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PubMed2003

[Determination of six p-hydroxybenzoic acid esters in laver (nori) by HPLC].

A rapid and simple method was developed for simultaneous determination of methyl, ethyl, isopropyl, npropyl, isobuthyl and n-buthyl p-hydroxybenzoic acid esters (PHBA-Es) in laver by HPLC. Six PHBA-Es were extracted from laver with n-hexane-ethyl acetate (1:1) by shaking. The extract was evaporated. The residue was dissolved in methyl alcohol and determined by HPLC. Recoveries of six PHBA-Es spiked in laver were 93.6-101.2% at the level of 2 micrograms/g.

Chromatography, High Pressure Liquid↗
PubMed2006

Effect of denaturants on the structure and activity of 3-hydroxybenzoate-6-hydroxylase.

The effect of denaturants such as urea, sodium dodecylsulphate (SDS), guanidinium hydrochloride (Gu.HCl) on the structure of enzyme 3-hydroxybenzoate-6-hydroxylase was studied using intrinsic fluorescence and far and near-UV-CD spectroscopic techniques. Also, activity profiles of the enzyme, as a function of increasing concentrations of denaturants were studied. The far-UV CD spectrum of the enzyme did not show appreciable alterations in the presence of urea, SDS or Gu.HCl, thereby suggesting that the protein does not undergo gross conformational changes in its alpha-helical secondary structure. The treatment of enzyme with 2 M urea resulted in almost complete loss of catalytic activity, accompanied by the reduction of emission fluorescence of enzyme. Similarly, treatment with 0.01% SDS also caused almost complete loss of activity and quenching of enzyme fluorescence as well as a red shift in the emission peak. In addition, reduction in the intensity of near-UV-CD spectrum, especially at 280 nm was observed. About 70% of the activity was lost by treatment with 20 mM Gu.HCl, accompanied by quenching of intrinsic fluorescence of the enzyme. The change in intrinsic fluorescence of the enzyme in the presence of 5 mM-100 mM Gu.HCI could be correlated to progressive loss of catalytic activity. Thus, intrinsic fluorescence (due to tryptophan residues) could be used as an effective probe to provide an insight into the relation between the activity and subtle conformational changes of the enzyme. The results suggested that denaturants caused very slight conformational changes in the enzyme that perturbed the microenvironment of aromatic amino acid residues such as tryptophan accompanied by reduction or loss of catalytic activity.

Bacteria↗
PubMed1992

COQ2 is a candidate for the structural gene encoding para-hydroxybenzoate:polyprenyltransferase.

Coenzyme Q functions as a lipid-soluble electron carrier in eukaryotes. In Saccharomyces cerevisiae, the enzymes responsible for the assembly of the polyisoprenoid side chain and subsequent transfer to para-hydroxybenzoate (PHB) are encoded by the nuclear genes COQ1 and COQ2, respectively. Yeast mutants defective in coenzyme Q biosynthesis are respiratory defective and provide a useful tool to study this non-sterol branch of the isoprenoid biosynthetic pathway. We isolated a 5.5-kilobase genomic DNA fragment that was able to functionally complement a coq2 strain. Additional complementation analyses located the COQ2 gene within a 2.1-kilobase HindIII-BglII restriction fragment. Sequence analyses revealed the presence of a 1,116-base pair open reading frame coding for a predicted protein of 372 amino acids and a molecular mass of 41,001 daltons. The amino acid sequence exhibits a typical amino-terminal mitochondrial leader sequence and six potential membrane-spanning domains. Primer extension and Northern analyses indicate the gene is transcriptionally active. Transformation of a coq2 strain with the 2.1-kilobase HindIII-BglII genomic restriction fragment on a multicopy plasmid restores PHB:polyprenyltransferase activity to wild-type levels. Disruption of the chromosomal COQ2 gene indicates the gene is not essential for viability, yet is required for PHB:polyprenyltransferase activity and respiratory function. In addition, the deduced amino acid sequence of PHB:polyprenyltransferase contains a putative allylic polyprenyl diphosphate-binding site. The presence of this aspartate-rich domain in a number of functionally distinct proteins which utilize polyprenyl diphosphate substrates is reported.

Alkyl and Aryl Transferases↗
PubMed1986

Inhibitory effect of 3-hydroxybenzo(a)pyrene on the mutagenicity and tumorigenicity of (+/-)-7 beta, 8 alpha-dihydroxy-9 alpha, 10 alpha-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene.

The 12 isomeric phenols of benzo(a)pyrene were tested for their ability to inhibit the mutagenic activity of (+/-)-7 beta, 8 alpha-dihydroxy-9 alpha, 10 alpha-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene [B(a)P 7,8-diol-9,10-epoxide-2], an ultimate mutagenic and carcinogenic metabolite of benzo(a)pyrene. 3-Hydroxybenzo(a)pyrene [3-HO-B(a)P], a major metabolite of benzo(a)pyrene, was the most potent antagonist tested. Approximately 3 nmol of 3-HO-B(a)P, 14 nmol of 10-HO-B(a)P, and 5-8 nmol of 1-, 2-, 4-, 5-, 6-, 7-, 8-, 9-, 11-, and 12-HO-B(a)P inhibited the mutagenic activity of 0.05 nmol of B(a)P 7,8-diol-9,10-epoxide-2 by 50% in Salmonella typhimurium strain TA 100. The importance of the phenolic group for antimutagenic activity was indicated by the lack of antimutagenic activity of benzo(a)pyrene itself. 3-HO-B(a)P also inhibited the mutagenic activity resulting from the metabolic activation of benzo(a)pyrene and (+/-)-trans-7,8-dihydroxy-7,8-dihydrobenzo(a)pyrene by rat liver microsomes. This inhibition may have resulted from an effect of 3-HO-B(a)P on the metabolic activation of these carcinogens and/or from a direct effect on the action of B(a)P 7,8-diol-9,10-epoxide-2. In a mammalian cell culture system utilizing Chinese hamster V79 cells, 3-HO-B(a)P (8 microM) inhibited the mutagenicity of B(a)P 7,8-diol-9,10-epoxide-2 (0.2 microM) by 50%. Although 3-HO-B(a)P was a potent inhibitor of the mutagenic activity of bay-region diol epoxides of benzo(a)pyrene, dibenzo(a,h)pyrene, and dibenzo(a,i)pyrene in S. typhimurium strain TA 100, higher concentrations of 3-HO-B(a)P were needed to inhibit the mutagenicity of the chemically less reactive benzo(a)pyrene 4,5-oxide and the bay-region diol epoxides of benz(a)anthracene, chrysene, and benzo(c)phenanthrene. Both 3-HO-B(a)P and 10-HO-B(a)P accelerated the disappearance of B(a)P 7,8-diol-9,10-epoxide-2 from 1:9 dioxane-water solutions at pH 7 and 25 degrees C. 3-HO-B(a)P, the most effective antimutagen of the B(a)P phenols tested, was much more reactive with the diol epoxide than 10-HO-B(a)P, the least effective antimutagen. The rate constant for the reaction of 3-HO-B(a)P with the diol epoxide exhibited a nonlinear (greater than first-order) dependence on the concentration of the phenol. Evidence was obtained for covalent adduct formation between the diol epoxide and each of the two phenols.(ABSTRACT TRUNCATED AT 400 WORDS)

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1987

Effect of a topical carbonic anhydrase inhibitor, 6-hydroxybenzo[b]thiophene-2-sulfonamide, on intraocular pressure in normotensive subjects.

A prospective randomized clinical trial was carried out to determine the efficacy of 6-hydroxybenzo[b]thiophene-2-sulfonamide, a potent new carbonic anhydrase inhibitor, in lowering intraocular pressure (IOP) in normotensive volunteers. The drug was administered as a 2% suspension twice daily for 1 week to one eye in 10 subjects. Ten other subjects, serving as controls, received a placebo drop to one eye on the same schedule. Subjects and examiners were unaware of whether the drug or placebo was being used. IOP was measured before the study began and twice daily on days 1, 2, 4 and 8 of the study. The drug had no significant effect on IOP. The most likely explanation is failure of an adequate concentration of the drug to reach the ciliary body.

Adult↗
PubMed1986

Pharmacokinetic profile of imidazole 2-hydroxybenzoate, a novel nonsteroidal antiinflammatory agent.

Imidazole 2-hydroxybenzoate is a novel nonsteroidal antiinflammatory agent which clinico-pharmacologically and pharmacokinetically has to be understood as imidazole and salicylic acid. The pharmacokinetic profile of both components after single and multiple oral (tablets, drops), and topical administration (gel 5%)--the latter in a pilot study--was evaluated as well as protein-binding, relative bioavailability and the metabolic pattern. Absorption and elimination of the two compounds were fast. All essential pharmacokinetic and bioavailability parameters seem to be in a good agreement with data published in the literature and an accumulation tendency was not observed. The t1/2 beta for imidazole (oral administration) was determined for a single dose at 2.98 +/- 1.13 h, for a multiple dose (last dose) at 1.86 +/- 0.78 h; for salicylic acid the t1/2 beta for a single dose was determined at 6.46 +/- 3.79 h and for a multiple dose (last dose) at 6.40 +/- 3.36 h. The protein-binding of imidazole was in the range of 5-15% and of salicylic acid of about 80-85%. The relative bioavailability was calculated for imidazole (single dose) at 138% and for multiple dosing (last dose) at 113%; for salicylic acid the values for single dose were 148% and for multiple dosing (last dose) 128%. The tolerability was altogether good and no adverse reactions could be observed. The topical administration (pilot study) with gel 5% did not show any systemic effects or adverse reactions. The local tolerability was very good. Statistically, there were only slight differences between tablets and drops overall since only one p-value was less than 0.01. According to the small sum of squared residuals, the NONLIN-program performed an excellent fitting of the data to the model equation.

Administration, Cutaneous↗
PubMed1984

Reversible inhibition of thromboxane A2 production by imidazole 2-hydroxybenzoate (ITF 182) in the arachidonic acid injected rat. A comparison with acetylsalicylic acid and indometacin.

The behavior of imidazole 2-hydroxybenzoate (ITF 182), acetylsalicylic acid (ASA) and indometacin (INN; in some pharmacopoeias called indomethacin) in inhibiting thromboxane A2 (TXA2) and prostaglandin (PGs) production in the blood of the rat intravenously injected with arachidonic acid was studied. ITF 182 caused a selective inhibition of TXA2 production with a time-dependent reversible action. An irreversible inhibition of PGs production was shown by ASA whereas a reversible inhibition could be observed with indometacin. The PGs involved in the physiological processes, may be spared after ITF 182 administration contrary to what occurs after ASA or indometacin administration.

Animals↗
PubMed1983

On the inhibition of p-hydroxybenzoate hydroxylase from Pseudomonas fluorescens by adenosine nucleotides and metal ion complexes.

The flavoprotein p-hydroxybenzoate hydroxylase is inhibited by adenosine nucleotides, Cibacron blue, phosphate ions and metal ion complexes. The inhibition of the enzyme is competitive with respect to NADPH. The most potent inhibitors of the enzyme are Cibacron blue and the metal ion complexes whereas the inhibition by the adenosine nucleotides is comparable to that by halogen ions. Some inhibitors cause quenching of the fluorescence emission of the protein-bound prosthetic group or perturb the absorption spectrum of the enzyme in the visible region allowing determination of the dissociation constant of the interaction between the free or the substrate-complexed enzyme and the inhibitors. The inhibition constants are in good agreement with the dissociation constants.

Adenine Nucleotides↗
PubMed1984

Penetration of imidazole 2-hydroxybenzoate (ITF 182) into experimentally inflamed pleural and knee joint exudates.

The penetration of the two components of imidazole 2-hydroxybenzoate (ITF 182), imidazole and salicylate, into inflamed sites induced by intrapleural injection of carrageenin in the rat and by a urate-cotton pellet implantation in the knee joint of the rabbit is studied. The results obtained show that the two components of the salt penetrate rapidly the inflamed sites and display different kinetic profiles: imidazole diffuses throughout inflamed and non-inflamed fluids without any specific localization, salicylate shows preferential localization in inflamed fluids and remains longer than imidazole.

Animals↗
PubMed1984

Different sensitivity of basilar and saphenous arteries to thromboxane A2-induced contractions. Effect of imidazole 2-hydroxybenzoate (ITF 182).

Superfused rings of rabbit basilar arteries are more sensitive than those of saphenous arteries to the contractions induced by a prostaglandin endoperoxide analogue (U-46 619) and by a thromboxane A2 (TXA2) generating system. 5-Hydroxytryptamine aggravates the latter. Prostaglandin I2 (PGI2) on the other hand, relaxes only the basilar rings without affecting the saphenous. Imidazole 2-hydroxybenzoate (ITF 182), at doses that do not interfere with platelet cyclooxygenase, reduces the contractions induced by the TXA2 generating system on both arteries because it reduces the platelet TXA2 synthetase enzyme. TXA2 is involved in the aetiology of strokes and cerebral vasospasms while PGI2 plays a physiological role in the maintenance of cerebral arterial tone. The high sensitivity of cerebral arteries to contractures caused by TXA2 together with the ability of ITF 182 to reduce them by inhibiting TXA2 production and to spare physiological PG production suggest a beneficial effect of the drug in cerebral vasospasms.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1981

High pressure liquid chromatographic determination of methyl and propyl p-hydroxybenzoates in comminuted meats.

A method was developed for determining methyl and propyl p-hydroxybenzoates (methyl and propyl parabens) in comminuted meats. The parabens were extracted from the meat sample with acetonitrile. After filtering, the extract was analyzed by reverse phase high pressure liquid chromatography, using a 254 nm absorbance detector. Samples of bologna, chicken roll, and chopped ham were fortified with approximately 100, 200, and 400 ppm of each paraben. Average recoveries were 92% for methyl paraben and 94% for propyl paraben.

Animals↗
PubMed1977

Micro-determination of p-hydroxybenzoic esters in pharmaceuticals and cosmetics.

A rapid and specific method is described for the determination of microamounts of methyl, propyl, and butyl p-hydroxybenzoic esters (parabens) in pharmaceuticals and cosmetics. The method involves the direct extraction of parabens into benzene or chloroform followed by derivatization with phosphorochloridate. The diethyl phosphate ester derivatives are cleaned up on a Florisil minicolumn and finally measured by gas-liquid chromatography on 5% OV-210 on Gas-Chrom Q. A flame photometric detector or a KCl thermionic detector may be used. The concentration response was linear up to 40 ng parabens. The reproducibility and margin or error were tested with fortified samples. This method may be applied to the estimation of other phenol derivatives.

Chromatography, Gas↗
PubMed1993

Cloning, nucleotide sequence, and expression of a p-hydroxybenzoate hydroxylase isozyme gene from Pseudomonas fluorescens.

A gene encoding for a putative isozyme of p-hydroxy-benzoate hydroxylase (PHBH) has been isolated from Pseudomonas fluorescens (ATCC 13525). A comparison of the translated amino acid sequence with that of the known PHBH from P. fluorescens revealed that the new enzyme contains 3 additional amino acids and has 73% absolute homology to the previously known enzyme; conservation of secondary and active-site structures implied that the isozyme and known enzyme share the same general tertiary structure. Subsequent expression of the isozyme in Escherichia coli produced an enzyme with a specific activity about half that of the previously characterized PHBHs from P. fluorescens and Pseudomonas aeruginosa; in addition, somewhat weaker binding affinities for both NADPH and p-hydroxybenzoate were observed. Speculations are made on the reason for the existence of the isozyme, which does not appear to be expressed routinely in P. fluorescens.

Amino Acid Sequence↗
PubMed1984

pH dependence of the reoxidation of p-hydroxybenzoate hydroxylase 2,4-dihydroxybenzoate complex.

Oxidation of reduced p-OH-benzoate hydroxylase . 2,4-diOH-benzoate complex by molecular oxygen occurs in four clearly defined steps. Inclusion of azide in the reaction medium slows the rate for each step. We have found that the rates for the last three steps as well as the UV/visible absorbance spectrum for the second intermediate are markedly dependent on pH. Formation of intermediate II is base-catalyzed while its decay to intermediate III is acid-catalyzed. Formation of oxidized enzyme from intermediate III is base-catalyzed. The spectrum of intermediate II is shifted to longer wavelengths on raising the pH. A pKa of about 7.8 can be calculated for each of these pH-dependent transitions, except for the rate of formation of oxidized enzyme. This rate appears to be directly dependent on hydroxide ion concentration. The presence of azide does not change the observed pH dependence. These results are discussed in the context of a 4a,5-ring opened flavin structure for intermediate II.

4-Hydroxybenzoate-3-Monooxygenase↗