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PubMed2006

Charge migration in dicationic electrophiles and its application to the synthesis of aza-polycyclic aromatic compounds.

[reaction: see text] Superacid-promoted reactions of dicationic electrophiles have been studied, and the positive charge centers are found to migrate apart in a predictable manner. Using isotopic labeling the charge migration is found in one system to occur through successive deprotonation-reprotonation steps. The charge migration chemistry is the basis for new general synthetic route to aza-polycyclic aromatic compounds.

Aza Compounds↗

PubMed2004

Flavonoids and aromatic compounds from the rhizomes of Zingiber zerumbet.

Repeated column chromatography of the CHCl3-soluble fraction of Zingiber zerumbet led to the isolation and identification of two aromatic compounds, p-hydroxybenzaldehyde (1) and vanillin (2), and six kaempferol derivatives, kaempferol-3,4',7-O-trimethylether (3), kaempferol-3-O-methylether (4), kaempferol-3,4'-O-dimethylether (5), 4''-O-acetylafzelin (6), kaempferol-3-O-(4-O-acetyl-alpha-L-rhamnopyranoside)], 2'',4''-O-diacetylafzelin (7), kaempferol-3-O-(2,4-O-diacetyl-alpha-L-rhamnopyranoside)], and 3'',4''-O-diacetylafzelin (8), kaempferol-3-O-(3,4-O-diacetyl-alpha-L-rhamnopyranoside)]. The structures of 1-8 were identified by analysis of spectroscopic data as well as by comparison with published values. This is the first report on the isolation of compounds 1-3 from this plant.

Benzaldehydes↗

PubMed2003

Kinetic model for the sonochemical degradation of monocyclic aromatic compounds in aqueous solution: new insights.

The kinetic model of De Visscher et al. [J. Phys. Chem. 100 (1996) 11636] for the sonochemical degradation of apolar monocyclic aromatic compounds in aqueous solution is based on a large number of assumptions, some of which have never been stated explicitly. An example is a homogeneous temperature of cavitation. The present study focuses on those "hidden assumptions", and reveals that some of them are not realistic. It is shown that an entirely different set of assumptions leads to essentially the same mathematical formulation of the kinetics. The old and new version of the model can be considered as limiting cases which envelope the real conditions of ultrasonic cavitation chemistry. However, the new model does not lead to the inconsistencies experienced with the old model.

Journal Article↗

PubMedDate not supplied

Kohonen network study of aromatic compounds based on electronic and nonelectronic structure descriptors.

Atoms in Molecules (AIM) and Electron Localization Function (ELF) methodologies were applied to describe the electronic structure of 88 aromatic compounds. The analyzed database contains molecules substituted by nucleophilic and electrophilic groups which are responsible for electron density distribution in the molecule and further for its reactivity. Radial Distribution Function (RDF), Weighted Holistic Invariant Molecular (WHIM), Three-Dimensional Molecule Representation of Structures based on Electron Diffraction (3D-MoRSE) and Geometry, Topology and Atom-Weights Assembly (GETAWAY) descriptors were taken into account describing the structures of the analyzed molecules. According to generated descriptor space the classification of the molecules has been subsequently performed using unsupervised learning strategy and Kohonen network. The final step of descriptor space testing was supervised learning of Counter-Propagation Artificial Neural Network (CPANN) using n-octanol/water partition coefficient (logP), dipole moment (DM) and molecular refractivity (MR) as target values.

Journal Article↗

PubMed1990

Immune responses in BALB/c mice following immunization with aromatic compound or purine-dependent Salmonella typhimurium strains.

Two near isogenic strains of Salmonella typhimurium HWSH, stably mutated in either the aroA gene affecting the biosynthesis of aromatic compounds, or the purA gene affecting the biosynthesis of purines, were administered intravenously as live attenuated vaccines to BALB/c mice. HWSH aroA-immunized mice were well protected against intravenous (i.v.) challenge with wild-type virulent HWSH for at least 10 weeks, whereas HWSH purA-immunized mice were unprotected. Furthermore, HWSH aroA-immunized mice could also control a heterologous challenge with virulent Listeria monocytogenes at 7 and 14 days post-immunization, whereas mice receiving a similar dose of HWSH purA could not. Increasing the i.v. dose of HWSH purA compared to HWSH aroA induced some resistance to L. monocytogenes. Induction of early anti-S. typhimurium resistance by HWSH aroA immunization appeared slightly later than the anti-L. monocytogenes resistance. Mice immunized with either vaccine were able to mount S. typhimurium-specific T-cell proliferative responses and produced anti-S. typhimurium humoral antibodies in their serum. The antibody titre was greater in those mice immunized with the aroA mutant.

Animals↗

PubMedDate not supplied

[Assessment of exposure to organic aromatic compounds and PAH in asphalt industry: the PPTP-POPA Study results].

Asphalt is a mixture of mineral matter and bitumen, its fumes contain about 1% of Polycyclic Aromatic Hydrocarbons (PAH), some of which are carcinogens. In the PPTP-POPA Study of Lombardy Region, a group of 100 asphalt workers (exposed to bitumen fumes and diesel exhausts) and a group of 47 ground construction operators (exposed only to diesel exhausts) were investigated to assess PAH exposure in Italy, by means of environmental-air monitoring (the 16 most relevant, according to the American Environmental Protection Agency, EPA) and biological monitoring (urinary 1-hydroxypyrene excretion). Our results show that PAH exposure in these workers is not higher than that observed in traffic policemen working in urban areas. Since dermal exposure has been suggested as a major determinant of the total PAH dose absorbed by road pavers from bitumen fumes, we assessed skin contamination by organic aromatic compounds and by sixteen PAH: in both groups, six pads were applied to each subject in different parts of the body, during the workshift. The results show that the dermal contamination in road pavers is higher than in ground construction operators and that cutaneous dose rate is higher than respiratory dose rate, whereas the amount of absorption the ratio is inverted.

Adult↗

PubMed1993

Biodegradation of chlorinated aliphatics and aromatic compounds in total-recycle expanded-bed biofilm reactors.

Ground-water contamination by chlorinated aliphatic compounds is a major cause for concern because of their toxicity. This study examined the biodegradation of trichloroethylene and aromatic compounds by microbial consortia enriched from contaminated subsurface sediments. The consortia were capable of utilizing methane and propane as sources of carbon and energy. Two continuously recycled expanded-bed bioreactors were inoculated with (1) the subsurface consortium, and (2) P. fluorescence, P. putida (strains pRB1401 and pWWO), and M. trichosporium OB3b. An uninoculated reactor containing 0.2% sodium azide and 0.5% formalin served as the control. Methane (5% v/v) and propane (3% v/v) were maintained by batch feeding through the course of the experiment. Greater than 97% degradation of trichloroethylene was observed over a period of 12 d. More than 99% of benzene, toluene, and xylene were degraded within the first 7 d. Dissolved oxygen levels were measured and found to be in the range 4.9-6.5 mg/L throughout the experiments.

Benzene↗

PubMedDate not supplied

Behavior of aromatic compounds contained in kraft mill effluents treated by an aerated lagoon.

Kraft mill effluents were biologically treated in an aerated lagoon (AL) (3.4 L) to evaluate the behavior of aromatic compounds by UV-vis spectroscopy. Under aerobic conditions, biological oxygen demand (BOD(5)) removal was between 84% and 95%, whereas soluble chemical oxygen demand (COD(s)) removal ranged between 40% and 60%. A slight increase was observed in the VIS(436)/COD(s) relationship (0.101-0.110), indicating that color reduction was less than the total organic matter reduction expressed by COD(s). Additionally, low values of UV(254)/UV(280) (1.23-1.12) indicate the presence of lignin-derived compounds in the aerobic effluent relationship. Ultrafiltration (UF) analysis shows that color was concentrated in the molecular weight fraction larger than 10,000 Da. The recalcitrant fraction was found to be resistant to further biodegradation, even under optimized microbiological conditions.

Bacteria, Aerobic↗

PubMed2002

Biomonitoring of polycyclic aromatic compounds in the urine of mining workers occupationally exposed to diesel exhaust.

Diesel exhaust is considered a probable human carcinogen by the IARC. Biomonitoring of workers occupationally exposed to diesel exhaust was performed to determine their internal burden of diesel associated aromatic compounds. Personal air sampling also allowed to determine the exposure of the miners at their work place towards several polycyclic aromatic hydrocarbons (PAH) and nitro-arenes, the latter of which are thought to be specific constituents of diesel exhaust. For biomonitoring the urine of 18 underground salt miners was collected during and after their shift for 24-hours. half of the 18 miners were smokers. The urinary levels of 1-hydroxypyrene and hydroxylated phenanthrene metabolites were determined as biomarkers of PAH exposure, whereas urinary levels of some aromatic amines were chosen to monitor exposure towards specific nitro-arenes from diesel exhaust like 1-nitropyrene and 3-nitrobenzanthrone and to monitor the human burden by these compounds from inhaled cigarette smoke. Non-smoking workers exposed to diesel exhaust excrete an average level of about 4 micrograms phenanthrene metabolites, whereas the urinary levels in smokers were up to 3-fold higher. In summary the results indicate that (i) diesel exposure led to an increase of PAH metabolism in the workers examined, most probably by an induction of cytochrome P450 (ii) smokers could be identified in accordance with earlier studies by their increased ratio of phenanthrene metabolites derived from 1,2- and 3,4-oxidation and their higher amounts of excreted 1-naphthylamine, and (iii) the excreted amounts of aromatic amines found as metabolites of the nitro-arenes were about 5- to 10-fold higher as one might expect from the levels determined by personal air sampling at the workplace of the individuals.

Biomarkers↗

PubMed2001

Development of quantitative structure-activity relationships for the toxicity of aromatic compounds to Tetrahymena pyriformis: comparative assessment of the methodologies.

The purpose of this study was to develop quantitative structure-activity relationships (QSARs) for the toxicity of 268 aromatic compounds in the Tetrahymena pyriformis growth inhibition assay. The QSARs were developed using the response-surface (or two-parameter) approach, which was also modified using linear free-energy parameters to account for outliers. Subsequently, the data set was analyzed using partial least-squares (PLS). The results of the modeling using different methodologies were compared to the use of a Bayesian regularized neural network (BRANN) trained on the same data. Both response surface approaches, and PLS explained between 75 and 80% of the variance in the data; BRANN gave a higher statistical fit. In terms of the transparency of the approaches, the response surface clearly provides the simplest and easiest to use QSAR, it is readily interpreted in terms of mechanism of toxic action. PLS and BRANN are respectively less transparent. The use of atomistic and fragment-based indexes as descriptors in QSARs is assessed also, these are found not to be as useful as whole molecule parameters for the prediction of toxicity for molecules outside of the training set. The relative merits of the different approaches to the development of QSARs are described.

Animals↗

PubMed1988

Determination of polynuclear aromatic compounds in composted municipal refuse and compost-amended soils by a simple clean-up procedure.

A rapid and reproducible procedure suitable for the analysis of polycyclic aromatic compounds (PACs) in sludges and soil samples has been developed. The PACs are isolated by ultrasonic extraction with methyl chloride, redissolution of the crude extract in isooctane and clean-up of the PAC-containing fraction by chromatography on alumina micro-columns. After separation and quantitative determination of the various PACs by capillary gas chromatography/mass spectrometry, more than 50 PAC compounds which cover a wide range of concentrations were detected in the sludge samples. The most abundant compounds were mono-, di- and trimethyl derivatives of naphthalene, phenanthrene, fluorene, dibenzethiophene and naphthothiophene. No accumulation of PAC in an agricultural soil after an experiment of compost application over three years was observed.

Fatty Acids↗

PubMed1982

Interaction of povidone with aromatic compounds III: Thermodynamics of the binding equilibria and interaction forces in buffer solutions at varying pH values and varying dielectric constant.

The complex formation of a series of aromatic compounds with povidone was studied in buffer solutions and organic solvent mixtures by equilibrium dialysis. For all the ligand molecules studied, a linear relationship was found between r, the number of moles of bound ligand per mole of povidone, and the free ligand concentration. The binding constants and the free energies of binding (-delta F), were greater for compounds in the nonionic state and increased with the number of hydroxyl groups which were capable of forming hydrogen bonds. They decreased with temperature elevation. The thermodynamic data showed entropy gains during the binding process accompanied by small negative enthalpy values. The increased ability to form hydrogen bonds and the increase in ionization of the ligand molecule was reflected in more negative delta H and decreasing delta S values. (The thermodynamic values were interpreted on the basis of the "iceberg" concept of water structure.) From these entropy and enthalpy changes, hydrogen and hydrophobic bondings appeared to be the most important types of binding. In organic solvent mixtures, the association constants lowered with increasing ethanol or propylene glycol concentration; a line relationship between the free energy and the dielectric constant of the solvent mixtures was observed.

Buffers↗

PubMed2005

Assessment of baseline toxicity of mono-cyclic aromatic compounds by pseudomonas initial oxygen uptake assay.

The objective of this study was to develop quantitative structure-activity relationships (QSARs) for the toxicity of mono-cyclic aromatic compounds in the Pseudomonas putida initial oxygen uptake assay. The QSARs were developed using response-surface based on descriptors for chemical hydrophobicity (logP) and electrophilicity (LUMO). The model log (Ki(-1)=0.434 (+/-0.011) log P-0.389 (+/-0.013) LUMO - 2.13(+/-0.031); n=155, r2=0.941, r2(adj)=0.940, s=0.119, F=1206 led us to conclude that the polar and non-polar narcotics were statistically indistinguishable. Pentafluorophenol, pentachlorophenol and most dinitrophenols classified as weak acid respiratory uncouplers in literature fit well into this model when they were treated as their corresponding phenoxides. This latter result suggests that the action mechanism of these phenols should be reevaluated.

1-Octanol↗

PubMed2006

Effects and uptake of polycyclic aromatic compounds in snails (Helix aspersa).

The International Standardization Organization recently launched a soil toxicity test with snails (Helix aspersa). We assessed the sensitivity of this test for seven polycyclic aromatic compounds. Control animals had 100% survival and low variability for growth measurements. Maximum exposure concentrations of 2800 mg/kg (4000 mg/kg for acridine) had no effect on survival. Similarly, growth (biomass and shell size) was not affected by pyrene, fluoranthene, fluorene, carbazole, phenanthrene, or acridine, whereas dibenzothiophene gave a 10% effect concentration of 1600 mg/kg. Measured internal concentrations of carbazole, dibenzothiophene, and acridine increased with increasing soil concentrations, but biota-soil accumulation factors were low (0.002-0.1). Compared to previously tested organisms, with all being exposed in the same soil type and under similar test conditions, the H. aspersa test was relatively insensitive to all substances.

Animals↗

PubMed2004

Selective detection of volatile aromatic compounds using a compact laser ionization detector with fast gas chromatography.

We report results for a new gas chromatography detector that is comparatively sensitive and far more selective for aromatic compounds than the traditional photoionization detector. The detection means is multiphoton ionization at atmospheric pressure. The ionization source in these experiments is a diode-pumped passively Q-switched microchip laser operating at 266 nm. Experiments were conducted with the detector interfaced to a fast gas chromatograph. For <20 s elution time, limits of detection were <1 pg for toluene, ethylbenzene, xylenes, and isopropylbenzene; the limit of detection for benzene is approximately 10 pg. Detector response was linear over 5 orders of magnitude, including these low levels. Negligible signals were observed for nonaromatic ketones, aldehydes, ethers, and cycloalkanes at levels as high as 0.1 microg (10 mg/L concentration). Detector efficiency after fast GC separation was 0.002% when using a detector cell with a radius of 1.1 cm and a purge gas flow of 500 mL/min. The advantages of this detector are further illustrated by the fast GC analysis of fuel samples.

Journal Article↗

PubMed1998

Biotransformation of nitroso aromatic compounds and 2-oxo acids to N-hydroxy-N-arylacylamides by thiamine-dependent enzymes in rat liver.

The formation of N-hydroxy-N-arylacylamides from nitroso aromatic compounds and 2-oxo acids was investigated using rat liver subcellular fractions. Activities were found in both mitochondria and cytosol, except for activities for phenylpyruvate and glyoxylate; the former did not produce N-hydroxy-N-phenylphenylacetamide and the latter nonenzymatically produced N-hydroxy-N-phenylformamide with nitrosobenzene (NOB). The cytosolic activity of N-hydroxy-N-phenylglycolamide formation was indicated to be due to transketolase, which utilized hydroxypyruvate as a glycolic aldehyde donor to NOB. With mitochondria, 2-oxo acids (including hydroxypyruvate) served as substrates for the biotransformation of NOB to the corresponding N-hydroxy-N-phenylacylamides. The substrate preference was 2-oxobutyrate > pyruvate > 2-oxoisovalerate > 2-oxoisocaproate > 2-oxovalerate > 2-oxo-3-methylvalerate, judging from Vmax/half-saturating concentration for mitochondria values. The half-saturating concentrations for NOB were nearly constant. The mitochondrial activity was due to pyruvate dehydrogenase complex and branched-chain 2-oxo acid dehydrogenase complex (BCDHC). By using partially purified BCDHC, pyruvate and 2-oxobutyrate were found to be common substrates for both of the enzymes, and 2-oxoisovalerate was shown to be the most effective substrate for BCDHC. Analysis by the Taft equation indicated that the polar effects, rather than the steric effects, of the alkyl groups of 2-oxo acids are important for BCDHC-catalyzed formation of N-hydroxy-N-phenylacylamides. A positive Hammett constant obtained for the formation of N-hydroxy-N-arylisobutyramides indicates that an electron-withdrawing substituent makes the nitroso compounds susceptible to BCDHC-catalyzed biotransformation.

Animals↗

PubMed2004

Screening of halogenated aromatic compounds in some raw material lots for an aluminium recycling plant.

Four samples of scrap raw materials for an aluminium recycling plant were screened for the occurrence of persistent halogenated aromatic compounds. The samples contained waste from handling of electric and electronic plastics, filter dust from electronic crusher, cyclone dust from electronic crusher and light fluff from car shredder. In our screening analyses, brominated flame retardants were observed in all samples. Polybrominated diphenyl ethers (PBDE) were identified in all samples in amounts of 245-67450 ng/g. The major PBDE congeners found were decabromo- and pentabromodiphenyl ethers. 1,1-bis(2,4,6-tribromophenoxy)ethane, hexabromobenzene, ethyl-pentabromobenzene, tetrabromobisphenol-A, pentabromotoluene and dimethyl tetrabromobenzene were observed in all scrap samples. The concentrations of PCBs, PCNs (polychlorinated naphthalenes) and nona- to undecachlorinated terphenyls in some of these scrap samples were remarkably high.

Aluminum↗

PubMed1995

Easy and inexpensive diffusion tests for detecting the assimilation of aromatic compounds by yeast-like fungi. Part I. Assimilation of dihydroxyphenols.

A number of easy and inexpensive diffusion tests have been proposed to find microorganisms that are able to decompose aromatic compounds. These tests made it possible to show the assimilation of catechol, resorcinol and hydroquinone by selected yeast-like fungi. The tests may be used to choose highly active strains from culture collections.

Candida↗