25 x 10(-4) M) and hydroquinone (4.25 x 10(-5) M) decreased the natural cytotoxic activity of lymphoid cell suspension. In vivo and in vitro experiments show that hydroquinone is the most toxic compound, whereas diphenols are more toxic than phenol. These results demonstrate that the study of immune systems can reveal the presence of toxic substances with varying degrees of toxicity. Also, the position of a second hydroxic group on the benzonic nucleus seems to influence the compound toxicity.

Animals↗

PubMed1982

Double-head haptens. Synthesis of and experimentally induced contact sensitivity to substances containing two unrelated haptens, pyrocatechol and alpha-methylene-gamma-butyrolactone, in the same molecule.

A "double-head" hapten containing a pyrocatechol and an alpha-methylene-gamma-butyrolactone moiety (3) and "monofunctional haptens" with either one of these moieties (18 and 19) connected by a six-carbon chain have been synthesized, and their sensitizing capacity was tested on guinea pigs. In the "double-head" hapten, only the pyrocatechol end is "recognized". A possible interpretation of the biological results is offered.

4-Butyrolactone↗

PubMed1999

[Study on the synergistic coloration of tin (II) with pyrocatechol violet and rhodamine B and its application].

In the presence of PVA, a sensitive color reaction of tin (I ) on pyrocatechol violet and rhodamine B has been studied. In a NaAc-HAc (pH = 5.0) medium, tin(II) ions form an ions-associate complex with pyrocatechol violet and rhodamine B. The composition of the complex is Sn (II): PV : RhB = 1 : 2: 4. The maximum absorption of the ions-associate complex is at 560 nm with an apparent molar absorptivity of 1.18 x 10(5) L x mol(-1) x cm(-1). Beer's law is obeyed in the range of 0-15 microg/25 mL of tin. The method is highly selective and has been applied to the determination of trace tin in some objects with satisfactory results.

Benzenesulfonates↗

PubMedDate not supplied

[Inactivation of o-diphenoloxidase in the pyrocatechol oxidation reaction].

The inactivation kinetics of o-diphenoloxidase isolated from potato tubers was studied in the process of pyrocatechol oxidation. The enzyme when saturated with the substrate is inactivated with the inactivation rate constant kin = 0.5-1.0 min-1; kin depends on the initial concentration of pyrocatechol. The ultimate yield of the enzymic reaction product increases linearly with the initial concentration of the enzyme. Introduction of ethylene-diaminosulphate, a substance which condenses with o-quinones, does not increase the operation stability of o-diphenoloxidase. The data obtained evidence for inactivation of o-diphenoloxidase either at the level of the enzyme-substrate complex or due to bimolecular reaction with the substrate.

Catechol Oxidase↗

PubMed2001

Influence of protein composition on total urinary protein determined by pyrocatechol-violet (UPRO vitros) and pyrogallol red dye binding methods.

Influence of protein composition on total urinary protein assays was evaluated for pyrogallol red-molybdate both with and without sodium dodecyl sulfate (SDS) and pyrocatechol violet-molybdate complex (UPRO) techniques. Using mixtures of albumin and gamma-globulins (n = 8; albumin/globulin ratio, 0 to 10), mean recoveries were 79, 77, and 81% for pyrogallol red, pyrogallol red-SDS, and UPRO, respectively. Using diluted myeloma sera (n = 26; A/G ratio, 0.39 to 2.35), mean recovery by the UPRO method was 115% (vs. 63% for pyrogallol red and 83% pyrogallol red-SDS). Results positively correlated with A/G ratio for UPRO (r = 0.69; P < 0.001), pyrogallol red (r = 0.48; P < 0.05), but not pyrogallol red-SDS (r = 0.191; NS). The difference between UPRO and pyrogallol red assays correlated with the A/G ratio (r = 0.82; P < 0.001). In light chain proteinuria (n = 10), no significant difference (< 15%) was observed between techniques, whereas in glomerular selective proteinuria (n = 10), values were significantly higher with the UPRO assay (2.20 +/- 1.61 vs. 1.43 +/- 1.10 g/L; P < 0.02). Our results support the idea that screening for renal diseases can be performed with UPRO or pyrogallol red assays. However, since A/G ratios may vary with renal disease evolution, follow-up of patients with positive proteinuria should be performed using the same assay, preferably the pyrogallol red-SDS.

Bence Jones Protein↗

PubMed1992

Borate and molybdate inhibition of catechol estrogen and pyrocatechol methylation by catechol-O-methyltransferase.

The possibility that boron and molybdenum anions can influence sex steroid metabolism by forming complexes with catechol estrogens has been studied in vitro. The formation of 2-methoxyestrone (2-OHE1 2-Me) from 2-hydroxyestrone (2-OHE1) by catechol-O-methyltransferase (COMT) was followed by measuring the transfer of the radiolabeled methyl group from S-adenosylmethionine. In the presence of both sodium tetraborate and sodium molybdate using a phosphate buffer medium, the formation of 2-OHE1 2-Me decreased as the anion:2-OHE1 molar ratio was increased. However, the reverse effect was observed when using a tris buffer medium and further investigation showed that phosphate and sulphate also enhanced COMT activity in a tris buffer medium. Boric acid affinity medium, used as a substitute for borate salt, also showed a negative relationship with enzyme activity in a phosphate buffer medium, and inhibition of methylation was more marked than with the free anion. Erythrocytes contain appreciable amounts of COMT, which is mostly responsible for the rapid O-methylation of catechol estrogens in blood. The methylation of a simple catechol compound, 1,2-dihydroxybenzene (pyrocatechol) was therefore studied using rat red blood cell lysates. Methylation was inhibited in a concentration-related manner by borate, as found in the studies of 2-OHE1. It is possible that high dietary intakes of boron or molybdenum could regulate the rate of catabolism, or even the metabolic fate of the major estrogens.

Animals↗

PubMed2005

Pyrocatechol violet as a marker to characterize liposomal membrane permeability using the chelation and the first-order derivative spectrophotometry.

Pyrocatechol violet (PV), a chelating agent for cupric ions was used to characterize liposomal membrane permeability. After cupric ions were added to PV liposomes, free PV turned into its chelate (PV-Cu), and encapsulated PV kept stable since liposomal membranes prevented metal ions from permeating. After the light scattering background of liposomes and the absorbance of PV were eliminated by the first-order derivative spectrophotometric method, PV-Cu i.e. free PV in liposome suspensions could be determined without separation. The released PV from liposomes could also be determined. Because PV release is relevant to liposomal membrane permeability, PV becomes a marker to characterize the membrane permeability. This new method was simple, rapid, sensitive, and was used to measure the temperature-dependent liposomal membrane permeability in this paper. Dipalmitoylphosphatidylcholine (DPPC) and soybean lecithin liposomes showed the peaks of release at 40 degrees C and 39 degrees C, respectively.

Benzenesulfonates↗

PubMed2002

Spectrophotometric determination of folic acid in pharmaceutical preparations by coupling reactions with iminodibenzyl or 3-aminophenol or sodium molybdate-pyrocatechol.

Novel coupling reagents are used for the simple and sensitive spectrophotometric determination of folic acid either in pure form or in its pharmaceutical preparations. The methods are based on the probable diazotization of the p-aminobenzoylglutamic acid obtained after reductive clevage of folic acid, followed by either coupling with iminodibenzyl to give a violet product with lambda(max) of 580nm or coupling with 3-aminophenol to produce an orange yellow-colored product with lambda(max) of 460nm. Sodium molybdate and pyrocatechol are used in the third method and the pale red-colored product formed has a lambda(max) of 490nm. The methods are highly reproducible and have been applied to the determination of folic acid in tablets and the results compare favorably with the official method. Common excipients used as additives in pharmaceutical preparations do not interfere in the proposed methods.

Aminophenols↗

PubMed2001

Pyrocatechol violet in pharmaceutical analysis. Part I. A spectrophotometric method for the determination of some beta-lactam antibiotics in pure and in pharmaceutical dosage forms.

A fairly sensitive, simple and rapid spectrophotometric method for the determination of some beta-lactam antibiotics, namely ampicillin (Amp), amoxycillin (Amox), 6-aminopenicillanic acid (6APA), cloxacillin (Clox), dicloxacillin (Diclox) and flucloxacillin sodium (Fluclox) in bulk samples and in pharmaceutical dosage forms is described. The proposed method involves the use of pyrocatechol violet as a chromogenic reagent. These drugs produce a reddish brown coloured ion pair with absorption maximum at 604, 641, 645, 604, 649 and 641 nm for Amp, Amox, 6APA, Clox, Diclox and Flucolx, respectively. The colours produced obey Beer's law and are suitable for the quantitative determination of the named compounds. The optimization of different experimental conditions is described. The molar ratio of the ion pairs was established and a proposal for the reaction pathway is given. The procedure described was applied successfully to determine the examined drugs in dosage forms and the results obtained were comparable to those obtained with the official methods.

Anti-Bacterial Agents↗

PubMed2003

Catalytic effect of supported metal ion complexes on the induced oxidative degradation of pyrocatechol violet by hydrogen peroxide.

Kinetics of the oxidative degradation of pyrocatechol violet dye (PCV) [2-[(3,4-dihydroxyphenyl)(3-hydroxy-4-oxocyclohexa-2,5-dien-1-ylidene) methyl]-benzenesulfonic acid] by H(2)O(2) catalyzed by supported transition metal complexes have been studied. The reaction was followed by conventional UV-vis spectrophotometer at lambda(max)=440 nm in a buffer solution at pH 5.1. The supports used were silica gel and cation exchange resins (Dowex-50W, 2 and 8% DVB), while the complexes were [Cu(amm)(4)](2+), [Cu(en)(2)](2+), [Cu(ma)(4)](2+), [Co(amm)(6)](2+), and [Ni(amm)(6)](2+) (amm=ammonia, en=ethylenediamine, and ma=methylamine). The reaction exhibited first-order kinetics with respect to [PCV] and [H(2)O(2)]. The reactivity of the catalysts is correlated with the redox potential of the metal ions, the type of support, and the amount of supported complexes. The rate of the reaction increases with increasing pH and the addition of NaCl. Addition of SDS and CTAB showed inhibiting effects. The reaction is enthalpy-controlled as confirmed from the isokinetic relationship. A reaction mechanism involved the generation of free radicals as an oxidant has been proposed.

Journal Article↗

PubMed1987

Double-headed haptens with pyrocatechol (poison ivy like) and methylene lactone functional groups: a search for skin-tolerance inducers.

In order to develop new theories for desensitization, a potential skin sensitizer, 1, with two different haptenic ends, a pyrocatechol group and an alpha-methylene-gamma-butyrolactone moiety, separated by a straight nine-carbon-atom chain has been prepared and used to sensitize guinea pigs. A "monohapten" 8 containing an electrophylic alpha-methylene-gamma-butyrolactone, connected to a dimethoxybenzene group, has also been prepared. Both the "bihapten" 1 and the "monohapten" 8 were shown to be sensitizers. Bihapten 1 sensitized animals recognized only bihapten 1 (and not the lactone 8) while monohapten 8 sensitized guinea pigs reacted to both 8 and 1. Bihapten 1 treated animals were further sensitized to monohapten 8 and challenged to the latter: the skin intensity reaction was significantly lower than the test to 8 in 8-sensitized animals. Bihapten 1 seems therefore to "tolerize" against the alpha-methylene-gamma-butyrolactone end.

Animals↗

PubMed2001

Speciation of aluminium(III) in natural waters using differential pulse voltammetry with a pyrocatechol violet-modified electrode.

A differential pulse voltammetric (DPV) procedure is proposed for the speciation of aluminium in natural waters using Pyrocatechol Violet chemically modified electrodes (PCV-CMEs). This novel speciation idea is based on the selective determination of different AlIII forms under two pH conditions. The labile monomeric Al fraction (mainly inorganic Al) is analysed at pH 4.8 (0.20 mol dm(-3) NaOAc-HOAc) and the total monomeric Al fraction is analysed at pH 8.5 (0.20 mol dm(-3) NH3.H2O-NH4Cl). The difference is thought to be caused by the weak competition ability of PCV to sequester AlIII from AlIII-natural organic matter complexes. This sensitive and simple speciation method has been applied successfully to aluminium speciation in natural waters sampled from different regions of China. Five fractions are measured directly or indirectly: (i) labile monomeric Al; (ii) total monomeric Al; (iii) acid reactive Al; (iv) non-labile monomeric Al; and (v) acid soluble Al. The results are in satisfactory agreement with those obtained by Driscoll's 8-hydroxyquinoline extraction-ion exchange method.

Aluminum↗