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PubMed1995

[Synthesis and properties of membrane-addressed antioxidants based on phosphorylated pyrocatechols].

Amphiphilic membrane-addressed antioxidants differing in their hydrophobic-hydrophilic balance, 3,5-di-tert-butyl-2-hydroxyphenyl phosphate, (3,5-di-tert-butyl-2-hydroxyphenyl)hexadecyl phosphate, and (3,5-di-tert-butyl-2-hydroxyphenyl)-5-cholesten-3 beta-yl phosphate, were synthesized starting from 3,5-di-tert-butyl-o-quinone. Even at 10(-8) M concentration, 3,5-di-tert-butyl-2-hydroxyphenyl phosphate and (3,5-di-tert-butyl-2-hydroxyphenyl)hexadecyl phosphate inhibit formation of malonic aldehyde during peroxidation of lipids from rat brain homogenate initiated with a Fe(2+)-ascorbate system. At 10(-4) M and higher concentrations of antioxidants in the brain homogenate, the formation of malonic aldehyde is inhibited more efficiently than with tocopherol at the same concentrations.

Animals↗
PubMed1976

[Determination of tin in food products using pyrocatechol violet].

Some incorrect points are referred to of Part II of Bulgarian State Standard 6853-74 "Canned fruits, vegetables, meat, and meat-and-vegetables. Determining the content of stannum with the use of pyrocatecholviolet" rendering difficult the analytic process and leading to false results. Another method for the evaluation of the stannum content making use of pyrocatecholviolet has been applied instead as suggested by the International Federation of Chemists. It makes feasible the determination of even small amounts of stannum (0-30 mug) which are usually encountered in the food products. A mathematic and statistical processing of the results obtained has been made.

Bulgaria↗
PubMed2005

Inter- and intramolecular hydrogen bonding in phenol derivatives: a model system for poly-L-tyrosine.

The ultrafast dynamics of solutions of phenol and two phenol derivatives--hydroquinone (1,4-benzenediol) and pyrocatechol (1,2-benzenediol)--have been studied with Optically Heterodyne-Detected Optical Kerr-Effect (OHD-OKE) spectroscopy. The solvents, methanol and acetonitrile, were selected to provide strong and weak solvent-solute hydrogen-bonding interactions, respectively, while pyrocatechol features an intramolecular hydrogen bond. Together these provide a series of model systems for polypeptides such as polytyrosine, which facilitate the direct study of inter- and intramolecular hydrogen bonding. A broad contribution to the Raman spectral density of the methanol solutions at frequencies between 150 and 300 cm(-1) has been observed that is absent in acetonitrile. This contribution has been assigned to solvent-solute hydrogen-bond stretching vibrations. The OHD-OKE response of poly-L-tyrosine has been measured and was found to contain a similar contribution. Density functional theory geometry optimizations and normal mode calculations have been performed using the B3LYP hybrid functional and 6-311++G** basis set. These have yielded a complete assignment of the low-frequency Raman and far-infrared spectra of pyrocatechol for the first time, which has provided information on the nature of the intramolecular hydrogen bond of pyrocatechol.

Computer Simulation↗
PubMedDate not supplied

[Stability and catalytic properties of o-diphenol oxidase. 1. Oxidation of o-diphenols].

o-Diphenoloxidase from potato tubers is inactivated in the course of the oxidation reaction of o-diphenols at the level of the enzyme-substrate complex. At 25 degrees C of the reaction mixture the enzyme inactivation rate constants (Kin) in oxidation of 10 mM solutions of the substrates were: for pyrocatechol--0.48 min-1; 3,4-dihydroxyphenylethylamine (DOP-amine)--0.52 min-1; 3,4-dihydroxyphenylalanine (DOPA)--0.17 min-1; noradrenaline--0.12 min-1; 3,4-dihydroxybenzaldehyde (DHBA)--0.032 min-1; 3,4-dihydroxybenzoic acid (DHBAc)--0.01 min-1; gallic acid--0.01 min-1. Kin of the enzyme in oxidation of pyrocatechol does not depend practically on pH, ionic strength and polarity of the medium, but rises with its temperature. For a temperature range from 20 to 40 degrees C the effective activation energy calculated in terms of the Arrhenius equation is equal to 28 kJ/mol and the preexponential value for the given preparation was 38 850 min-1. The enzyme activity is determined by the substituent nature in the substrate molecule: electron-donor groups (--CH2--) accelerate the oxidation as compared to nonsubstituted pyrocatechol and electron-acceptor groups (--COOH, --CHO) make it more difficult. If the o-diphenoloxidase activity in oxidation of a 10 mM solution of pyrocatechol is 100%, then the oxidation rate of DOP-amine taken in the same concentration would be 111, DOPA--61, noradrenaline--24, DOBA--2,7, DHBA--0.7, gallic acid--0.8%.(ABSTRACT TRUNCATED AT 250 WORDS)

Catalysis↗
PubMedDate not supplied

[Enzymatic synthesis of 3,4-dihydroxyphenyl-L-alanine by free and immobilized Citrobacter freundii cells].

The Citrobacter freundii 62 cells immobilized in PAAG and possessing the tyrosine-phenol-lyase (TPL) activity catalyse the synthesis of 3,4-dihydroxyphenyl-L-alanine (DOPA) from pyrocatechol and ammonium pyruvate. The synthesis of DOPA was studied using both free and immobilized bacterial cells. When the concentration of pyrocatechol is over 0.1 M the TPL activity of the cells is inhibited. The concentration of pyrocatechol can be increased up to 0.3 M by using an equimolar mixture of pyrocatechol and boric acid. The addition of ascorbic acid as an antioxidant results in a lower TPL activity of both free and immobilized bacterial cells.

Acrylic Resins↗
PubMed1998

[Antimicrobial and membranolytic activity of sterically hindered phenols].

Antimicrobial activity of some complicated space phenols (screened) was studied. The compounds had different activities against grampositive bacteria and were inactive against gramnegative microbes. Di-tertiary butyl derivatives of pyrocatechol and resorcin showed the highest activities. The MICs of such derivatives for the collection strains of Bacillus megaterium, Bacillus subtilis and Staphylococcus aureus were 8 to 30 micrograms/ml and exceeded 6-25 times those of the nonsubstituted analogs. The derivatives of pyrocatechol and resorcin impaired the membrane permeability in susceptible intact cells of B.megaterium and S.aureus 209P and had no effect on the membrane permeability of the Escherichia coli resistant cells. In concentrations up to 200 micrograms/ml the nonsubstituted analogs of pyrocatechol and resorcin did not impair the membrane permeability in the intact cells of the above bacteria. Di-tertiary butyl derivatives of pyrocatechol and resorcin had lytic activity with respect to cytoplasmic membranes (protoplasts) of B.megaterium and had no lytic action on E.coli spheroplasts. The antimicrobial spectrum correlated with the membranotropic properties of the compounds. It was suggested that the target of the antimicrobial action of the screened phenols was the bacterial cell cytoplasmic membrane.

Anti-Bacterial Agents↗
PubMed1991

Inhibitory effects of catechol derivatives on arachidonic acid-induced aggregation of rabbit platelets.

Pyrocatechol and other non-substituted dihydric phenols, which have strong redox power, inhibited arachidonic acid-induced aggregation of rabbit platelets at much lower concentrations than those at which these phenols inhibited stable prostaglandin endoperoxide, U46619-induced aggregation. Among non-substituted dihydric phenols, pyrocatechol was most potent. In order to clarify the physicochemical properties of the phenolic compounds which control the inhibitory potencies of dihydric phenols, we observed the inhibitory effects of 3- and 4-substituents of pyrocatechol on arachidonic acid-induced platelet aggregation. Among seven derivatives tested, the inhibitory effect of 4-C6H5-substituent was strongest and 4-COOH-substituent was weakest. Inhibitory effects of the catechol derivatives were well correlated with the quotients of their hydrophobicities and oxidation-reduction potentials. Inhibitory effects of hydroquinone and resorcinol were also on the same correlation line. These results suggest that the inhibitory effects of catechol derivatives and other dihydric phenols are controlled by two physicochemical properties: oxidation-reduction potential and hydrophobicity.

Animals↗
PubMed1976

Effect of catechol-thiol conjugates on tyrosinase-dependent tyrosine hydroxylation.

1. The tyrosinase reaction in the presence of a thiol compound was studied using mushroom tyrosinase (EC 1.10.3.1) with regard to catechol-thiol conjugates. 2. Although tyrosine hydroxylation of tyrosinase was extremely decreased in the presence of a thiol compound, the inhibitory effect was removed by the addition of a pyrocatechol-cysteine conjugate, S-(2,3-dihydroxyphenyl) cysteine, which was not oxidized by the enzyme. 3. The pyrocatechol-cysteine conjugate was also able to shorten the lag period of tyrosinase-dependent tyrosine hydroxylation. 4. The sigmoidal reaction curve of tyrosine hydroxylation observed in the presence of sulfhydryl compounds was found to be caused by the catechol-thiol conjugates, the final products of the enzyme reaction, which counteract the inhibitory effect of sulfhydryl compounds. 5. The pyrocatechol-cysteine conjugate, on the other hand, was shown to cause the decrease of the reaction rate of the enzyme during incubation.

Basidiomycota↗
PubMedDate not supplied

[Regulation of terephthalate catabolism in Rhodococcus rubropertinctus].

The regulation of terephthalate catabolism was studied in Rhodococcus rubropertinctus which decomposed this synthetic monomer. The pathway (a) of terephthalate (TP) catabolism is as follows: TP----benzoate----4-hydroxybenzoate----protocatechuate----pyrocatechol-- --cycle ortho-cleavage. The following results were obtained when studying why two other catabolic pathways were realized if benzoate and 4-hydroxybenzoate were taken as a sole carbon source, namely, (b) benzoate----pyrocatechol----cycle cleavage and (c) 4-hydroxybenzoate----protocatechuate----cycle cleavage. TP seemed to cause the divergence of pathways (a) and (b) by repressing the system of benzoate oxidation to pyrocatechol. In pathway (c), benzoate repressed the synthesis of enzymes which catalysed protocatechuate oxidation. Pathway (b) was switched over to (a) when the strain was grown in a medium containing TP and benzoate at a benzoate concentration above 5 mM. Here, the concentration of benzoate (first exogenous and later formed from TP) played a key role. R. rubropertinctus growth in a medium with TP and glucose had diauxic characteristics.

Biodegradation, Environmental↗