Related Aromatic Compounds Research Articles

Bisphenol A and Dental Sealants: Olea's Response.

Comments on "Determination of bisphenol A and related aromatic compounds released from Bis-GMA-based composites and sealants by high performance liquid chromatography." by ulgar R, Olea-Serrano MF, Novillo-Fertrell A, Rivas A, Pazos P, Pedraza V, Navajas J-M, Olea N. Environ Health Perspect 108:21-27 (2000).

Bisphenol A and Dental Sealants: Olea's Response

Comments on "Determination of bisphenol A and related aromatic compounds released from Bis-GMA-based composites and sealants by high performance liquid chromatography." by ulgar R, Olea-Serrano MF, Novillo-Fertrell A, Rivas A, Pazos P, Pedraza V, Navajas J-M, Olea N. Environ Health Perspect 108:21-27 (2000).

Phenylacetyl-coenzyme A is the true inducer of the phenylacetic acid catabolism pathway in Pseudomonas putida U.

Aerobic degradation of phenylacetic acid in Pseudomonas putida U is carried out by a central catabolism pathway (phenylacetyl-coenzyme A [CoA] catabolon core). Induction of this route was analyzed by using different mutants specifically designed for this objective. Our results revealed that the true inducer molecule is phenylacetyl-CoA and not other structurally or catabolically related aromatic compounds.

Azo dye-mediated regulation of total phenolics and peroxidase activity in thyme (Thymus vulgaris L.) and rosemary (Rosmarinus officinalis L.) clonal lines.

Thyme (Thymus vulgaris L.) and rosemary (Rosmarinus officinalis L.) clonal lines, which were previously isolated from a heterogeneous seed population by plant tissue culture techniques, have been targeted as potential plants for phytoremediation of organic pollutants such as azo dyes and related aromatic compounds. Three thyme clonal lines and three rosemary clonal lines were tested for the ability to grow on hormone-free medium containing 0.01% of azo dye Poly S-119. The results showed that dye tolerance was associated with reduced phenolics and enhanced peroxidase activity in these clonal lines. There was a clear inverse correlation between total phenolics and peroxidase activity in these plants in response to Poly S-119. The tolerance of these clonal lines showed variations at different growing stages. These observations suggested that the peroxidase activity was inducible. Because peroxidases are involved in lignification, wound healing, aromatic compound degradation, pathogen defense, and stiffening, the results suggest that azo dye stimulated the defense response of thyme and rosemary clonal plants by increasing the peroxidase activity. Stereomicroscopic observations revealed that the azo dye was sequestered within the growing axis of the plant roots, which may also enhance the polymerization of azo dye onto the cell wall with the help of enhanced peroxidase activity.

Determination of bisphenol A and related aromatic compounds released from bis-GMA-based composites and sealants by high performance liquid chromatography.

Most of the composites and sealants used in dentistry are based on bisphenol A diglycidylether methacrylate (Bis-GMA). Reports revealed that in situ polymerization is not complete and that free monomers can be detected by different analytic methods. Concerns about the estrogenicity of bisphenol A (BPA) and other aromatic components leached from commercial products have been expressed. We studied biphenolic components eluted from seven composites and one sealant before and after in vitro polymerization using HPLC and gas chromatography/mass spectrometry and we investigated how pH modifications affect the leaching of these components. We found BPA (maximal amount 1.8 microg/mg dental material), its dimethacrylate derivative (Bis-DMA, 1.15 microg/mg), bisphenol A diglycidylether (6. 1 microg/mg), Bis-GMA (2.0 microg/mg), and ethoxylate and propoxylate of bisphenol A in media in which samples of different commercial products were maintained under controlled pH and temperature conditions. Our results confirm the leaching of estrogenic monomers into the environment by Bis-GMA-based composites and sealants in concentrations at which biologic effects have been demonstrated in in vivo experimental models. The main issue with implications for patient care and dentist responsibility is to further determine the clinical relevance of this estrogenic exposure.

Identification of Polymeric Dye-Tolerant Oregano (Origanum vulgare) Clonal Lines by Quantifying Total Phenolics and Peroxidase Activity

High phenolic-containing oregano clonal lines have been targeted as potential plants for developing pollutant-tolerant rhizospheres that could accelerate microbial degradation of pollutants such as polymeric dyes and related aromatic compounds. Seven tissue culture-generated oregano clonal lines were found to grow on hormone-free medium containing 0.01% of Poly R-478 or Poly S-119. The results showed that dye tolerance was associated with changes in total phenolics and peroxidase activity in these clonal lines. The total phenolics of most clonal lines decreased in response to polymeric dyes, whereas the peroxidase activity increased. Clonal line O-5 pretreated with Pseudomonas exhibited a higher level of peroxidase activity compared to untreated O-5 in response to the dyes. These observations suggested that the peroxidase activity was inducible. Stereomicroscopic observations revealed that the polymeric dyes were sequestered within the growing axis of the roots. This process may also enhance the polymeriz...

In situ gene expression in mixed-culture biofilms: evidence of metabolic interactions between community members.

Microbial communities growing in laboratory-based flow chambers were investigated in order to study compartmentalization of specific gene expression. Among the community members studied, the focus was in particular on Pseudomonas putida and a strain of an Acinetobacter sp., and the genes studied are involved in the biodegradation of toluene and related aromatic compounds. The upper-pathway promoter (Pu) and the meta-pathway promoter (Pm) from the TOL plasmid were fused independently to the gene coding for the green fluorescent protein (GFP), and expression from these promoters was studied in P. putida, which was a dominant community member. Biofilms were cultured in flow chambers, which in combination with scanning confocal laser microscopy allowed direct monitoring of promoter activity with single-cell spatial resolution. Expression from the Pu promoter was homogeneously induced by benzyl alcohol in both community and pure-culture biofilms, while the Pm promoter was induced in the mixed community but not in a pure-culture biofilm. By sequentially adding community members, induction of Pm was shown to be a consequence of direct metabolic interactions between an Acinetobacter species and P. putida. Furthermore, in fixed biofilm samples organism identity was determined and gene expression was visualized at the same time by combining GFP expression with in situ hybridization with fluorescence-labeled 16S rRNA targeting probes. This combination of techniques is a powerful approach for investigating structure-function relationships in microbial communities.

Metabolism and toxicity of diisopropylnaphthalene as compared to naphthalene and monoalkyl naphthalenes: a minireview

Detailed knowledge does exist on the toxicological safety of diisopropylnaphthalene (DIPN). Its metabolism is the key to understanding its very low toxicity. The metabolic pathway of 2,6-DIPN in rats was found to proceed almost exclusively through oxidation of the isopropyl side-chain. This has decisive toxicological implications, which could be demonstrated by comparing the lung-specific toxic effects of naphthalenes in mouse: the lack of ring oxidation correlates well with lack of lung toxicity while, vice versa, the extent of enzymatic oxidative attack at the aromatic ring structure results in a toxic pattern that is observed with naphthalene and its monomethyl derivatives. It is concluded that DIPN and other highly alkylated naphthalenes are supposed to offer favourable safety properties because of their `alkyl character' and therefore must not be compared with the toxic properties of naphthalene and closely related aromatic compounds.

Determination of hydroxyl radicals using salicylate as a trapping agent by gas chromatography-mass spectrometry

Objectives: To establish a sensitive method for measuring hydroxyl radical formation in biological systems using salicylate as probe. Methods: Salicylate hydroxylation products and related aromatic compounds were extracted and converted to trimethylsilyl (TMS) derivatives. The derivatives were analyzed by gas chromatography-mass spectrometry (GC-MS). Quantitation was achieved by selected-ion-recording (SIR) with benzoic acid (ring-D5) as an internal standard. Results: All compounds were well separated and specifically quantitated by a GC-MS procedure. Standard curves were linear in the concentration ranges investigated (0.1–10 nmol) for all individual compounds. Recovery from human plasma was in the range of 90–102%. The detection limit was between 50 fmol–1 pmol per 1 μL injection. The within-run and between-run coefficients of variation were between 4.6–9.1%. We were able to detect the baseline levels of hydroxylation products in human fibroblasts after incubation with salicylate. Conclusions: The GC-MS assay presented here can specifically identify and quantitate salicylate hydroxylation products and related aromatic compounds, which can be used as an in vivo marker of oxidative stress. This sensitive method has broad applications, both in the area of free radical medicine and in the pharmacological study of aspirin and its metabolites.

Pentamidine congeners. 4. DNA binding affinity and anti- Pneumocystis carinii activity of butamidine analogues

A number of pentamidine-like compounds are known to bind to DNA. DNA could therefore be the molecular target for the anti- P. carinii activity of these compounds. We provide the first evidence demonstrating a correlation between in vitro anti- P. carinii activity and in vitro DNA binding affinity of pentamidine related aromatic dicationic compounds.

Sweden - Peroxidase biosensor for monitoring phenol and related aromatic compounds: In ANAL. CHIM. ACTA (311/3 (245–253) 1995) T. Ruzgas, J. Emneus, L. Gorton & G. Marko-Varga of the University of Lund report on ‘The development of a peroxidase biosensor for monitoring phenol and related aromatic compounds’

Sweden - Peroxidase biosensor for monitoring phenol and related aromatic compounds: In ANAL. CHIM. ACTA (311/3 (245–253) 1995) T. Ruzgas, J. Emneus, L. Gorton & G. Marko-Varga of the University of Lund report on ‘The development of a peroxidase biosensor for monitoring phenol and related aromatic compounds’

Direct regulation of the ATPase activity of the transcriptional activator DmpR by aromatic compounds

The NtrC-like regulator DmpR controls transcription from the dmp operon that encodes the enzymes for catabolism of phenol and some related aromatic compounds. DmpR activates transcription from the sigma 54-dependent dmp-operon promoter in the presence of pathway substrates or structural analogues in the growth medium. Using affinity-purified DmpR and a truncated derivative, we show here that aromatic compounds directly activate the ATPase activity of this protein in vitro, and that the amino-terminal domain represses this activity in the absence of an aromatic ligand. In order to dissect the activation process, derivatives of DmpR exhibiting single amino acid changes were isolated and their effector-dependence and specificity profiles were analysed in vivo. The mechanistic implications of the phenotypes of these mutants are discussed.

The development of a peroxidase biosensor for monitoring phenol and related aromatic compounds

The possibility of horseradish peroxidase (HRP) modified solid graphite and carbon paste electrodes to perform as biosensors for the determination of phenol and related compounds was studied. Phenoxy radicals, formed during the enzymatic oxidation of phenolic compounds in the presence of hydrogen peroxide, are reduced electrochemically. The reduction current is proportional to their concentration in the solution. From the hydrodynamic voltammograms, calibration curves and performance stability it was concluded that the reduction of phenoxy radicals is more efficient at the solid graphite electrodes in comparison with the carbon paste based sensor. The potentials, at which electrochemical reduction of phenoxy radicals appears, depend on the electron donating properties of the substituent in the phenol molecule. It was found that, in the presence of 10–20 μM of H 2O 2 in the solution, the responses of HRP-modified solid graphite electrode to p-cresol are rate limited by the enzymatic reaction. The electrode was most stable when the buffer solution contained 5% of methanol. Among 20 phenolic compounds tested, phenol, catechol, resorcinol, p-cresol, 4-chlorophenol, 2,4-dichlorophenol, 4-chloro-3-methylphenol, vanillin and 2-amino-4-chlorophenol can be determined. The greatest sensitivity was obtained for 2-amino-4-chlorophenol (85 nA cm −2 μM −1).

Anaerobic oxidation of toluene (analogues) to benzoate (analogues) by whole cells and by cell extracts of a denitrifying Thauera sp.

Toluene and related aromatic compounds can be mineralized to CO2 under anoxic conditions. Oxidation requires new dehydrogenase-type enzymes and water as oxygen source, as opposed to the aerobic enzymatic attack by oxygenases, which depends on molecular oxygen. We studied the anaerobic process in the denitrifying bacterium Thauera sp. strain K172. Toluene and a number of its fluoro-, chloro- and methyl-analogues were transformed to benzoate and the respective analogues by whole cells and by cell extracts. The transformation of xylene isomers to methylbenzoate isomers suggests that xylene degradation is similarly initiated by oxidation of one of the methyl groups. Toluene oxidation was strongly, but reversibly inhibited by benzyl alcohol. The in vitro oxidation of the methyl group was coupled to the reduction of nitrate, required glycerol for activity, and was inhibited by oxygen. Cells also contained benzyl alcohol dehydrogenase (NAD+), benzaldehyde dehydrogenase (NADP+), benzoate-CoA ligase (AMP-forming), and benzoyl-CoA reductase (dearomatizing). The toluene-oxidizing activity was induced when cells were grown anaerobically with toluene and also with benzyl alcohol or benzaldehyde, suggesting that benzyl alcohol or benzaldehyde acts as inducer. The other enzymes were similarly active in cells grown with toluene, benzyl alcohol, benzaldehyde, or benzoate. This is the first in vitro study of anaerobic oxidation of an aromatic hydrocarbon and of the whole-cell regulation of the toluene-oxidizing enzyme.

Antiproliferative activity to vascular smooth muscle cells and receptor binding of heparin-mimicking polyaromatic anionic compounds.

Proliferation of bovine aortic smooth muscle cells (SMCs) induced by thrombin, basic fibroblast growth factor, or serum is inhibited by anionic, nonsulfated aromatic compounds that mimic many of the effects of heparin. Among these compounds are aurintricarboxylic acid (ATA) and a newly synthesized polymer of 4-hydroxyphenoxy acetic acid (compound RG-13577). Iodinated- or 14C-labeled compound RG-13577 binds to cultured SMCs in a highly specific and saturable manner. Scatchard analysis of the binding data revealed the presence of an estimated 1 x 10(7) binding sites per cell with an apparent dissociation constant of 3 x 10(-6) mol/L. Binding of radiolabeled RG-13577 was efficiently competed for by related aromatic anionic compounds and by apolipoprotein E, but not by heparin, heparan sulfate, suramin, or various purified growth factors and extracellular matrix proteins. Receptor cross-linking of SMC-bound 125I-RG-13577 revealed a single species of high M(r) (approximately 280 kD) cell surface receptors detected in the absence but not the presence of excess unlabeled compound RG-13577. Binding was susceptible to downregulation and restoration of receptor levels in a manner similar to that of hormone and growth factor receptors. We suggest that the antiproliferative activity of compound RG-13577 and related compounds is initiated by binding to specific growth-inhibiting cell surface receptors. Heparin-mimicking compounds may be applied to inhibit SMC proliferation associated with atherosclerosis and restenosis.

Qualitative and quantitative carbohydrate analysis of fermentation substrates and broths by liquid chromatographic techniques

Quantitative and qualitative aspects of the column liquid chromatographic analysis of carbohydrates in complex fermentation media are considered. Two fermentations of lignocellulose hydrolysates with Saccharomyces cerevisiae for the production of fuel ethanol were followed. In one spent sulphite liquor and in another an enzymatic hydrolysate of Salix caprea was used as the fermentation substrate. Two of the most commonly used chromatographic set-ups, one ligand-exchange and one ion-exchange system with refractive index and pulsed amperometric detection, respectively, were used to determine the carbohydrates. Some interfering compounds were eliminated by solid-phase extraction prior to sample introduction into the separation system. However, incomplete clean-up of the samples before chromatographic separation resulted in co-elution of matrix compounds with the sugars, introducing quantitative and qualitative errors in the evaluation of the sugar content. In fact, only in 30% of the samples analysed did the results between the two methods agree within 5%. The carbohydrate content of the fermentation samples as given by the two chromatographic methods is presented. Liquid chromatography coupled with thermospray mass spectrometry in both positive- and negative-ion modes was used for the characterization of the molecular ions of glucose, xylose, galactose, arabinose, mannose and well known interfering compounds such as phenolics and related aromatic compounds, and applied to biotechnological fermentation samples for qualitative analysis. Diode-array UV spectrophotometry was used as a complementary detection technique in order to identify unequivocally carbohydrates present in these fermentation media and trace interfering phenolic compounds.

Degradation of Lignin Monomers by the Hindgut Flora of Xylophagous Termites

Summary The hindgut flora of the lower termites Mastotermes darwiniensis (Froggatt) and Reticulitermes santonensis (Feytaud) and the higher termite Nasutitermes nigriceps (Haldeman) was tested for its in vivo and in vitro capability to degrade lignin monomers and related aromatic compounds. From the three termites, 53 bacteria were isolated in liquid and on solid media, containing aromatic compounds as carbon source. Most of the tested aromatic compounds were degraded aerobically by mixed and pure cultures. Under fermentative conditions the aromatic compounds were only partially degraded and the aromatic ring was not split. The results suggest that in the anaerobic hindgut the breakdown of aromatic ring systems requires oxygen, which is most probably supplied via the aerated paunch epithelium.

Cyclodextrin-modified micellar electrokinetic chromatography: Separation of hydrophobic and enantiomeric compounds

Cyclodextrin (CD)-modified micellar electrokinetic chromatography was applied to the separation of closely related aromatic compounds and enantiomeric separations using CD together with sodium dodecyl sulphate (SDS). Nine isomeric dimethylnaphthalenes, which were not resolved at all with an SDS solution, were successfully separated with γ-CD and SDS. Sixteen polycyclic aromatic hydrocarbons were also almost completely separated. Dansylated (DnS)- dl-amino acids were optically resolved with combinations of SDS and β- or γ-CD and sodium taurodeoxycholate and γ-CD. Maltoheptaose was employed instead of CD, giving partial resolution of some DnS- dl-amino acids.

Mechanism of the reaction of methylene with benzene: a study of kinetic hydrogen isotope effects and theoretical calculations

The reaction mechanism of singlet and triplet methylene with benzene and related aromatic compounds was investigated by kinetic isotope effects (KIEs), solvents effects, and product studies. The results are further rationalized by a series of ab initio calculations at MP2/6-31G * //RHF/6-31G * and UMP2/6-31G * //UHF/6-31G * levels of theory. The proposed 1c intermediate for the triplet reaction was found by means of the calculations, whereas no singlet analog 1 could be found

The methanogenic degradation of m-cresol and related aromatic compounds

The methanogenic degradation of m-cresol and related aromatic compounds