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PubMed1986

The cytosolic receptor binding affinities and AHH induction potencies of 29 polynuclear aromatic hydrocarbons.

The dose-response rat hepatic cytosolic receptor-binding avidities, aryl hydrocarbon hydroxylase (AHH) and ethoxyresorufin O-deethylase (EROD) induction potencies in rat hepatoma H-4-II E cells in culture were determined for 29 polynuclear aromatic hydrocarbons. It was apparent that the magnitude of the EC50 values for these in vitro responses were strongly dependent on structure. Dibenz[a,h]anthracene (1.6 X 10(-8) M), 7-methylbenz[a]anthracene (1.6 X 10(-8) M), 3-methylcholanthrene (2.8 X 10(-8) M) and picene (4.5 X 10(-8) m) exhibited the highest affinity for the receptor protein and these compounds were only 5-fold less active the 2,3,7,8-tetrachlorodibenzo-p-dioxin (1 X 10(-8) M). All of the compounds which were active in the receptor-binding and monooxygenase enzyme-induction assays possessed one common structural feature, namely the presence of a phenanthrene structure fused with at least 1 benzo ring. The results also demonstrated that there was not any apparent correlation between the receptor-binding avidities and in vitro monooxygenase enzyme-induction potencies for the most active polynuclear aromatic hydrocarbons.

Animals↗
PubMed2000

Determination of basic nitrogen-containing polynuclear aromatic hydrocarbons formed during thermal degradation of polymers by high-performance liquid chromatography-fluorescence detection.

A method for the simultaneous determination of 22 nitrogen-containing polynuclear aromatic hydrocarbons (PAHs) (15 azaarenes and seven amino-PAHs) in the gaseous products of the thermal degradation of polymers is described. After desorption and clean-up using cation-exchange chromatography (PRS cartridge) the samples were analyzed by HPLC-FD. The validation was carried out with real nylon 6 combustion samples. The recoveries of the compounds are in the range of 89-99% for the extraction and 91-100% for the clean up procedure. The detection limits ranged from 7 to 160 pg. The high recovery values, due to the quick and efficient clean-up procedure, resulted in low relative standard deviations (with the exception of acridine and 2-aminoanthracene <5%). The applicability of the method is also investigated for the determination of the N-PAHs in a pyrolysis sample.

Chromatography, High Pressure Liquid↗
PubMed1972

Water pollution: organic compounds in the Charles River, Boston.

The major lipophilic organic compounds present in water collected during November and December 1971 from the Charles River Basin (Boston) are as follows: normal alkanes (C(15) to C(31)), alkyl naphthalenes, alkyl anthracenes or phenanthrenes, pyrene, fluoranthene, dibutyl phthalate, and di(2-ethylhexyl) phthalate. The concentration of the naphthalenes (determined by liquid chromatography) correlates with the effective storm-water runoff content of the river. These data suggest a multiplicity of sources ranging from indigenous biological materials to automobile exhaust condensate.

Alkanes↗
PubMed2005

Diels-alder adducts of 3,6-dibromophencyclone with symmetrical 1,4-disubstituted-cis-2-butenes: comparisons with the adduct of phencyclone and N-benzylmaleimide, and one-dimensional and two-dimensional nuclear magnetic resonance studies and ab initio structure calculations.

Hindered Diels-Alder adducts have been prepared from 3,6-dibromophencyclone, 2, with cis-1,4-diacetoxy-2-butene, 3; cis-2-butene-1,4-diol, 4; and N-benzylmaleimide, 5. The adduct from the parent phencyclone, 1, with N-benzylmaleimide was prepared for comparison. One- and two-dimensional (1D and 2D) proton and carbon-13 NMR studies (at 7.05 tesla, ambient temperatures), including high-resolution COSY45 and HETCOR (XHCORR) chemical shift correlation spectra, were performed, allowing extensive rigorous assignments for protons and protonated carbons. Substantial anisotropic shielding was seen for the ortho protons of the N-benzyl group in the adducts of 5 with 1 or 2, with these aryl protons resonating at 6.25 ppm (CDCl3) for each adduct. The unsubstituted bridgehead phenyls of all four adducts showed slow exchange limit (SEL) 1H and 13C spectra. Greater shift dispersions for the bridge-head phenyl protons in the adducts from 5 relative to those from 3 or 4 suggested the role of the imide carbonyls for anisotropic contributions or for influences on adduct geometry. Ab initio geometry optimizations were performed at the Hartree-Fock level with the 6-31G* basis set (or the LACVP* basis set for the bromine-containing compounds) for each of the adducts. For the two adducts from benzylmaleimide, separate minima were located corresponding to conformers in which the benzyl group was directed into the adduct cavity (syn) or out of the adduct cavity (anti). Calculated energies and geometric parameters for the adducts are presented, and these suggested a significantly different structure for the dibromo diacetate adduct, in terms of general symmetry and bridgehead phenyl geometries, compared to the other adducts.

Alkenes↗
PubMed2007

Cyclostreptin binds covalently to microtubule pores and lumenal taxoid binding sites.

Cyclostreptin (1), a natural product from Streptomyces sp. 9885, irreversibly stabilizes cellular microtubules, causes cell cycle arrest, evades drug resistance mediated by P-glycoprotein in a tumor cell line and potently inhibits paclitaxel binding to microtubules, yet it only weakly induces tubulin assembly. In trying to understand this paradox, we observed irreversible binding of synthetic cyclostreptin to tubulin. This results from formation of covalent crosslinks to beta-tubulin in cellular microtubules and microtubules formed from purified tubulin in a 1:1 total stoichiometry distributed between Thr220 (at the outer surface of a pore in the microtubule wall) and Asn228 (at the lumenal paclitaxel site). Unpolymerized tubulin was only labeled at Thr220. Thus, the pore region of beta-tubulin is an undescribed binding site that (i) elucidates the mechanism by which taxoid-site compounds reach the kinetically unfavorable lumenal site and (ii) explains how taxoid-site drugs induce microtubule formation from dimeric and oligomeric tubulin.

Alkanes↗
PubMed2001

Luminescence spectroscopy as a screening tool for the potential carcinogenicity of asphalt fumes.

A subset of polycyclic aromatic compounds (PACs), which contain 4-6 annulated rings, has been documented as the source of carcinogenicity in animal skin painting studies of petroleum products and asphalt fumes (M. L. Machado, P. W. Beatty, J. C. Fetzer, A. H. Glickman and E. L. McGinnis, Fundam. Appl. Toxicol., 1993, 21, 492; T. A. Roy, S. W. Johnson, G. R. Blackburn and C. R. Mackerer, Fundam. Appl. Toxicol., 1988, 10, 466). Because of the chemical complexity of these materials, it has been difficult to identify the specific compounds within this broad range of PACs responsible for their carcinogenicity. An alternative approach using luminescence spectroscopy was taken in this study to quantify, without identification, a subset of these compounds that appears to cause cancer. The fluorescence response at a specific wavelength pair was obtained for 39 laboratory asphalt fume condensates from animal skin painting studies, yielding a linear correlation coefficient of R2 = 0.96 between the fluorescence response in these materials and the carcinogenicity found in animal studies. In the absence of other asphalt fume condensates from animal studies, 17 petroleum oils were also evaluated using this method and compared with the available animal skin painting data. The details of the method include a clean-up step that removes the highly polar compounds and spectral subtraction of two- and three-ring PAC interference, both of which add to the fluorescence response, yet were not found to contribute to a carcinogenic response from skin painting studies. Full scan fluorescence plots also produce a fingerprint which can be used to assess contamination, such as coal tar products or mixtures of materials, that are not defined as asphalt, yet may be present in the working environment.

Air Pollutants↗
PubMed1983

Tumor promoters and cocarcinogens in tobacco carcinogenesis.

Cigarette smoke induces carcinoma of the larynx in Syrian golden hamsters and is active as a tumor promoter in hamsters pretreated with a low dose of a PAH, nitrosamine, or nitrosamide. These tumorigenic effects are only observed with total smoke, but not with the gas phase alone. This demonstrates that the tumorigenic agents reside primarily in the particulate phase. According to fractionation experiments, a number of four- and five-ring aromatic hydrocarbons serve as the major tumor initiators in tobacco smoke. Tumor promoters reside primarily in weakly polaric neutral subfractions and in the weakly acidic portion of the particulate matter and include certain unsaturated hydrocarbons and phenolic compounds. Cocarcinogenic activity is a characteristic feature of tobacco smoke and its particulates. Among the cocarcinogens formed during combustion are catechols and certain nontumorigenic aromatic hydrocarbons and terpenes. Nicotine may also serve as a cocarcinogen as is indicated by preliminary data. The action of tumor promoters and cocarcinogens in tobacco carcinogenesis, the precursors for tobacco smoke promoters and cocarcinogens, and methods for their reduction in smoke are discussed.

9,10-Dimethyl-1,2-benzanthracene↗
PubMedDate not supplied

[The tobacco-cancer problem].

Statistical, biological and chemical data on the carcinogenic effect of tobacco smoke are given and are discussed. The epidemiological studies have clearly shown the particularly noxious action of inhalation, and the direct ratio between the risk and the number of cigarettes smoked. The laboratory experiments on biological properties of cigarette smoke raise various problems of interpretation, however they reinforce the results given by statistical studies on man. The quantities of carcinogenic compounds which have been isolated from cigarette smoke are too small to account for the whole action. The co-carcinogenic, promoting, necrosing and toxic effects of some smoke condensate fractions could play an important part in the carcinogenic action. To cope with the health problems of the smoking habit, the tobaccoproducers and the public health organisations have taken steps, which led to a better knowledge of the problem and to the production of cigarettes which are less harmful to man.

Animals↗
PubMed1999

Levels of dioxin-like compounds in sewage sludge determined with a bioassay based on EROD induction in chicken embryo liver cultures.

A bioassay for the detection of dioxin-like compounds was used to estimate levels in sewage sludge from Swedish sewage treatment plants (STPs). The sludge extracts were HPLC-separated into three fractions containing a) monoaromatic/aliphatic, b) diaromatic (e.g. polychlorinated biphenyls [PCBs], polychlorinated dibenzodioxins and polychlorinated dibenzofurans [PCDDs/Fs]), and c) polyaromatic compounds (e.g. polycyclic aromatic hydrocarbons [PAHs]). The bioassay, which is based on EROD (7-ethoxyresorufin O-deethylase) induction in cultured chicken embryo livers detected dioxin-like activity in all unfractionated extracts and in the di- and polyaromatic fractions of all sludge extracts, but not in the monoaromatic/aliphatic fractions. The levels ranged between 6 and 109 pg bio-TEQ/g sludge (d.w.). In sediment samples from rural lakes in Sweden, levels of about 5 pg bio-TEQ/g (d.w.) have been found. The polyaromatic fractions of the sludge samples were potent in the bioassay, probably due to various PAHs and other polyaromatics in the sludge. The levels of six PAHs that are screened for in the sludge at Swedish STPs accounted for only 3-10% of the observed EROD-induction by the polyaromatic fractions. Consequently, many other polyaromatic EROD-inducing compounds were present in the sludge. Inclusion of a biological test like the chicken embryo liver bioassay in the screening of sludge would improve the ability to detect the presence of bioactive dioxin-like compounds. A theoretical estimation of bio-TEQ concentrations in farm-soil following long-term application of sludge with bio-TEQ concentrations similar to those observed in this investigation indicated that the bio-TEQ levels in soil would increase very slowly over time. The chicken embryo liver bioassay proved useful in assessing levels of dioxin-like compounds in sewage sludge and it gives valuable complementary information to chemical analysis data.

Animals↗
PubMed2003

Photochemical access to tetra- and pentacyclic terpene-like products from R-(+)-sclareolide.

Fused tetracyclic oxetanes 4, highly substituted cyclobutenes 6, and the pentacyclic derivatives 7 and 8 were obtained by irradiation of derivatives 3 that were prepared from commercial R-(+)-sclareolide (1) in three steps. Compounds 4 are formed through a Paterno-Büchi reaction, while tricyclic derivatives 6 are the fragmentation products of the first formed oxetanes. In clear contrast, cyclopentenyl and 3-furyl derivatives, 3e and 3f, gave the [2+2] adducts, namely pentacyclic derivatives 7 and 8. All the reported reactions are totally regio- and stereoselective, with the exception of the cyclization of furyl derivative 3f, which gave the mixture of both the crossed (7b) and the right (8) isomers.

Diterpenes↗
PubMed1976

Metabolic studies and the evaluation of genetic risk from the viewpoint of industrial toxicology.

In recent years some important industrial chemicals, e.g. solvents, and monomers used in the production of plastics, have been found to be more dangerous than had been suspected. Some of them are mutagens and carcinogens. The active substance may be the compound itself, but more frequently it is a reactive intermediate, an alkylating agent, formed from the parent compound by oxidation under the influence of liver-microsome mixed-function oxidases. Trichloroethylene, vinyl chloride, 1,1-dichloroethylene and 2-chloro-1,3-butadiene can be mentioned as examples, where mutagenic or carcinogenic activity has been demonstrated; similar activity of some others is to be suspected. Metabolic studies may explain unexpected effects or they may allow one to predict such effects. Tests on microorganisms with a metabolic activation in vitro seem to be extremely valuable for fast and efficient screening of man-made chemicals to be introduced into the environment, because such tests combine the use of liver microsomes and bacteria for detection and classification of the effect. Mutagenicity tests in mammals do not lose their usefulness, since thay take into account the distribution of the compound in the body, its transport to the target organ, species-specific differences etc. As exposures of workers to chemicals mentioned above have been quantitatively measured regularly, epidemiological studies should be performed with regard to mutagenic and carcinogenic effects in relation to the degree of exposure. Here is a chance for better understanding of how to extrapolate experimental results to human populations and how to establish safe levels of chemicals in the environment if at all possible and acceptable.

Alkenes↗
PubMed2002

An experimental set up of a PAH vapour generator and its use to test an annular denuder.

The aim of this work is to develop and test a dynamic gas generator for semi-volatile organic compounds (SVOC). A single compound, naphthalene, is used as a surrogate PAH to test the system. The dynamic generation of PAH is based on the permeation technique [Analyst 106 (1981) 817; Am. Ind. Hyg. Assoc. J. 38 (1977) 712]. Monitoring the temperature and measuring the mass of PAH present in the permeation chamber every 48 h gives a direct measurement of the sublimation rate of the PAH. Knowing the flow rate, gives an accurate value of the concentration of PAH from the generator. It was found stable over a period of time under constant operating conditions. This concentration is diluted down to between 0.3 and 30 ppbv by a controlled flow of pure air. The diluting airflow is a mixture of dry and wet air, making it possible to control the relative humidity of the flow from the generator as well as its concentration in PAH. We used this generator to calibrate an annular denuder tube, based on the study by Gundel et al. [Atmos. Environ. 29 (1995) 1719]. Although this technique has been shown to be artefact-free for sampling gaseous PAH [Polycyclic Aromatic Compounds 9 (1996) 67; Atmos. Environ. 28 (1994) 3083], its trapping efficiency still depends on environmental parameters (temperature, relative humidity and sampling duration). Accordingly, we used our generator to calibrate a single annular denuder under controlled conditions (T degrees C, HR%, CPAH, sampling duration). The trapping efficiency of the denuder was calculated by two independent methods. Firstly, by comparing the amount trapped on a denuder with the measured mass sublimated in the generator. Secondly, by putting two denuders in series and comparing the mass collected on the first and the second tube. These two methods gave similar results, within the 10% relative uncertainties of both methods. The first results obtained show that, in environmental conditions, the efficiency ranges between 90 and 100%.

Environmental Monitoring↗
PubMed2002

Deferred standards, an on-line qualification, validation and system stability probe for chromatographic assay.

Specific programming of automated HPLC systems allows total on-line qualification, validation and stability monitoring using the concept of deferred standards. Setting up such a process for routine analyses in an automated HPLC system requires specific autosampler programming as well as specific monitoring software. With an autosampler, a double injection procedure is programmed, the first introducing the sample, and the second, a few minutes deferred, the deferred control standard. Two additional compounds are therefore added to the sample before and during the chromatographic process: the intemal standard for sample quantification and the deferred standard for system control. Specific methodologies are described of how to obtain classical quantitative analysis information as well as system qualification validation stability information. Experiments were performed to develop specified methodologies to monitor the quality of quantitative analysis during the life of the column by using the deferred standard concept to probe the effects of column ageing on separation characteristics.

Automation↗
PubMed2003

The Pauson-Khand reaction, a powerful synthetic tool for the synthesis of complex molecules.

There are still some synthetic chemists who hesitate to use metal-mediated or -catalysed reactions. The Pauson-Khand reaction (PKR) is a powerful transformation that has now been sufficiently well developed to be routinely considered when planning a synthesis, especially of polycyclic complex molecules. This tutorial review aims to encourage the use of this process explaining the best ways of performing a PKR both in the stoichiometric and the catalytic version, showing the scope of the process and its limitations. Additionally, asymmetry can be introduced in the reaction using several strategies, which will be discussed. The most recent examples of the synthetic applications of the PKR in natural product synthesis will give the reader an idea of the great usefulness of this reaction.

Bridged Bicyclo Compounds↗
PubMed2000

Selective detection of nitrated polycyclic aromatic hydrocarbons by electrospray ionization mass spectrometry and constant neutral loss scanning.

The development of a method for selective detection of nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) among other polycyclic aromatic compounds (PACs) is described. The method is based on electrospray ionization mass spectrometry (ESI-MS), performed with a triple quadrupole analyzer and constant neutral loss (CNL) scanning. When subjected to ESI conditions, nitro-PAHs give rise to M(-), [M - H](-) and [M - H + 16](-) ions, which in turn produce fragments by losing 30 u, most probably NO. Other PACs do not undergo such fragmentations, and these differences can be exploited for selective detection of nitro-PAHs among other PACs. Nitro-PAHs can therefore be monitored through the loss of 30 u occurring under negative ion mode ESI conditions. Toward the full development of a screening method for nitro-PAHs, this article first discusses some general aspects of the negative ion mode full-scan ESI mass spectra obtained for these compounds and other PAH derivatives. Because the extent of observation of the loss of 30 u is sensitive to the ESI conditions used, the effects of ionization parameters such as solvent used, declustering voltage, and solvent flow rate are evaluated and discussed. Setting these parameters is very important, especially when interfacing a high performance liquid chromatography (HPLC) system with the ESI source of a triple quadrupole mass spectrometer. Preliminary results of on-line microbore HPLC/ESI-MS separations of PAC standards are presented, and elution/ionization conditions discussed.

Anthracenes↗
PubMed1979

Survey of some market basket commodities for polynuclear aromatic hydrocarbon content.

The Food and Drug Administration multi-component regulatory procedure for determining polynuclear aromatic hydrocarbons in foods was recently used to survey 24 foodstuffs for the presence of these compounds. The procedure has a reliable limit of quantitation of 2 ppb. The potent carcinogen benzo(a)pyrene was detected in only one of the 24 products analyzed, at a level of 3 ppb. Pyrene and/or fluoranthene were found in 19 of the 24 samples examined, at levels ranging from less than 1 ppb to about 75 ppb. A comparison of the recent survey data to that obtained approximately 10 years ago reveals that the types and levels of polynuclear aromatic hydrocarbons found are essentially unchanged.

Chromatography, Thin Layer↗
PubMed1983

Induction of specific monooxygenases by isosteric heterocyclic compounds of benz[a]anthracene, benzo[c]phenanthrene and chrysene.

Benzo[c]phenanthrene and a series of heterocyclic compounds (benzo[b]naphtho(1,2-d)thiophene; benzo[b]naphtho(2,1-d)thiophene; benz[a]acridine and benz[c]acridine) were tested to their capacity of inducing monooxygenase activity in rat liver by means of recording the metabolite profile of benz[a]anthracene formed in rat liver microsomal incubations. Although all compounds tested were found to be weak monooxygenase inducers the pretreatment of rats with them resulted in significant changes of the microsomal metabolite profile of benz[a]anthracene. The thiophenes equally gave rise to oxidation at the 5,6- and the 8,9-positions, whereas the benzacridines being isosteric to benz[a]anthracene favoured the K-region oxidation (5,6-oxidation). A structure-dependent effect of monooxygenase inducers on the metabolite profile of benz[a]anthracene is discussed.

Animals↗
PubMedDate not supplied

Extraction and clean-up of contaminants and toxicants from food for mass spectrometric analysis--a literature review.

This report presents a review of the literature on the extraction and clean-up procedures used prior to the analysis, by mass spectrometry, of organic contaminants and toxicants in foods and food-related materials. It includes a brief description of the uses of a mass spectrometer and shows how the mode of operation of the machine can influence the amount of clean-up necessary before a sample is presented for analysis. The review covers a variety of contaminants of different compound types in a wide range of foods and not only discusses sample preparation techniques that have been used for contaminant analysis by mass spectrometry but also considers some that could be used. The most commonly used techniques involve solvent extraction followed by a clean-up using liquid-liquid partition or column chromatography or both, although a number of newer methods being evolved are moving towards the ideal of a single-step extraction and clean-up process.

Chemical Phenomena↗