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PubMed1987

Ultraviolet spectrometric detection for gas chromatography of polynuclear aromatic compounds with repetitive spectral scans using absorbance and concurrent fluorescence measurements.

A computer-controlled ultraviolet spectrometric detection system for gas chromatography (GC) is described which acquires absorption spectra of gas-phase GC effluents at rates up to two 62-nm scans per s. Concurrent fluorescence measurements enhance the selectivity of this detection system, providing additional qualitative information. The system has been designed to preserve chromatographic resolution and is selective for aromatic compounds. This multi-mode GC detection is demonstrated through GC separations of polynuclear aromatic compounds with limits of detection ranging from 30 to 70 ng for absorbance measurements. The spectral information obtained with this detection system may be used for compound identification, enhancement of the selectivity and for resolving co-eluting GC eluites.

Chromatography, Gas↗
PubMed2005

Analysis of aromatic compounds in gasoline with flow-switching comprehensive two-dimensional gas chromatography.

A comprehensive two-dimensional gas chromatography (GC x GC) instrument has been created by coupling a flow-switching modulator and a standard gas chromatograph. The instrument was used to characterize the aromatic composition of gasoline. The high-resolution separation produced by flow-switching GC x GC allowed gasoline aromatics to be fully resolved from saturated components. The aromatic compounds were further separated into groups having the same carbon number. A standard gasoline sample was analyzed to evaluate the quantitative accuracy and precision of this technique. The data show that flow-switching GC x GC produces results that are comparable to gas chromatography-mass spectrometry (GC-MS) and thermal modulation GC x GC. The simple, low-cost, and robust nature of flow-switching GC x GC makes it an ideal technique for the routine analysis of aromatic compounds in gasoline.

Chromatography, Gas↗
PubMed2001

Microwave-assisted extraction of polycyclic aromatic compounds from coal.

Microwave-assisted extraction (MAE) of polycyclic aromatic compounds (PACs) from coal is shown to give the same pattern of compounds as Soxhlet extraction. MAE requires only 10 mL solvent and 10 min extraction time whereas Soxhlet uses 200 mL and takes 24 h. Although the yields were lower, dichloromethane (DCM) was preferred to pyridine, N-methyl-2-pyrrolidone (NMP), and NMP with CS2 because the pattern of the PACs is shown to be independent of solvent and DCM is a much more convenient solvent to work with.

Chromatography, Gas↗
PubMed1990

Degradation of halogenated aromatic compounds.

Due to their persistence, haloaromatics are compounds of environmental concern. Aerobically, bacteria degrade these compounds by mono- or dioxygenation of the aromatic ring. The common intermediate of these reactions is (halo)catechol. Halocatechol is cleaved either intradiol (ortho-cleavage) or extradiol (meta-cleavage). In contrast to ortho-cleavage, meta-cleavage of halocatechols yields toxic metabolites. Dehalogenation may occur fortuitously during oxygenation. Specific dehalogenation of aromatic compounds is performed by hydroxylases, in which the halo-substituent is replaced by a hydroxyl group. During reductive dehalogenation, haloaromatic compounds may act as electron-acceptors. Herewith, the halosubstituent is replaced by a hydrogen atom.

Bacteria↗
PubMed2005

Two new aromatic compounds from Hericium erinaceum (BULL.: FR.) PERS(1).

Two new aromatic compounds, erinacerins A (1) and B (2), were isolated from the fruiting bodies of Hericium erinaceum (BULL.: FR.) PERS. (Hericiaceae) together with a known compound, hericenone A (3). The structures of the new compounds were elucidated on the basis of their spectral data. It was found that 1 occurred as a racemate.

Antifungal Agents↗
PubMed1987

Contribution of polycyclic aromatic hydrocarbons and polar polycyclic aromatic compounds to the carcinogenic impact of flue gas condensate from coal-fired residential furnaces evaluated by implantation into the rat lung.

For identification of the substances chiefly responsible for the carcinogenic action of the emission condensate from coal-fired residential furnaces, the implantation method was used as a carcinogen-specific bioassay for comparison of the carcinogenic effect of various fractions with that of a total sample of flue gas condensate tested in 2 or 3 different doses. After implantation into the lungs of Osborne-Mendel rats, the condensate from coal-fired residential furnaces, a fraction containing polycyclic aromatic hydrocarbons (PAHs) and thiaarenes [sulfur-containing polycyclic aromatic compounds (S-PACs)] with 4-7 rings, as well as fraction containing more polar polycyclic aromatic compounds (PACs) and PAHs with higher molecular weight, induced lung carcinomas and sarcomas. According to probit analysis, the fraction containing PAHs plus S-PACs with 4-7 rings accounted for about 68.2% of the total carcinogenicity of flue gas condensate, whereas the fraction containing more polar PACs and higher PAHs accounted for about 54.6%. All other fractions, such as nonaromatic compounds and PACs with 2 and 3 rings, constituting about 70% of the weight of the total condensate, seemed not to be carcinogenic. Only 1.4% of the total carcinogenicity of the flue gas condensate was found to be attributable to the amount of benzo[a]pyrene (CAS: 50-32-8) present in the condensate (1.14 mg/g condensate). The contribution of more than 100% of both active fractions to the total carcinogenicity (68.2 and 54.6%) may suggest an interrelation of the fractions.

Air Pollutants↗
PubMed2001

Significance of MTD and other descriptors in lipophilicity models for chlorinated aromatic compounds.

The lipophilicity of chlorinated benzenes and 20 biphenyls has been modeled using the minimum topological difference method and MTD indices. The MTD descriptor has been optimized on its own or together with nCl (number of chlorine atoms per molecule), 2D- and 3D-descriptors such as van der Waals surface area and volume, solvent accessible surface area and solvent-accessible surface-bounded molecular volume, and the inter-planar angle of the substituted biphenyls. In lipophilicity models of chlorinated aromatic compounds the majority of descriptors, including MTD, contain essentially the information of nCl. MTD is a good lipophilicity descriptor of chlorinated aromatic compounds either alone or in association with other descriptors. For chlorobenzenes it gives r = 0.998, s = 0.069, F = 2281, and for the set of chlorinated biphenyls r = 0.974, s = 0.255, F = 338, a better result than gives the nCl descriptor (r = 0.967). The significance of MTD descriptor in different models is discussed. Beside nCl, the MTD index encodes ortho and para effects.

Benzene Derivatives↗
PubMed1990

Novel effect of aromatic compounds on the iron-dependent expression of the Escherichia coli K12 manganese superoxide dismutase (sodA) gene.

In Escherichia coli, the superoxide dismutase genes (sodA and sodB) sense the availability of Fe through the action of the fur locus [E. C. Niederhoffer, C. M. Naranjo, K. L. Bradley, J. A. Fee (1990) Control of Escherichia coli superoxide dismutases (sodA and sodB) genes by the ferric uptake regulation (fur) locus, J. Bacteriol. 172, 1930-1938]. Previous work from other laboratories has shown that a variety of metal chelators and of redox-active aromatic compounds can dramatically induce expression of sodA. Here we show that non-redox-active, non-metal-chelating aromatic compounds also enhance expression of a chromosomal sodA gene fusion and that these effects are strongly modulated by the Fur phenotype (Fur +/-) and by the availability of iron in the culture medium. The compounds studied were ethidium bromide, hemin, 2,2'-bipyridine, 1,10-phenantroline, 4,7-phenantroline, rhodamine B1, rhodamine 6G, and, for comparison to previous studies, Paraquat.

Ethidium↗
PubMed2001

Separation and characterization of gall bladder bile metabolites from speckled trout, Salvelinus fontinalis, exposed to individual polycyclic aromatic compounds.

Speckled trout, Salvelinus fontinalis, were orally exposed to individual polycyclic aromatic compounds (PACs) represented by benzo[a]pyrene, carbazole, chrysene, dibenzofuran, dibenzothiophene, fluorene, phenanthrene, and pyrene. Fish were sacrificed 7 d after exposure and the gall bladder removed for bile analysis. High pressure liquid chromatography (HPLC) with fluorescence (F) and ultraviolet (UV) detection was used to determine the presence of PAC derivatives in the bile without pretreatment. Glucuronide conjugates were predominant in all exposures with variable amounts (0-53%) of phenols and starting material. Identification of compounds was confirmed by selective extraction of less polar nonconjugated PACs and enzymatic hydrolysis of water-soluble material. This was followed by HPLC and/or gas chromatography-mass spectrometry (GCMS) characterization of the produced phenols. Total metabolite levels varied widely among compounds.

Animals↗
PubMed2004

Structural close-related aromatic compounds have different effects on laccase activity and on lcc gene expression in the ligninolytic fungus Trametes sp. I-62.

Nine phenolic compounds (p-coumaric acid, ferulic acid, guaiacol, syringol, p-methoxyphenol, pyrocatechol, phloroglucinol, 3,5-dihydroxybenzoic acid, and syringaldazine) were tested for their ability to increase laccase production in the ligninolytic basidiomycete Trametes sp. I-62. All these compounds resulted in increases in laccase activity, with the highest levels being detected in the presence of p-coumaric acid (273-fold) and guaiacol (73-fold). The three laccase isozyme genes in this fungus lcc1, lcc2, and lcc3 are differentially expressed in the presence of some of these aromatics with total lcc transcript levels differing markedly depending on the aromatic compound tested. Guaiacol (the best inducer of lcc gene transcription) and p-coumaric acid selectively induced expression of lcc1 and lcc2; ferulic acid induced lcc3 expression, while 3,5-dihydroxybenzoic acid had no marked effect on laccase gene transcription. The results demonstrate that close-related aromatic compounds appear to have different effects on both laccase activity levels and lcc gene expression in this basidiomycete.

Coumaric Acids↗
PubMed2002

Accumulation and elimination of 16 polycyclic aromatic compounds in the earthworm (Eisenia fetida).

Accumulation and elimination of different polycyclic aromatic compounds (PACs) were studied in earthworms (Eisenia fetida) exposed to contaminated soil from an old gasworks site. In total, 12 polycyclic aromatic hydrocarbons (PAHs), two N- and S-heterocyclic PACs, and two PAC-quinones were included in the study. Peak-shaped accumulation curves were found for many of the compounds. After 19 d of exposure, the ratio between concentrations in worm lipids and soil organic matter was 0.02 on average. The half-lives of the PACs were relatively long, between 2 and 11 d. The elimination rate constants, k2, correlated both with literature-derived octanol-water partition coefficients (Kow) for PAHs (r2 = 0.93) and the computed polarizability (r2 = 0.88) of all the compounds. The elimination rate constants of PAHs are comparable to those of PCBs found in earlier studies, and the linear regression coefficient, r2, of k2 against Kow for PAHs and PCBs together was 0.93.

Animals↗
PubMed1995

Actions of a versatile fluorene-degrading bacterial isolate on polycyclic aromatic compounds.

Pseudomonas cepacia F297 grew with fluorene as a sole source of carbon and energy; its growth yield corresponded to an assimilation of about 40% of fluorene carbon. The accumulation of a ring meta-cleavage product during growth and the identification of 1-indanone in growth media and washed-cell suspensions suggest that strain F297 metabolizes fluorene by mechanisms analogous to those of naphthalene degradation. In addition to fluorene, strain F297 utilized for growth a wide variety of polycyclic aromatic compounds (PACs), including naphthalene, 2,3-dimethylnaphthalene, phenanthrene, anthracene, and dibenzothiophene. Fluorene-induced cells of the strain also transformed 2,6-dimethylnaphthalene, biphenyl, dibenzofuran, acenaphthene, and acenaphthylene. The identification of products formed from those substrates (by gas chromatography-mass spectrometry) in washed-cell suspensions indicates that P. cepacia F297 carries out the following reactions: (i) aromatic ring oxidation and cleavage, apparently using the pyruvate released for growth, (ii) methyl group oxidations, (iii) methylenic oxidations, and (iv) S oxidations of aromatic sulfur heterocycles. Strain F297 grew with a creosote-PAC mixture, producing an almost complete removal of all aromatic compounds containing 2 to 3 rings in 14 days, as demonstrated by gas chromatography analysis of the remaining PACs recovered from cultures. The identification of key chemicals confirmed that not only are certain compounds depleted but also the anticipated reaction products are found.

Biodegradation, Environmental↗
PubMed2005

Characterization of charcoal adsorption sites for aromatic compounds: insights drawn from single-solute and bi-solute competitive experiments.

Charcoal, the residue of incomplete biomass burning that is found in many soils and sediments, is considered a high affinity sorbent for organic pollutants. However, little is known about the microscopic processes controlling sorption. The purpose of this study was to gain molecular-scale insight into the sorption on a charcoal of three weakly soluble aromatic compounds [benzene (BEN), toluene (TOL), and nitrobenzene (NBZ)] by conducting both single-solute and bi-solute experiments. The charcoal (420 m2 g(-1)) was produced from maple wood shavings by oxygen-limited pyrolysis at 673 K. Solute affinity for charcoal followed the order NBZ > TOL > BEN. Commonly employed sorption models did not adequately describe the single-solute isotherms. Competition in both TOL-BEN and the TOL-NBZ bi-solute systems was strong. Normalization of the isotherms for the hydrophobic driving force by using an existing free energy correlation between sorption and partitioning to an inert solvent (benzene or n-hexadecane) with a nonpolar aromatic compound calibration set resulted in a finding of enhanced sorption of NBZ relative to the coalesced BEN and TOL isotherms, indicating some specificity in the interaction of NBZ. The competitive data indicated 1:1 molar competition between BEN and TOL and between NBZ and TOL, showing conclusively that this specificity was not due to a subpopulation of sorption sites unique to NBZ. H-bonding was ruled out, as the relative affinity for the sorbent among the solutes did not change at all when increasing the solution pH from 6.5 to 11. 1H NMR experiments showed molecular complexation in chloroform between NBZ and model graphene polycyclic aromatic units (naphthalene, phenanthrene, and pyrene) which was absentfor BEN and TOL. This result, in combination with the results of a companion study (Zhu and Pignatello, Environ. Sci. Technol. (in press)), is used to support the existence of pi-pi electron donor-acceptor interactions between NBZ (electron acceptor) and the polycyclic aromatic charcoal surface (electron donor) as the cause of enhanced NBZ sorption.

Adsorption↗
PubMed1998

Modulation of ceramide-activated protein phosphatase 2A activity by low molecular weight aromatic compounds.

Protein phosphatase 2A (PP2A) is one of the most important and abundant serine/threonine phosphatases in mammalian tissues and plays a role in gene expression, cell division, and signal transduction. PP2A is activated by ceramide, which is produced by the hydrolysis of membrane sphingomyelin in response to a variety of stress-related stimuli. To further study the role of ceramide-mediated signal transduction in cellular processes such as senescence and apoptosis, we designed and synthesized a series of low molecular weight aromatic compounds, mainly of the isoquinolone and tetralone classes, and evaluated their ability to inhibit enzymes known to be activated by ceramide. Those enzymes studied were ceramide-activated protein kinase, protein kinase C zeta and PP2A. Of these, only PP2A was found to be inhibited. A few of the compounds inhibited both ceramide-activated as well as basal PP2A activity. In addition, several of the compounds activated PP2A by up to 300% above basal enzyme activity, but only in the presence of ceramide. Thus, modulation (both inhibition and activation) of the catatylic activity of ceramide-activated PP2A is demonstrated by certain low molecular weight aromatic compounds.

Blotting, Western↗
PubMed2001

Biotransformation of various substituted aromatic compounds to chiral dihydrodihydroxy derivatives.

The biotransformation of four different classes of aromatic compounds by the Escherichia coli strain DH5alpha(pTCB 144), which contained the chlorobenzene dioxygenase (CDO) from Pseudomonas sp. strain P51, was examined. CDO oxidized biphenyl as well as monochlorobiphenyls to the corresponding cis-2,3-dihydro-2,3-dihydroxy derivatives, whereby oxidation occurred on the unsubstituted ring. No higher substituted biphenyls were oxidized. The absolute configurations of several monosubstituted cis-benzene dihydrodiols formed by CDO were determined. All had an S configuration at the carbon atom in meta position to the substituent on the benzene nucleus. With one exception, the enantiomeric excess of several 1,4-disubstituted cis-benzene dihydrodiols formed by CDO was higher than that of the products formed by two toluene dioxygenases. Naphthalene was oxidized to enantiomerically pure (+)-cis-(1R,2S)-dihydroxy-1,2-dihydronaphthalene. All absolute configurations were identical to those of the products formed by toluene dioxygenases of Pseudomonas putida UV4 and P. putida F39/D. The formation rate of (+)-cis-(1R,2S)-dihydroxy-1,2-dihydronaphthalene was significantly higher (about 45 to 200%) than those of several monosubstituted cis-benzene dihydrodiols and more than four times higher than the formation rate of cis-benzene dihydrodiol. A new gas chromatographic method was developed to determine the enantiomeric excess of the oxidation products.

Benzene↗
PubMed1985

Toxicity of chlorinated aromatic compounds in animals and humans: in vitro approaches to toxic mechanisms and risk assessment.

Human exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and chlorinated analogs commonly results in pathological changes in the skin and its appendages characterized by thickening of the epidermis (acanthosis), hyperkeratosis and squamous metaplasia of the epithelial lining of the sebaceous glands. Acneform lesions (chloracne) develop as hair follicles dilate and fill with keratin and sebaceous glands become cystic. In animal models it has been found that the chloracneogenic potential of the halogenated aromatic compounds examined corresponds with the relative affinity of these same compounds for the cytosolic TCDD receptor. This receptor controls the coordinate expression of a number of inducible enzyme activities and in certain cell targets can alter normal programs of proliferation and differentiation. In this report we describe some of our ongoing studies on the mechanisms of action of TCDD in normal human epidermal cells and squamous cell carcinoma (SCC) lines. These systems permit detailed investigation of the molecular and biochemical events underlying pathologic changes in the skin and offer the potential of establishing a risk assessment model for halogenated aromatic compounds by using human target cells.

Animals↗
PubMed2000

Purification, partial characterization, and reactivity with aromatic compounds of two laccases from Marasmius quercophilus strain 17.

Two isozymes of laccase were obtained from an induced liquid culture of Marasmius quercophilus with p-hydroxybenzoic acid as the inducer. Both the constitutive and the induced isozyme have a molecular mass of 60 kDa as determined by polyacrylamide gel electrophoresis. Using isoelectric focusing, we found three isozymes with the constitutive enzyme (pI 4, 4.2, 4.4) and four of the induced form (pI 4.75, 4.85, 4.95, 5.1). We observed certain differences between these two isozymes; the specific activity of the induced isozyme was twice as high, and two optimum pH levels (5 and 6) were observed with the induced isozyme (only one, pH 5, for the constitutive isozyme). However, both of these enzymes have the same thermal stability and the same temperature for their highest activity (80 degrees C). Furthermore, the reactivity of both these enzymes with aromatic compounds was similar. The use of mediators extended the oxidized substrate range of the laccases studied. Various products of degradation were observed, depending on the mediator used. When laccase was used alone, the decrease of the signal corresponding to the aromatic cycle, without any formations of other peaks at different wavelengths, suggested polymerisation of aromatic compounds.

Agaricales↗