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PubMed1997

Protective effects of hydroxybenzoic acids and their esters on cell damage induced by hydroxyl radicals and hydrogen peroxides.

The purpose of this study was to evaluate the hydroxyl radical scavenging activities of hydroxybenzoic acids and their esters from both chemical and biological aspects. These activities of hydroxybenzoic acids and their related compounds were estimated by ESR-spin trapping method, in which 3,4,5-trihydroxybenzoic acid and its ethyl and propyl esters showed the highest activities as estimated by IC50 value (50% inhibition concentration of hydroxyl radicals generated in the system): 78.04 +/- 11.23, 95.95 +/- 2.64, and 86.46 +/- 2.31 microM, respectively. In addition, 3,4,5-trihydroxybenzoic acid (gallic acid) at a concentration of 25 microM, protected against dermal fibroblast cell damage induced by H2O2, and enhanced the survival to 83.8 +/- 3.1%, in which the survival of control was 44.2 +/- 1.0%. Based on these results, the pretreatment effects of 3,4,5-trihydroxybenzoic acid n-alkyl esters on cell damage induced by H2O2 were examined. The survival of fibroblasts pretreated with the esters increased depending on the alkyl chain-length. Both C12 and C16 alkyl esters gave almost complete cell survival of 89.5 +/- 2.0% and 91.3 +/- 1.0%, respectively. The order of the protective effects of the compounds was in good agreement with that of their partition coefficients, suggesting that 3,4,5-trihydroxybenzoic acid alkyl esters are incorporated into fibroblasts, and thus prevent the cells from the toxicity caused by H2O2. In addition, an increase of intracellular peroxide formation in fibroblasts induced by UVA-irradiation, was suppressed to 2.27 +/- 0.41 nmol/10(4) cells by pretreatment with C16 alkyl ester at a concentration of 25 microM. Since 3,4,5-trihydroxybenzoic group has been demonstrated to possess a potent scavenging activity of hydroxyl radicals, this moiety was indicated to be important in preventing cell damage induced by UVA or H2O2: in turn, these produce hydroxyl radicals in the presence of trace metal ions such as iron and copper in cells.

Cell Survival↗
PubMed2005

Constitutive synthesis of enzymes involved in 2-aminophenol metabolism and inducible synthesis of enzymes involved in benzoate, p-hydroxybenzoate, and protocatechuate metabolism in Pseudomonas sp. strain AP-3.

Pseudomonas sp. strain AP-3 grows on benzoate, p-hydroxybenzoate, protocatechuate, and 2-aminophenol as sole carbon and energy source. This strain converted benzoate and p-hydroxybenzoate to catechol and protocatechuate respectively, which were metabolized via the ortho-cleavage pathway. The enzymes responsible for these reactions were shown to be inducible. In contrast, strain AP-3 constitutively expresses the enzymes involved in the metabolism of 2-aminophenol.

Aminophenols↗
PubMed2000

3-Hydroxybenzoate:coenzyme A ligase from cell cultures of Centaurium erythraea: isolation and characterization.

In xanthone biosynthesis, 3-hydroxybenzoate:coenzyme A ligase (3HBL) supplies the starter substrate for the formation of an intermediate benzophenone. 3HBL from cell cultures of the medicinal plant Centaurium erythraea was purified to apparent homogeneity using a seven-step-procedure. The enzyme was an AMP-forming CoA ligase with a Km = 14.7 microM for 3-hydroxybenzoic acid, 8.5 microM for coenzyme A and 229 microM for ATP. The pH and temperature optima were 7.5 and 35 degrees C, respectively. In SDS-PAGE, two polypeptides of Mr 41,500 and 40,500 were detected. Both proteins were structurally related to each other as shown by tryptic digestion. Their N-termini were blocked. The difference in their apparent molecular masses could not be attributed to glycosylation. 3HBL had a native Mr of approx. 50,000 and is thus active as a monomer.

Adenosine Monophosphate↗
PubMedDate not supplied

Formation of benzoic acid and p-hydroxybenzoic acid in the blue green alga Anacystis nidulans: a thylakoid-bound enzyme complex analogous to the chloroplast system.

The photosynthetic procaryote Anacystis nidulans converts L-phenylalanine and L-tyrosine into benzoic acid and p-hydroxybenzoic acid, respectively. Results obtained with thylakoid fractions support the hypothesis that the reaction sequence is catalyzed by thylakoid-bound enzyme complexes consisting of phenylalanine ammonia-lyase and benzoate synthase of tyrosine ammonia-lyase and p-hydroxybenzoate synthase, respectively. Btoh complexes do not accept phenylacetic acids as substrates, and cinnamic acids only at a small extent. These properties suggest a striking similarity to a benzoic acid-synthesizing enzyme system from higher plants which is situated at the thylakoid membrane of chloroplasts. The respective complexes of Dunaliella marina and Porphyridium sp. were included in this comparison.

Benzoates↗
PubMedDate not supplied

Determination of p-hydroxybenzoic acid esters in cosmetics by liquid chromatography with ultraviolet and fluorescence detection.

A simple, precise, and accurate liquid chromatographic method with both ultraviolet (UV) and fluorescence detection is described for the determination of methyl, ethyl, propyl, and butyl p-hydroxybenzoates (PHBA-esters) in cosmetics. sec-Butyl p-hydroxybenzoate is added to the sample as an internal standard. Then the PHBA-esters are extracted with ether, the ether is evaporated to dryness, and the residue is dissolved in 60% (v/v) acetonitrile. The acetonitrile solution is passed through a Sep-Pak C18 cartridge to remove co-extracted lipids. PHBA-esters are determined by reverse-phase liquid chromatography with UV detection at 254 nm and fluorescence detection at ex 280 nm, em 305 nm. The mobile phase is acetonitrile-water (35 + 65). The method was linear over the concentration range of 0.005-0.15 mg/mL. Mean recoveries of each PHBA-ester were 98.9-102.7% (coefficients of variation less than or equal to 2.0%).

Chromatography, Liquid↗
PubMedDate not supplied

[Preparatory metabolism of p-hydroxybenzoic acid in Candida tropicalis].

A technique of experimental adaptation was used to obtain mutants of Candida tropicalis which were able to utilize p-hydroxybenzoic acid as the sole source of carbon and energy. The preparatory metabolism of p-hydroxybenzoic acid involves the following stages: PHBA leads to quinol leads to hydroxyquinol leads to maleylacetic acid leads to beta-ketoadipic acid. The enzyme system which catalyzes oxidative decarboxylation of PHBA mediates also oxidative decarboxylation of protocatechuic, beta-resorcylic and gallic acids, i.e. compounds having a hydroxyl group in para position with respect to the carboxyl of hydroxyl derivatives of benzoic acid. Benzoic, salicyclic and gentisic acids are not substrates of this enzyme system. A technique is proposed for rapid indentification of beta-ketoadipic acid by thin-layer chromatography. The authors believe that methods used to study preparatory metabolism, on the basis of the Stanier theory of "simultaneous adaptation", are not quite reliable and may lead to erroneous conclusions.

Candida↗
PubMed1980

Primary and tertiary structure studies of p-hydroxybenzoate hydroxylase from Pseudomonas fluorescens. Isolation and alignment of the CNBr peptides; interactions of the protein with flavin adenine dinucleotide.

p-Hydroxybenzoate hydroxylase from Pseudomonas fluorescens contains six methionine residues, one of which is N-terminal. After CNBr cleavage five peptides, ranging from 13 to 158 residues in length, and free homoserine were isolated and purified by repeated gel filtration. The alignment of the CNBr fragments was deduced from a 0.25-nm electron density map and sequence data. The isolated fragments account for the entire polypeptide chain. The amino acid sequence of the N-terminal quarter of the polypeptide chain was determined. The X-ray results together with the sequence data yielded details of the binding of FAD. The AMP moiety was bound to a beta alpha beta unit resembling that found in the dehydrogenases. Hydrogen bonds were present between the protein and the ribityl residue and the isoalloxazine ring. Furthermore, a homology was found between the N-terminal amino acid sequence of p-hydroxybenzoate hydroxylase and another enzyme containing FAD, viz. D-amino acid oxidase. This finding suggests the presence of a mononucleotide binding fold at the N terminus of the latter.

4-Hydroxybenzoate-3-Monooxygenase↗
PubMed1982

A histidine residue in p-hydroxybenzoate hydroxylase essential for binding of reduced nicotinamide adenine dinucleotide phosphate.

Chemical modification with diethylpyrocarbonate (ethoxyformic anhydride) was examined to demonstrate the existence of an essential histidine residue at the NADPH-binding site of p-hydroxybenzoate hydroxylase (EC 1.14.13.2) from Pseudomonas desmolytica. Among some ligands, NADPH was noticeable in protecting the enzyme from the modification-caused inactivation. Although several amino acid residues were modified during the inactivation process, inhibition of the enzyme could be correlated with modification of a single histidine residue which was masked by addition of NADPH. The pK of the essential histidine residue was estimated to be 6.5-6.7. The Kd (Km) for NADPH of the inactivated enzyme was shown to have been increased greatly, although the Kd for substrate (p-hydroxybenzoate) was not changed.

4-Hydroxybenzoate-3-Monooxygenase↗
PubMedDate not supplied

[Activation of 14C-n-hydroxybenzoate and 2-14C-mevalonate incorporation into ubiquinone in regenerating rat liver].

Incorporation of 14C-p-hydroxybenzoate and 2-14C-mevalonate into ubiquinone in vivo and in vitro was distinctly increased in regenerating rat liver lobes within 1st and 2nd day after partial hepatectomy, whereas incorporation of 2-14C-mevalonate into sterols was unaltered. The stimulation observed was partially due to an increase in the rate of biosynthesis of the enzymes, catalysing the incorporation of the label into the ubiquinone. Preliminary administration of cholesterol or cholesterol with bile into rats caused an inhibition of the multistep biosynthesis of sterols at several sites and stimulated the ubiquinone synthesis. Intravenous administration of ubiquinone-9 emulsion was accompanied by more than 3-fold increase in concentration of the substance in regenerating liver tissue and did not cause any effect on the rate of incorporation of 14C-p-hydroxybenzoate and 14-C-methyl methionine into slices, obtained from this tissue.

Animals↗
PubMed1976

Flavin-oxygen derivatives involved in hydroxylation by p-hydroxybenzoate hydroxylase.

Para-hydroxybenzoate hydroxylase (EC 1.14.13.2) from Pseudomonas fluorescens is one of a group of flavoproteins which insert molecular oxygen into aromatic rings to form phenols. To determine the mechanism of oxygen insertion by this enzyme, an extensive study was made of the reaction with O2 of reduced enzyme in complex with various aromatic molecules. Reactions were studied by following absorbance changes with time with a stopped-flow spectrophotometer. Analysis of multiphasic reactions led to the detection of a minimum of three transient intermediates with characteristic absorption spectra involved in the process of hydroxylation. The initial interaction of oxygen with the reduced enzyme characteristically produces a derivative of FAD (maximum absorbance 380 to 390 nm) which is probably C(4a) peroxyflavin. Depending on the aromatic compound bound to the enzyme, this intermediate decays either to oxidized, enzyme-bound flavin and H2O2 or transfers an atom of oxygen to the aromatic compound. The process of oxygen transfer forms a derivative of FAD of unknown structure (maximum absorbance 390 to 420 nm), which subsequently decays to the third intermediate observed (maximum absorbance 380 to 385 nm), which is probably C(4a) hydroxyflavin. The decay of this last intermediate results in the formation of oxidized enzyme, and the liberation of hydroxylated product and H2O. In an extension of substrate specificity studies it was found that p-aminobenzoate is a substrate and 5-hydroxypicolinate is an effector for p-hydroxybenzoate hydroxylase. The binding of aromatic compounds to the reduced enzyme was observed by following shifts in the absorption spectrum of enzyme bound FADH2, permitting the determination of dissociation constants and kinetics of binding.

4-Hydroxybenzoate-3-Monooxygenase↗
PubMed1998

Key enzymes for the degradation of benzoate, m- and p-hydroxybenzoate by some members of the order Actinomycetales.

A preliminary screening of numerous species of the order Actinomycetales, especially of the genera Mycobacterium, Nocardia, Rhodococcus, Pseudonocardia, and Streptomyces, showed that many of them are able to metabolize benzoate (B) and p-hydroxybenzoate (pHB) as indicated by growth and change of color of the pH-indicator of an agar medium. Subsequent experiments with liquid cultures which allowed the analysis of substrate utilization by thin layer chromatography confirmed these results. The study of the degradative pathway proved that B was metabolized via catechol (C), pHB via protocatechuate (P) and m-hydroxybenzoate (mHB) via gentisate (G). The aromatic ring of C and P was subjected to an ortho-cleavage; only one strain of Noc. asteroides degraded C via a meta-cleavage, but P via an ortho-cleavage. Cell free extracts of four selected organisms exhibited activity of C-1,2-dioxygenase (C-1,2-O) and/or P-3,4-dioxygenase (P-3,4-O), depending on the growth substrate used for precultivation. In Streptomyces C-1,2-O was only found in cells grown on B, and P-3,4-O only in cells grown on pHB. On the contrary, in Rhodococcus rhodochrous B-cells oxidized C as well as P, while P-cells possessed only P-3,4-O-activity.

Actinomycetales↗
PubMed1999

Main and interaction effects of acetic acid, furfural, and p-hydroxybenzoic acid on growth and ethanol productivity of yeasts.

The influence of the factors acetic acid, furfural, and p-hydroxybenzoic acid on the ethanol yield (YEtOH) of Saccharomyces cerevisiae, bakers' yeast, S. cerevisiae ATCC 96581, and Candida shehatae NJ 23 was investigated using a 2(3)-full factorial design with 3 centrepoints. The results indicated that acetic acid inhibited the fermentation by C. shehatae NJ 23 markedly more than by bakers' yeast, whereas no significant difference in tolerance towards the compounds was detected between the S. cerevisiae strains. Furfural (2 g L-1) and the lignin derived compound p-hydroxybenzoic acid (2 g L-1) did not affect any of the yeasts at the cell mass concentration used. The results indicated that the linear model was not adequate to describe the experimental data (the p-values of curvatures were 0.048 for NJ 23 and 0.091 for bakers' yeast). Based on the results from the 2(3)-full factorial experiment, an extended experiment was designed based on a central composite design to investigate the influence of the factors on the specific growth rate (mu), biomass yield (Yx), volumetric ethanol productivity (QEtOH), and YEtOH. Bakers' yeast was chosen in the extended experiment due to its better tolerance towards acetic acid, which makes it a more interesting organism for use in industrial fermentations of lignocellulosic hydrolysates. The inoculum size was reduced in the extended experiment to reduce any increase in inhibitor tolerance that might be due to a large cell inoculum. By dividing the experiment in blocks containing fermentations performed with the same inoculum preparation on the same day, much of the anticipated systematic variation between the experiments was separated from the experimental error. The results of the fitted model can be summarised as follows: mu was decreased by furfural (0-3 g L-1). Furfural and acetic acid (0-10 g L-1) also interacted negatively on mu. Furfural concentrations up to 2 g L-1 stimulated Yx in the absence of acetic acid whereas higher concentrations decreased Yx. The two compounds interacted negatively on Yx and YEtOH. Acetic acid concentrations up to 9 g L-1 stimulated QEtOH, whereas furfural (0-3 g L-1) decreased QEtOH. Acetic acid in concentrations up to 10 g L-1 stimulated YEtOH in the absence of furfural, and furfural (0-2 g L-1) slightly increased YEtOH in the absence of acetic acid whereas higher concentrations caused inhibition. Acetic acid and furfural interacted negatively on YEtOH.

Acetic Acid↗
PubMed1979

The metabolic activation of benzo(a)pyrene and 9-hydroxybenzo(a)pyrene by liver microsomal fractions.

A rat liver microsome-mediated bacterial mutagenicity test showed 9-hyroxybenzo(a)pyrene to be significantly more effective as a pre-mutagen than benzo(a)pyrene. Experiments measuring the ability of these compounds to be metabolically activated to moieties that alkylate exogenous DNA demonstrated that 9-hydroxybenzo(a)pyrene was almost six times more effective than benzo(a)pyrene itself. Addition of trichloropropene-2,3-oxide to the reaction mixture enhanced the mutagenicity and DNA alkylation by benzo(a)pyrene but had little or no effect on the 9-hydroxybenzo(a)pyrene-mediated mutagenicity and alkylation. On the other hand, 7,8-benzoflavone inhibited the microsome-mediated mutagenicity and DNA alkylating activity of both hydrocarbons.

Alkylation↗
PubMed1995

Transesterification reactions of parabens (alkyl 4-hydroxybenzoates) with polyols in aqueous solution.

Accelerated stability tests of aqueous solutions containing parabens and polyols were performed using concentrations similar to pharmaceutical and cosmetic formulations. Reaction products were detected in these solutions by HPLC and identified by chromatographic and spectroscopic means. Using xylitol and methylparaben as model reactants, three unknown peaks having the relation 1:2:4 were obtained together with the hydrolysis product 4-hydroxybenzoic acid. Diode array detection gave identical UV spectra for each peak with a maximum at 255 nm. The structures of the isomeric 1-, 2-, and 3-xylityl 4-hydroxybenzoic acid esters were proved by means of LC-MS, GC-MS, and NMR and correlated to the peaks in the HPLC chromatograms. The rate of the transesterification was shown to be highest in strongly alkaline medium (ph 10-11), whereas equilibration of the reaction was optimally balanced at pH 8-9. An increase of polyol concentration enhanced the formation of the esters. The reactivity of different substituted parabens was higher in the case of parabens with a short alkyl ester function. Similar reaction profiles were observed with C3-C6 polyols, but no transesterification took place when aldoses were used.

Chromatography, High Pressure Liquid↗
PubMed1995

Microbial production of specifically ring-13C-labelled 4-hydroxybenzoic acid.

When transformed with a recombinant vector carrying the ubiC gene (encoding chorismate pyruvate-lyase, EC 4.1.3.27) the triple mutant (Phe-, Trp-, Tyr-) Klebsiella pneumoniae 62-1 excretes 4-hydroxybenzoic acid instead of chorismic acid. The recombinant strain can be used to produce in high yield specifically ring-labelled 4-hydroxybenzoic acid from isotopically labelled glucose.

Anthranilate Synthase↗
PubMed1975

Aromatic metabolism in the fungi. Growth of Rhodotorula mucilaginosa in p-hydroxybenzoate-limited chemostats and the effects of growth rate on the synthesis of enzymes of the 3-oxoadipate pathway.

Rhodotorula mucilaginosa was grown in p-hydroxybenzoate-limited chemostats over the dilution rate (D) range 0.01 to 0.17 h-1 and growth was adequately described by the Monod theory when maintenance energy requirements were considered. The p-hydroxy-benzoate affinity constant, K8, had the relatively high value of 270 mg/I. The yield from p-hydroxbenzoate varied with dilution rate but was constant above D equal 0.07 h-1 at 0.56 g yeast/g substrate utilised. The maintenance coefficeint for growth on the aromatic substrate was 20 mg/g yeast/hr. Culture viability decreased linearly as the dilution rate was reduced. 4-Hydroxybenzoate 3-mono-oxygenase, protocatechuate 3,4-dioxygenases, 3-carboxymuconate cyclase and 3-carboxymuconolactone hydrolase activities were dilution rate-dependent, results which accord with the substrate in inducibility of these enzymes. Under carbon-limited growth conditions the addition of glucose, a catabolite repressor of these enzymes, to the aromatic medium stimulated their synthesis. Data were also obtained which indicated that whereas the synthesis of the cyclase and the hydrolase was coordinately controlled, that of the first two enzymes of the 3-oxodipate pathway was under independent control.

Benzoates↗
PubMed2006

Automated determination of the pKa values of 4-hydroxybenzoic acid in cosolvent-water mixtures and related solvent effects using a modified HPLC system.

An automated spectrophotometric method based on an HPLC system with a diode array detector was used to determine the pK(a) values of compounds with low water solubility in a universal buffer containing acetonitrile as cosolvent. The column of the system was replaced with a capillary connecting the injection system and the diode array detector. Specific solvent effects were corrected for using the dielectric constants of the mixed solvent and pure water. The method was tested using 4-hydroxybenzoic acid and the results were compared with those obtained with a spectrophotometer. Linear regression lines with different slopes were obtained from spectrophotometric measurements of different cosolvent-water mixtures. These effects were shown to depend upon the polarity of the solvent-water mixture, and they were explained by the solvatochromic behavior of the 4-hydroxybenzoic acid in the solvent-water mixture.

Chromatography, High Pressure Liquid↗
PubMed2000

Occupational exposure to polycyclic aromatic hydrocarbons in a fireproof stone producing plant: biological monitoring of 1-hydroxypyrene, 1-, 2-, 3- and 4-hydroxyphenanthrene, 3-hydroxybenz(a)anthracene and 3-hydroxybenzo(a)pyrene.

OBJECTIVES: Assessment of external and internal exposure to polycyclic aromatic hydrocarbons (PAH) in a fireproof stone producing plant. METHODS: Five personal and four stationary air measurements were performed to determine the concentrations of benz(a)anthracene, benzo(a)pyrene, benzo(b)fluoranthene, chrysene, dibenz(a,h)anthracene, fluoranthene, phenanthrene and pyrene, in air. To estimate internal exposure, we determined the urinary excretion of 1-hydroxypyrene, 1-, 2-, 3-, and 4-hydroxyphenanthrene, 3-hydroxybenz(a)anthracene and 3-hydroxybenzo(a)pyrene in 19 workers, using a sensitive and reliable high-performance liquid chromatographic method with fluorescence detection. RESULTS: During the production of fireproof stones, the German technical exposure limit (TRK) for benzo(a)pyrene of 2 microg/m3 was exceeded in two cases. The mean values of the sum of eight PAHs were 12.6 microg/m3 (stationary air measurement) and 22.2 microg/m3 (personal air measurement). Urinary 1-hydroxypyrene excretion predominated, with a median of 11.1 microg/g creatinine (creat.), followed by 3-hydroxyphenanthrene (median 2.2 microg/g creat.), 1-hydroxyphenanthrene (median 1.9 microg/g creat.) and 2-hydroxyphenanthrene (median 1.6 microg/g creat.). 4-Hydroxyphenanthrene (median 0.3 microg/g creat.) and 3-hydroxybenz(a)anthracene (median 0.17 microg/g creat.) were found in far lower concentrations, while 3-hydroxybenzo(a)pyrene was found only in very low concentrations (median 0.014 microg/g creat.). No correlations could be detected for a relationship between external and internal exposure. A significant correlation between urinary metabolite concentrations could be calculated only for 3-hydroxybenz(a)anthracene and 1-hydroxypyrene. CONCLUSIONS: In comparison with other industries, the internal PAH exposure at workplaces in a fireproof stone producing plant is high. This is probably caused by dermal PAH-absorption. Therefore, biological monitoring must be performed in the health surveillance of fireproof stone producing workers. The urinary PAH metabolites should be determined: 3-hydroxybenz(a)anthracene could probably be used as a biomarker representing the group of carcinogenic PAH.

Adult↗