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At least 145 records · Page 8Linked to original sources

PubMed2005

Metabolites in bile of fish from São Sebastião Channel, São Paulo, Brazil as biomarkers of exposure to petrogenic polycyclic aromatic compounds.

This study reports the analysis of polycyclic aromatic compound (PAC) metabolites, as biomarkers of exposure to PACs in marine environment. PAC metabolites were measured in bile samples from 14 species of demersal fish caught in the São Sebastião Channel (SSC), SE Brazilian coastline. Naphthalene (NPH) equivalents, phenanthrene (PHN) equivalents, and benzo[a]pyrene (BaP) equivalents were quantified using a reverse-phase high-performance liquid chromatography coupled with fluorescence detection method. For all samples, the means (+/-standard deviation, n=37) of concentrations obtained for NPH, PHN, and BaP equivalents were, respectively, 290,000+/-200,000 ng/g, 18,000+/-14,000 ng/g, and 970+/-1900 ng/g. These results indicate recent exposure of these fish to PACs in their environment. In addition, two species (Cyclichthys spinosus and Prionotus nudigula) of fish were analyzed in order to investigate local sources of PAC contamination in the SSC and the influence of the petroleum terminal in fish caught in remote areas. The results showed that these fish species potentially migrate along the channel, especially P. nudigula. Correlations among groups of PAC metabolites indicate the same petrogenic source for NPH and PHN equivalents and a combustion source (e.g., automobile, ships) for BaP equivalents. The ratio BaP/PHN equivalents (0.05+/-0.07, n=37) confirms the predominance of petrogenic PACs for contamination by these chemicals in this region.

Animals↗

PubMed2005

High-performance liquid chromatography of aromatic compounds with photochemical decomposition and tris(2,2'-bipyridine)ruthenium(III) chemiluminescence detection.

A novel high-performance liquid chromatographic method for the determination of aromatic compounds based on the on-line photochemical degradation and subsequent tris(2,2'-bipyridine)ruthenium(III) chemiluminescence detection has been developed. Chemiluminescence intensity depended upon the number of aromatic rings, UV irradiation time, and variety of substituted functional groups. One of the decomposition products of aromatic compounds by UV irradiation was identified as oxalic acid. As one application of this methodology, determination of catechins in tea has been shown. Calibration graphs, based on standard (-)-epicatechin and (-)-epigallocatechin gallate solutions, were linear over the range of 0.1-50 microM. The detection limits (signal-to-noise ratio=3) were 0.8 pmol for (-)-epigallocatechin gallate and 1.2 pmol for (-)-epicatechin. The high-performance liquid chromatography-chemiluminescence (HPLC-CL) detection method with a post-column photochemical reactor can be applied to the sensitive and selective determination of catechins in tea.

2,2'-Dipyridyl↗

PubMedDate not supplied

[Effect of aromatic compounds and Mn2+ on the ligninolytic enzyme complex from the fungus Pleurotus floridae (FRIES) Kummer--a white-rot wood fungus].

The influence of aromatic compounds and Mn ions on activities of ligninolityc enzymes from white-rot fungus Pleurotus floridae has been studied. The specific inducers: vanillic acid and vanillyl alcohol--for activity of manganese-dependent peroxidase; vanillyl alcohol--for activity of cellobiose: quinone oxidoreductase during submerged, fermentation of Pleurotus floridae in Kirk's medium have been revealed. The inducers of laccase activity among studied aromatic compounds have not been revealed. The influence of Mn2+ in concentration range 0.4-68.4 mM on activities of ligninolytic enzymes of submerged culture of fungus P. floridae has been studied. Concentration of Mn ions 32.4 mM was optimal for manganese-dependent peroxidase activity.

Benzyl Alcohols↗

PubMed1988

Anaerobic and aerobic metabolism of diverse aromatic compounds by the photosynthetic bacterium Rhodopseudomonas palustris.

The purple nonsulfur photosynthetic bacterium Rhodopseudomonas palustris used diverse aromatic compounds for growth under anaerobic and aerobic conditions. Many phenolic, dihydroxylated, and methoxylated aromatic acids, as well as aromatic aldehydes and hydroaromatic acids, supported growth of strain CGA001 in both the presence and absence of oxygen. Some compounds were metabolized under only aerobic or under only anaerobic conditions. Two other strains, CGC023 and CGD052, had similar anaerobic substrate utilization patterns, but CGD052 was able to use a slightly larger number of compounds for growth. These results show that R. palustris is far more versatile in terms of aromatic degradation than had been previously demonstrated. A mutant (CGA033) blocked in aerobic aromatic metabolism remained wild type with respect to anaerobic degradative abilities, indicating that separate metabolic pathways mediate aerobic and anaerobic breakdown of diverse aromatics. Another mutant (CGA047) was unable to grow anaerobically on either benzoate or 4-hydroxybenzoate, and these compounds accumulated in growth media when cells were grown on more complex aromatic compounds. This indicates that R. palustris has two major anaerobic routes for aromatic ring fission, one that passes through benzoate and one that passes through 4-hydroxybenzoate.

Aerobiosis↗

PubMed2004

Isolation and characterization of Xanthobacter polyaromaticivorans sp. nov. 127W that degrades polycyclic and heterocyclic aromatic compounds under extremely low oxygen conditions.

Two bacterial strains, 127W and T102, were isolated from anoxic crude oil tank sludge as effective degraders of dibenzothiophene (DBT), a model sulfur containing heterocyclic aromatic compound in crude oil. Strain 127W was more tolerant to oxygen limitation than T102 and was capable of degrading two- and three-ring polycyclic and heterocyclic aromatic compounds under both aerobic and low oxygen conditions. Strain 127W degraded 0.082, 0.055, and 0.064 mM of DBT, naphthalene, and anthracene, respectively, in one week with dissolved oxygen < or =0.2ppm (0.006 mM). Degradation by 127W cell-free extracts for DBT was increased by addition of sodium hydrogencarbonate under this oxygen concentration. Phylogenetic analysis of the 16S rRNA gene sequence and physiological characteristics indicate that the strains 127W and T102 belong to new species of the genus Xanthobacter and Pseudomonas stutzeri, respectively. We propose X. polyaromaticivorans sp. nov. 127W.

Biodegradation, Environmental↗

PubMed2001

Polypyrrole-coated capillary coupled to HPLC for in-tube solid-phase microextraction and analysis of aromatic compounds in aqueous samples.

In-tube solid-phase microextraction (SPME) based on a polypyrrole (PPY)-coated capillary was investigated for the extraction of aromatic compounds from aqueous solutions. The PPY-coated capillary was coupled on-line to HPLC that was programmed with an autosampler to achieve automated in-tube SPME and HPLC analysis. Three groups of aromatics, including both polar and nonpolar compounds, were examined. The results demonstrated that the PPY coating had a higher extraction efficiency than the currently used commercial capillary coatings, especially for polycyclic aromatic compounds and polar aromatics due to the increasing pi-pi interactions, interactions by polar functional groups, and hydrophobic interactions between the polymer and the analytes. In addition to the functional groups in the PPY coating, which contributed to the higher extraction efficiency and selectivity toward analytes, the coating's porous surface structure,which was revealed by electron microscopy experiments, provided a high surface area that allowed for high extraction efficiency. It was found that the extraction efficiency and selectivity could be tuned by changing the coating thickness. The preliminary study of the extraction mechanism indicated that analytes were extracted onto the PPY coating mainly by an adsorption mechanism. The method was used for the extraction and analysis of both polar and nonpolar aromatics in aqueous samples.

Journal Article↗

PubMed2001

Obligate sulfide-dependent degradation of methoxylated aromatic compounds and formation of methanethiol and dimethyl sulfide by a freshwater sediment isolate, Parasporobacterium paucivorans gen. nov., sp. nov.

Methanethiol (MT) and dimethyl sulfide (DMS) have been shown to be the dominant volatile organic sulfur compounds in freshwater sediments. Previous research demonstrated that in these habitats MT and DMS are derived mainly from the methylation of sulfide. In order to identify the microorganisms that are responsible for this type of MT and DMS formation, several sulfide-rich freshwater sediments were amended with two potential methyl group-donating compounds, syringate and 3,4,5-trimethoxybenzoate (0.5 mM). The addition of these methoxylated aromatic compounds resulted in excess accumulation of MT and DMS in all sediment slurries even though methanogenic consumption of MT and DMS occurred. From one of the sediment slurries tested, a novel anaerobic bacterium was isolated with syringate as the sole carbon source. The strain, designated Parasporobacterium paucivorans, produced MT and DMS from the methoxy groups of syringate. The hydroxylated aromatic residue (gallate) was converted to acetate and butyrate. Like Sporobacterium olearium, another methoxylated aromatic compound-degrading bacterium, the isolate is a member of the XIVa cluster of the low-GC-content Clostridiales group. However, the new isolate differs from all other known methoxylated aromatic compound-degrading bacteria because it was able to degrade syringate in significant amounts only in the presence of sulfide.

Bacteria, Anaerobic↗

PubMed2002

Relative sensitivity of three terrestrial invertebrate tests to polycyclic aromatic compounds.

In a project investigating the ecotoxicity of polycyclic aromatic compounds (PACs), we have previously reported on the sublethal toxicity of eight PACs to springtails (Folsomia fimetaria) and enchytraeids (Enchytraeus crypticus). The model substances included four polycyclic aromatic hydrocarbons (PAHs) and four N-S-O-heterocyclics. Here, new data are presented on the effects of PACs on the survival and growth of the earthworm Eisenia veneta, showing that, in general, earthworm growth was reduced at PAC concentrations above 25 mg/kg soil dry weight. The E. veneta tests were performed using the same soil type and very similar test conditions as for the F. fimetaria and E. crypticus tests, thus providing a good opportunity to compare the sensitivity of these three organisms. Species sensitivity was examined using the 50% reduction in survival (LC50 values) and no-observable-effect concentrations (NOEC values) for growth or reproduction as endpoints. The difference between the least and most sensitive species was generally much larger for LC50 values as compared to the NOEC values, suggesting a higher degree of uncertainty when extrapolating from one species to another for the LC50 data. For the NOEC data, relatively small differences in sensitivity was observed, but as a rather consistent pattern, F. fimetaria was the most sensitive and E. crypticus the least sensitive species. However, one substance (acridine) showed specific toxicity toward E. veneta, which was more sensitive than the two other species by more than one order of magnitude.

Animals↗

PubMed2003

Nonplanar aromatic compounds. 8. Synthesis, crystal structures, and aromaticity investigations of the 1,n-dioxa[n](2,7)pyrenophanes. How does bending affect the cyclic pi-electron delocalization of the pyrene system?

A series of 1,n-dioxa[n](2,7)pyrenophanes (n = 7-12) with increasingly nonplanar pyrene moieties was synthesized by a 9-10 step sequence starting from 5-hydroxyisophthalic acid. The crystal structure of each member of this series was determined crystallographically. Several spectroscopic properties were found to vary with the extent of the nonplanarity of the pyrene unit. The way in which the distortion from planarity of the pyrene system influences its pi-electron delocalization was investigated by using two quantitative descriptors of aromaticity based on geometry (HOMA) and magnetism (magnetic susceptibility and NICS). Both methods suggest that the aromaticity of the pyrene moiety is diminished only slightly upon increasing the bend angle theta from 0 degrees to 109.2 degrees.

Journal Article↗

PubMed2006

Catalytic destruction of brominated aromatic compounds studied in a catalyst microbed coupled to gas chromatography/mass spectrometry.

The capability of solid porous catalysts has been studied for the destruction or modification of halogenated aromatic compounds contaminating the pyrolysis oil of recycled plastics from electronic waste. A fast and simple experimental procedure is carried out using a micropyrolyser coupled to GC-MS in such a way that catalyst microbed was placed in the sample tube of the pyrolyser. The pyrolysis products of polycarbonate blended with a frequently applied flame retardant tetrabromobisphenol A (TBBPA) and epoxy resin containing TBBPA monomer units have been analysed, and the brominated components were compared with the thermal decomposition products of TBBPA and its diallyl ether. When TBBPA vapour passes through molecular sieve 4A a slight debromination and a partial cleavage of bisphenol A into phenols occur. Over molecular sieves of larger pore size (13X and NaY zeolite) an important decrease of TBBPA amount is observed indicating effective trapping ability of these catalysts of basic character for brominated aromatic compounds. A total chemical modification of the vapour was achieved by Al-MCM-41 catalyst that split TBBPA into bromophenols. Analogous results were obtained by carrying out similar experiments on diallyl ether of TBBPA. Moreover, it was revealed that brominated bisphenol A compounds are modified essentially the same way, either evaporated or evolved from a polycarbonate blend or produced by pyrolysis from an epoxy resin.

Catalysis↗

PubMedDate not supplied

Mutagenicity of polycyclic aromatic compounds (PAC) identified in source emissions and ambient air.

Several polycyclic aromatic compounds (PAC) including nitrated and oxygenated derivatives of polycyclic aromatic hydrocarbons (PAH) were tested for mutagenic activity in the Salmonella/microsome assay. Among the compounds tested the isomer mix of nitro-1-hydroxypyrenes showed the highest direct mutagenic response in both the Salmonella strain TA98 and TA100 (1251 revertants/micrograms and 463 revertants/micrograms, respectively). The direct-acting mutagenicity of the nitro-1-hydroxypyrene isomer mix was dependent upon reduction of the nitro function as evidenced by the decrease in activity observed with the nitroreductase-deficient and arylhydroxylamine esterifying-deficient tester strains. The oxygenated derivatives of PAH containing aldehyde or keto groups showed weak or no mutagenic responses. In most cases addition of S9 was essential for any mutagenic activity and the strain TA100 was more sensitive than the strain TA98. Within this group, 7H-dibenzo[c,g]fluoren-7-one showed the highest mutagenic effect; 7 and 22 revertants/micrograms using the strains TA98 and TA100, respectively.

Air Pollutants↗

PubMed2006

Phototoxicity of oil sands-derived polycyclic aromatic compounds to Japanese medaka (Oryzias latipes) embryos.

Alkylated polycyclic aromatic compounds (PACs), which are rich in dibenzothiophenes, are present in natural and reclaimed aquatic environments in the oil sands region of northern Alberta (Canada). An oil sands-derived PAC extract has been shown to induce signs of blue sac disease in Japanese medaka (Oryzias latipes) embryos. Information regarding exposure to and effects of oil sands PACs is available, but little of this information concerns the impact of modifying factors. The present study focuses on the effect of simulated solar radiation on oil sands-derived PAC toxicity to Japanese medaka embryos. Photomodification of the oil sands PAC extract caused reduced toxicity with an increase in the duration of ultraviolet (UV) exposure. Generally, mortality and developmental endpoints and, to a lesser extent, growth were affected by photomodification. Coexposures of the PAC mixture and UV caused slight increases in toxicity for mortality and embryonic developmental endpoints at the longest duration of UV exposure tested (16 h). Based on the modest phototoxicity of the oil sands PAC extract to Japanese medaka embryos, enhanced toxicity associated with UV irradiation may not be a concern for embryos of fish species that are common to the oil sands region. However, testing the effects of differing levels of UV irradiation on larval fish and invertebrates that may differ in their PAC bioaccumulation would improve our understanding concerning the importance of UV irradiation as a modifying factor in oil sands environmental risk assessment.

Animals↗

PubMed1999

Development and application of a high-performance liquid chromatography screening method for aromatic compounds in invertebrate tissues

Contamination of marine invertebrates by aromatic compounds (ACs) can occur from a variety of environmental sources, both natural and anthropogenic. Invertebrate species bioaccumulate ACs because they metabolize and eliminate them at a much slower rate than do vertebrates, such as fish. We have developed a high-performance liquid chromatography (HPLC) UV fluorescence screening method that measures ACs in invertebrate tissues. Screening methods have proven to be useful in response to environmental emergencies (e.g., oil spills) and in environmental monitoring because they are more rapid and less expensive than detailed analyses. This method was validated using three species of bivalves and lobster hepatopancreas and tail muscle as test samples. The AC screening method at naphthalene, phenanthrene, and benzo[a]pyrene wavelength pairs showed good correlation to GC/MS results. The method was also used successfully in response to the North Cape oil spill, off Narragansett, Rhode Island.http://link.springer-ny. com/link/service/journals/00244/bibs/37n2p220.html

Journal Article↗

PubMed2000

Laser-induced dispersed fluorescence detection of polycyclic aromatic compounds in soil extracts separated by capillary electrochromatography.

Polycyclic aromatic hydrocarbons (PAHs) and nitrogen containing aromatic compounds (NCACs) are characterized in soil extracts and laboratory standards by capillary electrochromatography (CEC) with laser-induced dispersed fluorescence (LIDF) detection using a liquid-nitrogen cooled charge-coupled device detector. The LIDF detection technique provides information on compound identity and, when coupled with the high separation efficiencies of the CEC technique, proves useful in the analysis of complex mixtures. Differences in fluorescence spectra also provide a means of identifying co-eluting compounds by using deconvolution algorithms. Detection limits range from 0.5 to 96x10(-10) M for selected PAHs and 0.9-3.7x10(-10) M for selected NCACs. Soil extracts are also injected onto the CEC column to evaluate chromatographic method performance with respect to complex samples and the ability to withstand exposure to environmental samples.

Chromatography, Micellar Electrokinetic Capillary↗

PubMed1977

Biochemistry of the bacterial catabolism of aromatic compounds in anaerobic environments.

Methods of aerobic degradation of aromatic compounds in the biosphere are well understood, but it is only relatively recently that it has been shown how some bacteria can also degrade these substrates in the absence of molecular oxygen. This occurs by photometabolism (Athiorhodaceae), nitrate respiration (Pseudomonas and Moraxella sp.) and methanogenic fermentation (a consortium) in which the benzene nucleus is first reduced and then cleaved by hydrolysis to yield aliphatic acids for cell growth. These methods may be used by microbial communities to catabolise man-made pollutants.

Anaerobiosis↗

PubMed2001

Conversion of various aromatic compounds by resting cells of Fusarium moniliforme strain MS31.

Resting cells of Fusarium moniliforme strain MS31 convert propylbenzene to 1-phenylpropanol with high regio- and stereospecificity. To elucidate the scope of substrate acceptability by the fungus, we used various aromatic compounds for the bioconversion. The fungus hydroxylated various alkylbenzenes at the benzylic position to produce optically active alcohols. Butylbenzene was converted to nonbenzylic alcohols. In all cases, the R absolute configuration of products was more abundant. Aromatic compounds with linear side chains and (1-methylethyl)benzene were converted to their corresponding alcohols with an enantiomeric excess of 94% to 100%. Further oxidation of the alcohols was detected, but it was weak.

Journal Article↗

PubMed2005

[Bayesian regularized BP neural network model for quantitative relationship between the electrochemical reduction potential and molecular structures of chlorinated aromatic compounds].

Bayesian regularized BP neural network (BRBPNN) technique was applied in QSPR model in environmental field. The BRBPNN model for quantitative relationship between the electrochemical reduction potential (ERP) and chemical structures of 87 chlorinated aromatic compounds was established. The structure descriptor pool is consisted of Cl number (Cl), molecular weight (MW) and 6 quantum chemistry parameters which are calculated by MOPAC2000 built in ChemOffice2004, including energy of the highest occupied molecular orbital (E(HOMO)), energy of the lowest occupied molecular orbital (E(LUMO)), heat of formation(HF), dipole(DIP), electronic energy(EE), core-core repulsion(CCR). The achieved optimal network structure was 6-20-1, which possessed stronger fitting and prediction capacity than that of the stepwise linear regression and with the correlation coefficients square and the mean square error for the training set and the test set as 0.999 and 0.000105, 0.965 and 0.00159 respectively. The sum of square weights between each input neuron and the hidden layer of BRBPNN(6-20-1) indicate the effect of descriptor on the electric potential declining in the order of ELUMO > EHOMO > HF> CCR > EE > DIP. The scatter diagrams show that the EE descriptors had positive effect on ERP, and ELUMO, HF, DIP had negative effects, and EHOMO and CCR showed ambiguous effects. Results show that Bayesian regularized BP neural network is of automated regularization parameter selection capability and thus may ensure the excellent generation ability and robustness. This study threw more light on the applicability of electrochemical treatment for the chlorinated aromatic compounds and the analysis on electrochemical reduction mechanism.

Bayes Theorem↗

PubMed1983

Determination of hydroxylated aromatic compounds produced via superoxide-dependent formation of hydroxyl radicals by liquid chromatography/electrochemistry.

Hydroxyl radicals may be formed in a xanthine oxidase/hypoxanthine system, where the superoxide anion radical O-.2 and H2O2 are produced. The superoxide-dependent production of the OH. radicals may be monitored by determining the amount of hydroxylated aromatic compounds formed in such a system. Liquid chromatography/electrochemistry is a powerful tool for the determination of hydroxylated aromatic compounds. A technique is presented in which aniline and phenol are hydroxylated in xanthine oxidase/hypoxanthine incubations. No sample derivatization is needed for the determinations which can be accomplished by direct injection of the incubation mixture. Detection limits for 1,2- and 1,4-hydroxylated compounds are in the picomole range.

Aniline Compounds↗