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PubMed1996

Half-fraction and full factorial designs versus central composite design for retention modelling in reversed-phase ion-pair liquid chromatography.

In a previous paper (J. O. De Beer, C. V. Vandenbroucke and D. L. Massart, J. Pharm. Biomed. Anal., 12, (1994) 1379-1396) liquid chromatographic (LC) retention modelling of the cough-syrup compounds methyl para-hydroxybenzoate (MPHB) and propyl para-hydroxybenzoate (PPHB), phenylephrine hydrochloride (PE) and chlorphenamine maleate (CPM) was studied using a face-centred central composite design. It is examined whether smaller half-fractional and full factorial designs with fewer experiments tend to reliably predict retention times of the latter compounds as well. Simplified regression modelling, however, neglecting more first-order and interactive effects and disregarding pure second-order effects, has to be set up. These smaller designs finally satisfy the prediction of the retention of MPHB, PPHB and PE also. Retention prediction of CPM is much less accurate. CPM has a pKa value of 4.0, which is encompassed by the examined mobile phase pH limits 3.0 and 5.0. Since the largest retention shifts occur near the pKa value, retention prediction in this area becomes more complex. CPM retention modelling from a full factorial design is useful if the mobile phase pH is fixed at 5.0 for methanol as well as for acetonitrile as organic modifers. The full factorial design, applied with acetonitrile as organic modifer, enables the selection of suitable LC parameter combinations for fast and complete separation of the four compounds in cough-syrup analysis.

Chemical Phenomena↗
PubMed1989

Preservatives in the vehicle of naloxone: pharmacological effects.

The pharmacological activity of the preservatives methyl and propyl hydroxybenzoate, until recently components of the vehicle of naloxone (Narcan), was investigated in vitro. This vehicle produced reversible, concentration-dependent relaxation of guinea pig trachea, not mediated via adrenergic or cholinergic receptors, prostanoid activity or phosphodiesterase inhibition. Sensitivity of the tissue to calcium-induced contraction was decreased. In single isolated rat hepatocytes, surface receptor stimulation elicits repetitive transient rises in intracellular free calcium measured with the photoprotein aequorin. The vehicle reversibly inhibited these transients. These observations suggest that the effect of hydroxybenzoates may be mediated via a perturbation of intracellular calcium-related processes.

Aequorin↗
PubMed2005

Molecular characterization of cytochrome P450 catalyzing hydroxylation of benzoates from the white-rot fungus Phanerochaete chrysosporium.

We cloned full-length cDNA (PcCYP1f) encoding one of the cytochrome P450s in the lignin-degrading basidiomycete Phanerochaete chrysosporium, which showed high homology to P450s in the CYP53 family. PcCYP1f was expressed as an active microsomal protein using the methylotrophic yeast Pichia pastoris expression system. Using the microsomal fraction containing PcCYP1f, a typical P450 CO-difference spectrum was obtained with absorption maximum at 448nm. Recombinant PcCYP1f catalyzed the hydroxylation of benzoic acid into 4-hydroxybenzoic acid in the presence of NADPH and P. chrysosporium cytochrome P450 oxidoreductase. In contrast to other CYP53 P450s, this enzyme was shown to catalyze the hydroxylation of 3-hydroxybenzoate into 3,4-dihydroxybenzoate. Furthermore, 2- and 3-methylbenzoate were also shown to be substrates of PcCYP1f. This is the first report showing the expression of a functionally active Phanerochaete P450. Finally, real-time quantitative PCR analysis revealed that PcCYP1f is induced at a transcriptional level by exogenous addition of benzoic acid.

Amino Acid Sequence↗
PubMed2004

Kinetic and structural consequences of the leaving group in substrates of a class C beta-lactamase.

The class C beta-lactamase of Enterobacter cloacae P99 is known to catalyze the hydrolysis of certain acyclic (thio)esters. Previous experiments have employed thioglycolate, m-hydroxybenzoate, and phenylphosphate leaving groups. The relative effectiveness of these leaving groups has now been quantitatively assessed by employment of a series of compounds with common acyl groups, and found to rank in the order phenylphosphate >m-hydroxybenzoate >thioglycolate. Structural models suggest that these leaving groups interact during acylation principally with Tyr 150, Lys 315, and Thr 316 of the beta-lactamase active site. The positions of the leaving group carboxylates in these models is compared with those in published crystal structures of complexes of class C beta-lactamases with beta-lactams. The particular effectiveness of the acyl phosphate indicates the positions of two oxyanions that strongly interact with the active site. This information should be useful in the design of inhibitors of class C beta-lactamases.

Acylation↗
PubMed2004

In vitro and in vivo production of new aminocoumarins by a combined biochemical, genetic, and synthetic approach.

The aminocoumarin antibiotics clorobiocin, novobiocin, and coumermycin A(1) are inhibitors of bacterial gyrase. Their chemical structures contain amide bonds, formed between an aminocoumarin ring and an aromatic acyl component, which is 3-dimethylallyl-4-hydroxybenzoate in the case of novobiocin and clorobiocin. These amide bonds are formed under catalysis of the gene products of cloL, novL, and couL, respectively. We first examined the substrate specificity of the purified amide synthetases CloL, NovL, and CouL for the various analogs of the prenylated benzoate moiety. We then generated new aminocoumarin antibiotics by feeding synthetic analogs of the 3-dimethylallyl-4-hydroxybenzoate moiety to a mutant strain defective in the biosynthesis of the prenylated benzoate moiety. This resulted in the formation of 32 new aminocoumarin compounds. The structures of these compounds were elucidated using FAB-MS and (1)H-NMR spectroscopy.

Amide Synthases↗
PubMed2005

Effects of polyelectrolytes on reduction of model compounds via coagulation.

The objective of this research work was to evaluate the performance of enhanced coagulation by alum and polymer. Synthetic source waters containing high molecular weight humic acids, medium molecular weight tannic acids and low molecular weight p-hydroxybenzoic acid were formulated by adjusting the concentration of turbidity and pH; and jar tests were used to study the effect of various types and dosages of polymer on reducing the above model compounds. At a specific pH condition, the applied alum dosage would efficiently decrease the turbidity to 2 NTU follows the order: humic>tannic>p-hydroxybenzoic acid. Adjustment of pH influenced the performance of alum obviously but not of p-DADMAC. High p-DADMAC dosage overwhelming the effects of alum is less affected by pH adjustment. The results of this investigation reveal that enhanced coagulation with p-DADMAC was founded to be very effective for removing high-molecular-weight THM precursors, i.e., humic acid and tannic acid, and markedly reduced the alum dosages required for turbidity removal. The other two polymers, i.e., cationic PAM and non-ionic PAM, which had higher molecular weight but lower charge density than p-DADMAC, were not capable of removing organic precursors. It was thus concluded that enhanced coagulation with polymer, p-DADMAC, could be considered as a promising technique for removal of NOMs with hydrophobic and higher-molar-mass (>1K) in water treatment plants.

Air Pollutants↗
PubMed2006

SanJ, an ATP-dependent picolinate-CoA ligase, catalyzes the conversion of picolinate to picolinate-CoA during nikkomycin biosynthesis in Streptomyces ansochromogenes.

Nikkomycins, a group of peptidyl nucleoside antibiotics, are competitive inhibitors of chitin synthase. The nikkomycin biosynthetic gene cluster has been cloned previously from Streptomyces ansochromogenes. The cluster contains 25 complete ORFs including sanJ. The sanJ gene was inactivated by the insertion of a kanamycin resistance gene and the resulting disruption mutants failed to produce nikkomycins. Moreover, the nikkomycin production was restored by complementation with a single copy of sanJ. The deduced product of sanJ bears striking sequence similarity with enzymes belonging to the adenylate-forming superfamily. sanJ was overexpressed as a His6-tagged fusion protein in Escherichia coli and purified to apparent homogeneity by affinity chromatography. The purified SanJ demonstrated adenylate ligase activity in the presence of picolinate or its analogs (benzoate, nicotinate, 4-methoxybenzoate, 4-hydroxybenzoate), ATP and Mg2+. SanJ was also found to catalyze the conversion of picolinate, benzoate, nicotinate to their corresponding CoA esters and 4-methoxybenzoate, 4-hydroxybenzoate to their respective AMP derivatives in vitro. This was unambiguously shown by using HPLC and electrospray ionization mass spectrometry (ESI-MS) or by comparing the reaction product with an authentic standard of benzoyl-CoA. These results indicated that sanJ encodes an ATP-dependent picolinate-CoA ligase which is essential for nikkomycin biosynthesis.

Adenosine Triphosphate↗
PubMed2002

Enhanced detection and characterization of protocatechuate 3,4-dioxygenase in Acinetobacter lwoffii K24 by proteomics using a column separation.

Acinetobacter lwoffii K24 known as an aniline degrading bacterium has also been found to utilize p-hydroxybenzoate as a sole carbon source. In this study, 2-DE using Q-Sepharose column separation was attempted for fast screening of protocatechuate 3,4-dioxygenase for catabolism of p-hydroxybenzoate in A. lwoffii K24. Two protocatechuate 3,4-dioxygenase subunits, pcaG and pcaH were detected and identified with N-terminal and internal sequencing, suggesting proteomics using a column separation may be helpful for the identification of specific protein spots and maximizing the detectable protein spots on the 2-DE gel. The PCR process using degenerate primers for protocatechuate 3,4-dioxygenase and sequence analyses of the PCR products revealed the existence of pcaH and pcaG in A. lwoffii K24. These two subunits were found to be closely located and share extensive homology with pcaH and pcaG of Pseudomonas marginata or Pseudomonas cepacia, providing the evidence that A. lwoffi K24 has the protocatechuate branches as well as catechol branches of beta-ketoadipate pathway.

Acinetobacter↗
PubMed2000

Mechanism for the peroxynitrite scavenging activity by anthocyanins.

We show that anthocyanins can function as potent inhibitors of the formation of nitrated tyrosine in vitro, and clarified how pelargonidin (Pel), which has a mono-hydroxyl group on the B-ring, can scavenge peroxynitrite (ONOO(-)) by detection of the reaction products. Pel was reacted with ONOO(-), then the reaction mixture was analyzed using high-performance liquid chromatography (HPLC). The HPLC analyses showed two novel peaks assumed to be the reaction products. Based on the instrumental analyses, the reaction products were identified as p-hydroxybenzoic acid and 4-hydroxy-3-nitrobenzoic acid. Pel can protect tyrosine from undergoing nitration through the formation of p-hydroxybenzoic acid and 4-hydroxy-3-nitrobenzoic acid.

Anthocyanins↗
PubMed1988

Simultaneous determination of the nine food additives using high-performance liquid chromatography.

A technique for the simultaneous determination of sorbic acid, benzoic acid, dehydroacetic acid, p-hydroxybenzoic acid esters (ethyl, isopropyl, n-propyl, isobutyl and n-butyl p-hydroxybenzoate) and saccharin sodium using ion-pair reversed-phase high-performance liquid chromatography is described. The nine food additives were separated on a Nucleosil 3C18 (3 microns) column (75 x 4.6 mm I.D.) using methanol-acetonitrile-0.05 M aqueous acetonic acid solution (pH 4.5) (1.5:1:3.1) containing 2.5 mM cetyltrimethylammonium chloride as the mobile phase at a flow-rate of 1.0 ml/min, and detected at 233 nm. The food additives were separated within 18 min and their calibration graphs were linear between 2 and 200 ng.

Acetonitriles↗
PubMed1976

Study of the intestinal tyrosine metabolism using stable isotopes and gas chromatography-mass spectrometry.

Deuterated tyrosine, 4-hydroxyphenyllactic acid, 4-hydroxyphenylpropionic acid, 4-hydroxyphenylacetic acid and 4-hydroxybenzoic acid were incubated under anaerobic conditions with human faecal specimens for the in vitro study of their respective metabolisms. After 1 week, aromatic acids and phenols were extracted and analyzed by gas chromatography-mass spectrometry. [3',5'-2H2]Tyrosine produced 4-hydroxyphenyllactic acid, 4-hydroxyphenylpropionic acid and 4-hydroxyphenylacetic acid; [3',5'-2H2]-4'-hydroxyphenyllactic acid produced 4-hydroxyphenylpropionic acid, 3-hydroxyphenylpropionic acid, 4-hydroxyphenylacetic acid and phenylproionic acid; [3',5'-2H2]-4'-hydroxyphenyl-propionic acid produced 3-hydroxyphenylpropionic acid and phenylpropionic acid; [3',5',2,2-2H4]-4'-Hydroxyphenylacetic acid produced p-cresol; and [3',5'-2H2]-4'-hydroxybenzoic acid produced phenol. Thus the intestinal flora showed activities for decarboxylation leading to phenol and p-cresol, dehydroxylation leading to phenylpropionic acid and rearrangement leading to 3-hydroxyphenylpropionic acid. Rentention of both deuterium labels was observed in the rearrangement reaction.

Anaerobiosis↗
PubMed2003

Separation and identification of photodegradation products of benzoic acid by capillary zone electrophoresis.

A capillary zone electrophoresis (CZE) method was developed for separation and identification of photodegradation products of benzoic acid under irradiation at a wavelength of 300 nm. Parameters such as run buffer, applied voltage and injection time were optimized for the separation of benzoic acid and its photodegradation products. Linearity, limit of detection, and repeatability of migration time as well as peak area of the method were examined. Four reaction products, including salicylic acid, 3-hydroxybenzoic acid, 4-hydroxybenzoic acid and 3,4-dihydroxybenzoic acid have been separated and identified by spiking the known compounds into the irradiated samples using the CZE method developed. The confirmation of the reaction products is one of the key steps for proposing the possible reaction mechanisms involved in the photodegradation of benzoic acid.

Benzoic Acid↗
PubMed1999

Simultaneous determination of antioxidants, preservatives and sweeteners permitted as additives in food by mixed micellar electrokinetic chromatography.

A micellar electrokinetic chromatography method was developed to simultaneously analyse commonly used food additives. The additive mixture, comprising propyl gallate, octyl gallate, dodecyl gallate, butylated hydroxyanisole, butylated hydroxytoluene, tertiary butylhydroquinone, p-hydroxybenzoic acid methyl ester, p-hydroxybenzoic acid ethyl ester, benzoic acid, sorbic acid, saccharin, aspartame and acesulfame-K, was not resolved using single surfactant micellar systems consisting of sodium dodecyl sulfate (SDS), sodium cholate (SC) or sodium deoxycholate (SDC). The separation of these additives using mixed micellar systems, involving SDS/SC, SDS/SDC and SC/SDC, was investigated. Organic solvents were added to the mixed micellar phases to optimise the separation. The mixture was successfully separated using a 20 mM borate buffer with 35 mM SC, 15 mM SDS and 10% methanol added at pH 9.3. Additives in cola beverages and low-joule jam were investigated and quantified using this method.

Antioxidants↗
PubMed2000

Effect of a dioxin-like PCB (CB 126) on the biotransformation and genotoxicity of benzo

Two experiments were performed to study the interaction between benzo[a]pyrene (BaP) and the planar, dioxin-like PCB congener 3,3',4,4',5-pentachlorobiphenyl (CB 126) in the flatfish dab (Limanda limanda). The first experiment involved four groups. Group I was treated with 10 µg/kg CB 126, group II was treated with 2 mg/kg BaP, group III was first treated with 10 µg/kg CB 126 and exposed to 2 mg/kg BaP 6 days later, and group IV was a control group. The second experiment was similar, except that the BaP dosage level was increased to 50 mg/kg. Pre-treatment with 10 µg/kg of CB 126 always caused the induction of hepatic cytochrome P450 1A (CYP1A), as measured by significant increases of the model reaction 7-ethoxyresorufin-O-deethylase (EROD) in microsomal preparations. Treatment of dab with BaP caused a significant EROD induction at the 50 mg/kg, but not at the 2 mg/kg level. Concurrent with EROD induction by either CB 126 or 50 mg/kg BaP, was a significant change in the biliary metabolite pattern in favour of 1-hydroxybenzo[a]pyrene and 3-hydroxybenzo[a]pyrene and towards a lower fraction of the procarcinogen BaP-7,8-dihydrodiol (7,8-DIOL). Pre-treatment with CB 126 did not cause an increase of hepatic BaP DNA adducts formed after treatment with either 2 or 50 mg/kg BaP. Glutathione S-transferase (GST) activities remained also unaffected by any of the treatments. The results of this study suggest that the pattern of BaP metabolites in bile depends on the level of CYP1A induction. Moreover, the concurrence of a potent CYP1A inducer and BaP does not necessarily lead to an increase in DNA adduct levels in liver tissue. The observation that the level of 7,8-DIOL is decreased despite a higher (CYP1A mediated) EROD activity explains, at least in part, the lack of induction of DNA adducts.

Journal Article↗
PubMedDate not supplied

The nature of salicylate inhibition of sugar transport in yeast.

A study was made in yeast of the cellular site associated with inhibition of sugar transport by salicylate. Time-course and stereospecificity studies were done on the uptake of salicylic acid (sal), meta-hydroxybenzoic acid (m-OH), D-glucose (gluc) and 3-0-methyl-D-glucose (3-OMG) at 20 and 30 degrees C. Sal added simultaneously with 3-OMG had little effect on initial uptake rates of the latter. Inhibition of 3-OMG transport occurred only after appreciable uptake of sal. Rates of glucose utilization in cells preincubated with sal increased with time despite increased drug in the medium as sal decreased in the cells. Benzoic acid also inhibited 3-OMG transport. m-OH or para-hydroxybenzoic acid entered cells but neither substance inhibited 3-OMG transport nor affected the inhibition by sal of 3-OMG transport. Benzyl and salicyl alcohols had no effect on 3-OMG transport. The results indicate a stereospecific binding site or sites for sal located in the cell interior and associated with inhibition of sugar transport. The known inhibition of sugar transport by sal in susceptible mammalian cells, including human cells, may also occur through binding of sal to intracellular, stereospecific sites.

3-O-Methylglucose↗
PubMed2001

Safety assessment of propyl paraben: a review of the published literature.

Propyl paraben (CAS no. 94-13-3) is a stable, non-volatile compound used as an antimicrobial preservative in foods, drugs and cosmetics for over 50 years. It is an ester of p-hydroxybenzoate. Propyl paraben is readily absorbed via the gastrointestinal tract and dermis. It is hydrolyzed to p-hydroxybenzoic acid, conjugated and the conjugates are rapidly excreted in the urine. There is no evidence of accumulation. Acute toxicity studies in animals indicate that propyl paraben is relatively non-toxic by both oral and parenteral routes, although it is mildly irritating to the skin. Following chronic administration, no-observed-effect levels (NOEL) as high as 1200-4000 mg/kg have been reported and a no-observed-adverse-effect level (NOAEL) in the rat of 5500 mg/kg is posited. Propyl paraben is not carcinogenic, mutagenic or clastogenic. It is not cytogenic in vitro in the absence of carboxyesterase inhibitors. The mechanism of propyl paraben may be linked to mitochondrial failure dependent on induction of membrane permeability transition accompanied by the mitochondrial depolarization and depletion of cellular ATP through uncoupling of oxidative phosphorylation. Sensitization has occurred when medications containing parabens have been applied to damaged or broken skin. Parabens have been implicated in numerous cases of contact sensitivity associated with cutaneous exposure, but high concentrations of 5-15% in patch testing are needed to elicit reaction in susceptible individuals. Allergic reactions to ingested parabens have been reported, although rigorous evidence of the allergenicity of ingested paraben is lacking.

Animals↗
PubMed2002

Evaluation of the health aspects of methyl paraben: a review of the published literature.

Methyl paraben (CAS No. 99-76-3) is a methyl ester of p-hydroxybenzoic acid. It is a stable, non-volatile compound used as an antimicrobial preservative in foods, drugs and cosmetics for over 50 years. Methyl paraben is readily and completely absorbed through the skin and from the gastrointestinal tract. It is hydrolyzed to p-hydroxybenzoic acid, conjugated, and the conjugates are rapidly excreted in the urine. There is no evidence of accumulation. Acute toxicity studies in animals indicate that methyl paraben is practically non-toxic by both oral and parenteral routes. In a population with normal skin, methyl paraben is practically non-irritating and non-sensitizing. In chronic administration studies, no-observed-effect levels (NOEL) as high as 1050 mg/kg have been reported and a no-observed-adverse-effect level (NOAEL) in the rat of 5700 mg/kg is posited. Methyl paraben is not carcinogenic or mutagenic. It is not teratogenic or embryotoxic and is negative in the uterotrophic assay. The mechanism of cytotoxic action of parabens may be linked to mitochondrial failure dependent on induction of membrane permeability transition accompanied by the mitochondrial depolarization and depletion of cellular ATP through uncoupling of oxidative phosphorylation. Parabens are reported to cause contact dermatitis reactions in some individuals on cutaneous exposure. Parabens have been implicated in numerous cases of contact sensitivity associated with cutaneous exposure; however, the mechanism of this sensitivity is unknown. Sensitization has occurred when medications containing parabens have been applied to damaged or broken skin. Allergic reactions to ingested parabens have been reported, although rigorous evidence of the allergenicity of ingested paraben is lacking.

Animals↗
PubMed1999

Rapid and sensitive determination of paclitaxel in mouse plasma by high-performance liquid chromatography.

This report describes a rapid, simple and sensitive isocratic high-performance liquid chromatography with diode array UV detection for micro-sample analysis of paclitaxel in mouse plasma. The analysis utilized a Capcell-pak octadecyl analytical column and a mobile phase consisting of acetonitrile--0.1% phosphoric acid in deionized water (55:45, v/v). Paclitaxel and n-hexyl p-hydroxybenzoic acid (internal standard) were extracted from plasma by one-step extraction with tert.-butyl methyl ether. Peak purity was determined over a UV wavelength range of 200 to 400 nm. Paclitaxel and the internal standard were eluted at 3.4 min and 5.4 min, respectively, at a mobile phase flow-rate of 1.3 ml/min. No interfering peaks were observed and the total run time was 10 min. The standard curve was linear (r = 0.9999) over the concentration range of 0.010-500 micrograms/ml. The extraction recovery was > 90% for both paclitaxel and n-hexyl p-hydroxybenzoic acid. The intra- and inter-day assay variabilities of paclitaxel ranged from 0.4 to 2.2% and 0.6 to 7.8%, respectively. The LOD and LOQ were 5 and 10 ng/ml, respectively, for paclitaxel using a plasma sample volume of 100 microliters. This highly sensitive and simple assay method was successfully applied to a pharmacokinetic study after i.v. administration of paclitaxel 20 mg/kg to mice.

Animals↗