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At least 1,135 records · Page 63Linked to original sources
PubMed1998

Aromatic DNA adducts in human white blood cells and skin after dermal application of coal tar.

A group of eczema patients topically treated with coal tar (CT) ointments was used as a model population to examine the applicability of DNA adducts in WBC subpopulations as a measure of dermal exposure to polycyclic aromatic hydrocarbons (PAHs). Aromatic DNA adducts were examined by 32P-postlabeling in exposed skin and WBC subsets, and urinary excretion of PAH metabolites was determined to assess the whole-body burden. The median urinary excretion of 1-hydroxypyrene and 3-hydroxybenzo(a)pyrene was 0.39 (range, 0.12-1.57 micromol/mol creatinine) and 0.01 micromol/mol creatinine (range, <0.01-0.04 micromol/mol creatinine), respectively, before the dermal application of CT ointments. After treatment for 1 week, these levels increased to 139.7 (range, 26.0-510.5 micromol/mol creatinine) and 1.18 micromol/mol creatinine (range, <0.01-2.14 micromol/mol creatinine), respectively, indicating that considerable amounts of PAHs were absorbed. Median aromatic DNA adduct levels were significantly increased in skin from 2.9 adducts/10(8) nucleotides (nt; range, 0.7-10.0 adducts/10(8) nt) before treatment to 63.3 adducts/10(8) nt (range, 10.9-276.2 adducts/10(8) nt) after treatment with CT, in monocytes from 0.28 (range, 0.25-0.81 adducts/10(8) nt) to 0.86 adducts/10(8) nt (range, 0.56-1.90 adducts/10(8) nt), in lymphocytes from 0.33 (range, 0.25-0.89 adducts/10(8) nt) to 0.89 adducts/10(8) nt (range, 0.25-3.01 adducts/10(8) nt), and in granulocytes from 0.28 (range, 0.25-0.67 adducts/10(8) nt) to 0.54 adducts/10(8) nt (range, 0.25-1.58 adducts/10(8) nt). A week after stopping the CT treatment, the DNA adduct levels in monocytes and granulocytes were reduced to 0.38 (range, 0.25-0.71 adducts/10(8) nt) and 0.38 adducts/10(8) nt (range, 0.25-1.01 adducts/10(8) nt), respectively, whereas the adduct levels in lymphocytes remained enhanced [1.59 adducts/10(8) nt (range, 0.25-2.40 adducts/10(8) nt)]. Although the adduct profiles in skin and WBC subsets were not identical, and the adduct levels in WBCs were significantly lower as compared with those in skin, the total DNA adduct levels in skin correlated significantly with the adduct levels in monocytes and lymphocytes, but not with those in granulocytes. Excretion of urinary metabolites during the first week of treatment was correlated with the percentage of the skin surface treated with CT ointment and decreased to background levels within a week after the cessation of treatment. 3-Hydroxybenzo(a)pyrene excretion, but not that of 1-hydroxypyrene, correlated significantly with the levels of DNA adducts in skin that comigrated with benzo(a)pyrene-diol-epoxide-DNA. This study indicates that the DNA adduct levels in mononuclear WBCs can possibly be used as a surrogate for skin DNA after dermal exposure to PAHs.

Administration, Cutaneous↗
PubMed2001

Comparing protein-ligand interactions in solution and single crystals by Raman spectroscopy.

By using a Raman microscope, we show that it is possible to probe the conformational states in protein crystals and crystal fragments under growth conditions (in hanging drops). The flavin cofactor in the enzyme para-hydroxybenzoate hydroxylase can assume two conformations: buried in the protein matrix ("in") or essentially solvent-exposed ("out"). By using Raman difference spectroscopy, we previously have identified characteristic flavin marker bands for the in and out conformers in the solution phase. Now we show that the flavin Raman bands can be used to probe these conformational states in crystals, permitting a comparison between solution and crystal environments. The in or out marker bands are similar for the respective conformers in the crystal and in solution; however, significant differences do exist, showing that the environments for the flavin's isoalloxazine ring are not identical in the two phases. Moreover, the Raman-band widths of the flavin modes are narrower for both in and out conformers in the crystals, indicating that the flavin exists in a more limited range of closely related conformational states in the crystal than in solution. In general, the ability to compare detailed Raman data for complexes in crystals and solution provides a means of bridging crystallographic and solution studies.

4-Hydroxybenzoate-3-Monooxygenase↗
PubMedDate not supplied

[para-Aminobenzoic acid as a sole source of carbon and energy for Pseudomonas desmoliticum].

A strain of Psuedomonas desmoliticum has been isolated from soil. It utilizes, as a source of carbon and energy, p-aminobenozic (PABA), p-fluorobenzoic acids, and some other aromatic compounds. The strain has been isolated by inoculating soil suspensions onto Petri plates with a solid mineral medium containing 0.1% PABA as a carbon source. The preparatory metabolism of PABA was studied in this work; p-hydroxybenzoic and protocatechuic acids were found to be its intermediate products. Enzyme systems catalysing oxidation of aromatic compounds and glucose are inducible.

4-Aminobenzoic Acid↗
PubMed2000

Quenched phosphorescence, a new detection method in capillary electrophoresis.

The applicability of quenched phosphorescence as a detection mode in capillary electrophoresis (CE) was explored for a number of analyte classes and buffer systems. The detection method is based on the quenching of biacetyl phosphorescence (biacetyl is a constituent of the CE buffer) by the analytes via various mechanisms (energy transfer, electron transfer and, possibly, hydrogen donation) and gives rise to negative peaks in the electropherograms. A number of buffers in the pH range 4.7-11.5, frequently used in CE, were tested for their compatibility with this detection mode. Borate, succinate, malonate, acetate, and phosphate buffers (pH 4.7-8.5) could be used without any problems. With a pH of ca. 8.5 or higher the baseline declined with time, while at a pH higher than 9.5 no signal at all was obtained. Obviously, the noise on the phosphorescence signal (i.e., the baseline) determines the ultimate analyte detection limits (LODs). The baseline signal-to-noise ratio, usually denoted as the dynamic reserve (DR), was enhanced ca. 25-fold compared to direct biacetyl excitation by sensitization of the biacetyl phosphorescence by 1,5-naphthalenedisulfonic acid, and by application of a total emission mirror (TEM). A concentration of 1 x 10(-3) M 1,5-naphthalenedisulfonic acid was found to be optimal. For the buffer systems considered, the DR was typically ca. 300-600 under optimized conditions (noise defined as 1 x sigma). Investigated analytes include naphthalenesulfonic acids (NS), nitrophenols, hydroxybenzoic acids, amino acids, and dithiocarbamates (DTCs.). For most of these, the LODs were in the 10(-7)-10(-8) M range, which is significantly lower than with direct or indirect absorption detection.

Amino Acids↗
PubMed2002

Collective vibrational modes in biological molecules investigated by terahertz time-domain spectroscopy.

We present well-resolved absorption spectra of biological molecules in the far-IR (FIR) spectral region recorded by terahertz time-domain spectroscopy (THz-TDS). As an illustrative example we discuss the absorption spectra of benzoic acid, its monosubstitutes salicylic acid (2-hydroxy-benzoic acid), 3- and 4-hydroxybenzoic acid, and aspirin (acetylsalicylic acid) in the spectral region between 18 and 150 cm(-1). The spectra exhibit distinct features originating from low-frequency vibrational modes caused by intra- or intermolecular collective motion and lattice modes. Due to the collective origin of the observed modes the absorption spectra are highly sensitive to the overall structure and configuration of the molecules, as well as their environment. The THz-TDS procedure can provide a direct fingerprint of the molecular structure or conformational state of a compound.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2007

Determination of paclitaxel in human and rat blood samples after administration of low dose paclitaxel by HPLC-UV detection.

A simple and sensitive HPLC-UV method was developed for the determination of paclitaxel (TXL) in human and rat blood samples. 4-Hydroxybenzoic acid n-hexyl ester was used as an internal standard. TXL was extracted by a liquid-liquid extraction with tert-butylmethyl ether. The disturbing peaks in the case of serum sample were removed by pre-extraction with hexane. The separation of TXL was achieved within 25 min using an ODS column with 50% acetonitrile aqueous solution as a mobile phase at a flow rate of 1.0 mL/min. The eluent was monitored at 230 nm, and the resulted retention times of TXL and IS were 11.2 and 20.4 min. The detection limits of TXL for human plasma, serum and rat plasma samples at a signal-to-noise ratio of 3 were 10, 9.5 and 7.5 ng/mL, respectively. The proposed methods were applicable to the determination of TXL in human patients' plasma ranging from 15 to 27 ng/mL. Furthermore, monitoring of the time course of TXL after its single administration to rat could be demonstrated.

Aged↗
PubMed1983

Phenolic acids in oilseed flours.

Noticeable quantitative differences were found in the content of free and bound phenolic acids in flours obtained from soybeans, cottonseed, peanuts, rapeseed, white mustard, flax and sesame seeds. Independently of the type of seeds used to produce flour, the highest amounts of acids were liberated from ester bonds. These acids were especially abundant in flour made from rape and white mustard seeds. Phenolic compounds identified in these flours were predominated by sinapic and p-hydroxybenzoic acids and in the other flours by other phenolic acids.

Flour↗
PubMed2003

Hydroxyl radical formation is greater in striatal core than in penumbra in a rat model of ischemic stroke.

Although hydroxyl radical ((*)OH) formation has been implicated in the pathophysiological changes of ischemic stroke, (*)OH production in the core and penumbra regions is not clear. It is extremely important to distinguish penumbra from ischemic core in focal cerebral ischemia studies, because the penumbra contains viable tissue, which can be salvaged by appropriate treatment. This study evaluated (*)OH production in both core and penumbra regions of ischemic striatum during ischemia and reperfusion. Microdialysis probes were placed in striatal tissue of rats subjected to the middle cerebral artery occlusion model of ischemic stroke. The (*)OH-trapping agent 4-hydroxybenzoic acid (4-HBA) was administered by both i.v. and probe infusion. Dialysate levels of the 4-HBA oxidation products, 3,4-dihydroxybenzoic acid (3,4-DHBA), were determined by HPLC-ECD. After microdialysis probe delivery of 4-HBA, (*)OH production was significantly increased in the striatal core during both ischemia and reperfusion. Penumbra (*)OH production increased only during reperfusion. Alterations of 3,4-DHBA concentration in dialysate following i.v. 4-HBA administration were likely related to alterations in tissue blood flow. The findings were confirmed by a greater oxidation of dihydroethidium in the ischemic core than in the penumbra as determined by fluorescent microscopy. The findings of (*)OH production in ischemic striatum are the opposite of those reported for ischemic cortex and suggest critical regional variations in (*)OH production that may have significant clinical implications in the treatment of ischemic stroke.

Animals↗
PubMed1992

Effect of cosubstrates on the dechlorination of selected chlorophenolic compounds by Rhodococcus erythropolis 1CP.

Effects of aromatic and nonaromatic cosubstrates on the rate of 2,4-dichlorophenol degradation by R. erythropolis 1CP were studied under growth and nongrowth conditions. Glucose and maltose were found to accelerate 2,4-dichlorophenol (initial conc. 50 mg/l) dechlorination from 11 days to 24 and 20 h, respectively. The stimulating effect was observed within the range of glucose concentration of 0.5-2.0 g/l in the medium. Ascorbic acid at a concentration of 10-70 mg/l as a nongrowth substrate also increased the decomposition of 2,4-dichlorophenol, though at a lower degree than glucose. Experiments with washed cells showed the limiting stage of chlorophenol degradation by R. erythropolis 1CP to be, possibly, aromatic ring dechlorination after its hydroxylation. As an additional source of electrons, glucose introduced into suspensions of washed cells grown on 3-hydroxybenzoate made it possible to eliminate the bottleneck in 2,4-dichlorophenol metabolism by significantly accelerating dechlorination of 3,5-dichlorocatechol. Based on the experimental and literature data, the enzyme systems involved in 2,4-dichlorophenol degradation by the culture R. erythropolis 1CP are assumed to be nonspecific.

Biodegradation, Environmental↗
PubMed1975

Nonsink dissolution rate equations.

In spite of the fact that film theory is based on severe assumptionss, it is shown to be a good working model. The Niebergall-Goyan equation, the Short-Sharkey-Rhodes equation, and the Pothisiri-Carstensen equation-all based on simple film theory-are shown to hold through 80-90% of the dissolutin process for p-hydroxybenzoic acid and sodium chloride, both at values below and above the amount necessary to saturate the dissolution medium. Deviations are attributed to experimental difficulties and to improper definition of monodisperseness rather than to the assumptions made in the theory.

Chemistry, Pharmaceutical↗
PubMed1977

Effect of sorbitol on interaction of phenolic preservatives with polysorbate 80.

The effect of sorbital on the binding of several commonly used phenolic preservatives (i.e., p-hydroxybenzoic acid, methylparaben, ethylparaben, and propylparaben) with the nonionic surfactant polysorbate 80 was investigated using an equilibrium dialysis technique. The binding data were expressed in the form of Scatchard plots utilizing a modified form of the Scatchard equation. The data analysis indicated that all four phenolic preservatives were bound to two distinct loci within the polysorbate micelle; one exhibited a high affinity and a low capacity for the preservative molecules, while the other appeared to have a near-zero affinity but an almost infinite binding capacity. The high affinity site was assumed to be located near the junction of the hydrocarbon core with the polyoxyethylene region of the micelle. The interaction of the preservatives with the second class of sites apparently involved a non-specific and nonsaturable partitioning of the preservative molecules into the polyoxyethylene region of the micelle. Sorbitol was ineffective in displacing significant amounts of bound preservative from either binding site, presumably because it was too polar to partition into the micelle sufficiently to displace bound preservative.

Chemical Phenomena↗
PubMed2005

Selective extraction of derivates of p-hydroxy-benzoic acid from plant material by using a molecularly imprinted polymer.

Selective SPE of derivates of p-hydroxybenzoic acid (pHBA) from plant extract of Melissa officinalis is presented using a molecularly imprinted polymer (MIP) made with protocatechuic acid (PA) as template molecule. MIP was prepared with acrylamide as functional monomer, ethylene glycol dimethacrylate as crosslinking monomer and ACN as porogen. MIP was evaluated towards six phenolic acids: PA, gallic acid, pHBA, vanillic acid (VA), gentisic acid (GeA) and syringic acid (SyrA), and then steps of molecularly imprinted SPE (MISPE) procedure were optimized. The best specific binding capacity of MIP was obtained for PA in ACN (34.7 microg/g of MIP). Other tested acids were also bound on MIP if they were dissolved in this solvent. ACN was chosen as solvent for sample application. M. officinalis was extracted into methanol/water (4:1, v/v), the extract was then evaporated to dryness and dissolved in ACN before application on MIP. Water and ACN were used as washing solvents and elution of benzoic acids was performed by means of a mixture methanol/acetic acid (9:1, v/v). pHBA, GA, PA and VA were extracted with recoveries of 56.3-82.1% using this MISPE method. GeA was not determined in plant extract.

Acetic Acid↗
PubMedDate not supplied

A germacranolide and three hydroxybenzyl alcohol derivatives from Hieracium murorum and Crepis bocconi.

The methanol extract of sub-aerial parts of Hieracium murorum L. gave germacra-7 alpha H-1(10)E,4Z,11 (13)-trien-12,8 alpha-olide-15-oic acid (15-->1)-beta-D-glucopyranosyl ester (1), a new sesquiterpenoid of the germacrane-type, and two new 4-hydroxybenzyl alcohol derivatives, 4-hydroxy-cinnamomic acid 4-beta-D-glucopyranosyloxybenzyl ester (2) and 3-hydroxy-2-[(4-hydroxy-phenyl)-acetoxy]-3-methyl-butyric 4-beta-D-glucopyranosyloxybenzyl ester (3). The methanol extract of sub-aerial parts of Crepis bocconi P. D. Sell gave 4-hydroxybenzoic acid 4-beta-D-glucopyranosyloxybenzyl ester (4), another new 4-hydroxybenzyl alcohol derivative. The structures of these compounds were established by means of MS and one- and two dimensional-NMR experiments.

Asteraceae↗
PubMed1997

Identification of a novel conserved sequence motif in flavoprotein hydroxylases with a putative dual function in FAD/NAD(P)H binding.

A novel conserved sequence motif has been located among the flavoprotein hydroxylases. Based on the crystal structure and site-directed mutagenesis studies of p-hydroxybenzoate hydroxylase (PHBH) from Pseudomonas fluorescens, this amino acid fingerprint sequence is proposed to play a dual function in both FAD and NAD(P)H binding. In PHBH, the novel sequence motif (residues 153-166) includes strand A4 and the N-terminal part of helix H7. The conserved amino acids Asp 159, Gly 160, and Arg 166 are necessary for maintaining the structure. The backbone oxygen of Cys 158 and backbone nitrogens of Gly 160 and Phe 161 interact indirectly with the pyrophosphate moiety of FAD, whereas it is known from mutagenesis studies that the side chain of the moderately conserved His 162 is involved in NADPH binding.

4-Hydroxybenzoate-3-Monooxygenase↗
PubMed2004

Characterization of phenolic acids in black carrots (Daucus carota ssp. sativus var. atrorubens Alef.) by high-performance liquid chromatography/electrospray ionization mass spectrometry.

Phenolic acids were extracted from black carrot roots (Daucus carota ssp. sativus var. atrorubens Alef.) and a black carrot juice concentrate, and characterized by high-performance liquid chromatography/electrospray ionization mass spectrometry. Most of the compounds detected were identified as depsides composed of p-coumaric, caffeic and ferulic acids. Additionally, three hydroxybenzoic acid derivatives and one quercetin glycoside were detected. 5-O-Caffeoylquinic acid (chlorogenic acid) represented the predominant compound amounting to 657 mg/kg in the roots and 5815 mg/kg in the concentrate. The specific fragmentation patterns of mono- and dihydroxycinnamoylquinic acids allowed the distinction of several stereoisomers. The presence of 4-O-caffeoylquinic acid and several further hydroxycinnamic acid esters, together with compounds not belonging to the depside type, is reported for the first time. The present study reveals that the phenolic profile of black carrots is even more complex than hitherto assumed and may contribute to pigment stability of extracts derived from the roots.

Beverages↗
PubMed2002

An in vitro hydroxyl radical generation assay for microdialysis sampling calibration.

A xanthine oxidase hydroxyl radical (.OH)-generating system was created for sustained in vitro production of *OH. This assay was coupled with microdialysis sampling to elucidate the factors that influence microdialysis calibration during radical trapping. A *OH trapping agent, 4-hydroxybenzoic acid, was included either in the microdialysis perfusion fluid or in the medium external to the microdialysis probe. Xanthine oxidase enzymatic activity was reproducible and had an average activity measured by UV absorbance of produced uric acid of 0.037 +/- 0.005 deltaAU/min (n = 5). A considerable amount of variance in the rate and amount of the product, 3,4-dihydroxybenzoic acid (3,4-DHBA), was observed when one microdialysis probe was placed in the reaction mixture. When two microdialysis probes were placed in the reaction mixture, a greater rate and amount of 3,4-DHBA was observed. Different concentrations of 3,4-DHBA were obtained between quiescent and stirred systems.

Ascorbic Acid↗
PubMed2000

Molecular cloning and functional characterization of a novel nuclear receptor similar to an embryonic benzoate receptor BXR.

Benzoate X receptor (BXR) is a member of the nuclear hormone receptor superfamily and is activated by alkyl esters of amino benzoic acids and expressed during early development stages. We report here a second BXR, which was cloned by screening Xenopus laevis embryonic cDNA libraries. This new BXR, termed BXRbeta, exhibits 97% identity in the DNA-binding domain and 79% identity in the ligand-binding domain in amino acid sequence to previously reported Xenopus BXR. The BXRbeta strongly binds as a heterodimer with retinoid X receptor (RXR) to direct repeats of an AGGTCA motif spaced 4 or 5 base pairs apart and activates transcription by addition of methyprednisolone and dexamethasone as well as amino- and hydroxybenzoates.

Amino Acid Sequence↗
PubMed2005

Benzoate hydroxylation: a measure of oxidative stress in divers.

Hyperoxia may facilitate the formation of reactive oxygen species. Recent experiments indicated signs of oxidative stress after 3.5 h hyperoxic diving. We analyzed in the urine of healthy, 100% O2-breathing male volunteers before and after 45 min seawater diving (170 kPa) or 30 min resting at 280 kPa in a pressure chamber (HBO) for sub-fractions of hydroxybenzoate (HB), monohydroxybenzoate (MHB), and of dihydroxybenzoate (DHB). Measurements were performed by HPLC and electrochemical or UV-detection. Additionally, urinary concentrations of thiobarbituric acid-reactive substances (TBARS) and of creatinine (CREA) were analyzed by standard colorimetric assays. During HBO treatment, TBARS, DHB, 2,4-DHB, and 3,4-DHB increased significantly. MHB and CREA did not change. 2,4- and 3,4-DHB-alterations correlated with changes in TBARS. Diving induced urine dilution and stimulated oxygen consumption. Urinary TBARS and HB rose significantly higher during diving at 170 kPa than during HBO at 280 kPa. A different pattern in urinary sub-fractions of DHB could be observed in divers: 2,6 > 2,3 > 2,5 > 3,4. Changes in 2,6- and 2,5-DHB correlated significantly with alterations in TBARS. 2,6-DHB probably indicated renal oxidant stress similar to previously described animal experiments. It is concluded that analyzing urinary HB may provide a sensitive measure to quantify and qualify oxidant stress in divers.

Adult↗