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PubMed1996

In vitro studies of the genotoxic effects of bitumen and coal-tar fume condensates: comparison of data obtained by mutagenicity testing and DNA adduct analysis by 32P-postlabelling.

Bitumens contain traces of polycyclic aromatic compounds (PACs), a part of which will end up in the fumes emitted during hot handling of bitumen-containing products, e.g. during roadpaving. Although exposure of workers to these fumes is low, it might lead to health problems. Studies on bitumen fume condensates (BFCs) showed weak to moderate mutagenic activities, but studies on DNA adduct formation have not been reported. Therefore, a study was initiated in which fumes were generated from two road grade bitumens, in such a way that they were representative of the fumes produced in the field. The combined vapour/particulates were tested in vitro for their ability to produce DNA adducts and in modified Ames mutation assays, using a number of different strains. An attempt was made to relate the results to chemical data, such as the content of a number of individual polycyclic aromatic hydrocarbons (PAHs) and with a measure for the total PAC content. As a reference material fume condensate from coal-tar (coal-tar pitch volatiles; CTPV) were subjected to the same tests. All fume condensates tested were mutagenic to all strains and induced the formation of DNA adducts. The patterns of DNA adducts, obtained by 32P-postlabelling, arising from the BFCs were qualitatively different from the patterns of adducts obtained from the CTPVs, implying qualitative differences in the nature of the compounds responsible for the formation of these adducts. This is corroborated by the observation that for BFCs quantitative adduct levels are higher than would be expected based on the PAH content. These data thus indicate that the PAHs analysed are not the sole components responsible for adduct formation from BFCs, but that an important contribution comes from other (hetero- and/or substituted-) PACs.

Animals↗
PubMed1979

Measurement of DNA-excision repair in suspensions of freshly isolated rat hepatocytes after exposure to some carcinogenic compounds: its possible use in carcinogenicity screening.

When suspensions of freshly isolated rat hepatocytes were exposed to a number of carcinogenic compounds, it was possible to measure an increased UDS by a rapid procedure via liquid-scintillation counting. For a number of carcinogenic compounds and some of their non-carcinogenic structural analogues a good correlation between the carcinogenic property and the ability to induce UDS was demonstrable. Out of 12 carcinogenic compounds, belonging to several different chemical classes, 10 gave rise to an increased UDS, whereas only 2 compounds, the polycyclic aromatic hydrocarbons benzo[alpha]pyrene and benz[alpha]anthracene, did not. All 4 noncarcinogenic compounds tested were negative. Possibly this method can be of value as a routine screening test, in combination with other short-term test systems, thus improving the predictive value of screening in vitro with respect to carcinogenicity.

Animals↗
PubMed2005

Stereolabile chiral compounds: analysis by dynamic chromatography and stopped-flow methods.

Enantiomerization and diastereomerization reactions of chiral compounds play a major role in all aspects of chemistry spanning a wide bridge from drug development to supramolecular chemistry. Traditionally, these reactions are studied by variable-temperature NMR spectroscopy and chiroptical methods such as polarimetry. However, powerful complimentary methods based on chromatography and electrophoresis have been developed and applied to a variety of stereolabile chiral compounds. This tutorial review explains the principles, applications, and limitations of dynamic chromatography and chromatographic and electrophoretic stopped-flow analysis for the investigation of isomerization reactions of chiral compounds.

Chelating Agents↗
PubMed2002

Structure validation of natural products by quantum-mechanical GIAO calculations of 13C NMR chemical shifts.

Geometry optimization and GIAO (gauge including atomic orbitals) (13)C NMR chemical shift calculations at Hartree-Fock level, using the 6-31G(d) basis set, are proposed as a tool to be applied in the structural characterization of new organic compounds, thus providing useful support in the interpretation of experimental NMR data. Parameters related to linear correlation plots of computed versus experimental (13)C NMR chemical shifts for fourteen low-polar natural products, containing 10-20 carbon atoms, were employed to assess the reliability of the proposed structures. A comparison with the hybrid B3LYP method was carried out to evaluate electron correlation contributions to the calculation of (13)C NMR chemical shifts and, eventually, to extend the applicability of such computational methods to the interpretation of NMR spectra in apolar solutions. The method was tested by studying three examples of revised structure assignments, analyzing how the theoretical (13)C chemical shifts of both correct and incorrect structures matched the experimental data.

Biological Products↗
PubMed1985

Evaluation of the mutagenic activity of some aza-aromatic hydrocarbons.

The mutagenic activity of 7 aza-aromatic hydrocarbons, which are suspected of being environmental pollutants, was assessed using the Salmonella assay. The compounds tested were: 1-azachrysene, 2-azachrysene, 4-azachrysene, 1-azabenz[a]anthracene, 2-azabenz[a]anthracene, 9-azabenz[a]anthracene, and 12-benzo[a]pyrene. None of the compounds was mutagenic in the absence of S9, but all were mutagenic in the presence of S9.

Animals↗
PubMed2000

Development and assessment of a 3D pharmacophore for ligand recognition of BDZR/GABAA receptors initiating the anxiolytic response.

Benzodiazepine receptor (BDZR) ligands are structurally diverse compounds that bind to specific binding sites on GABAA receptors and allosterically modulate the effect of GABA on chloride flux. The binding of BDZR ligands to this receptor system results in activity at multiple behavioral end points including anxiolytic, sedative, hyperphagic, anticonvulsant and hyperthermic effects. In the work presented here, 17 structurally diverse BDZR ligands of the receptors initiating the anxiolytic response have been studied using a systematic computational procedure developed in our laboratory. Using this procedure, a five component 3D recognition pharmacophore was obtained consisting of two proton acceptors, a hydrophobic group, an aromatic electron accepting ring and a ring containing polar moieties, all found in a common geometric arrangement in the 15 compounds with an effect at the anxiolytic end point and absent in two control compounds. The 3D pharmacophore developed was validated by searching 3D databases and finding known BDZR ligands active at the anxiolytic end point, including 1,4-BDZ derivatives, imidazo BDZ and beta-carboline ligands.

Anti-Anxiety Agents↗
PubMed2000

Electron and proton reservoir complexes: thermodynamic basis for C-H activation and applications in redox and dendrimer chemistry.

This Account focuses on fundamental aspects and applications of the concept of "electron and proton reservoirs". Permethylated electron reservoir iron sandwich complexes, which were known to be excellent reducing agents in their neutral 19e Fe(I) form, have recently been shown to be stable strong oxidants in their dicationic 17e Fe(III) form. Thermodynamic, mechanistic, and synthetic aspects of the redox chemistry of these and related organoiron complexes are summarized. Proton reservoir properties of these complexes are due to enhanced acidity in their cationic form and result in an original type of activation: perfunctionalization leading to dendritic cores and useful metallodendrimers of variable topology.

Electrons↗
PubMed1990

Mutagenic activity of complex air pollutants in Silesia.

Continuous monitoring of air over the highly industrialized region of Silesia, Poland, shows high pollution with free sedimenting particulate matter, gaseous compounds and metals. Partial chemical analysis of extracts from airborne particulate material revealed over a hundred polycyclic aromatic hydrocarbons (PAHs); 15 major PAHs were evaluated quantitatively at 20 measuring points during summer and winter periods. Both direct and indirect mutagenic activity in extracts of particulate material was observed, with seasonal variations in activity. The direct mutagenic activity was higher in winter samples than in summer ones. Summer samples exhibited high mutagenic activity after metabolic activation of extracts.

Air Pollutants↗