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At least 19 recordsLinked to original sources
PubMed1980

Chemical structure and biodegradability of halogenated aromatic compounds. Halogenated muconic acids as intermediates.

Substituted muconic acids were prepared from the corresponding catechols by pyrocatechase II from Pseudomonas sp. B13. The stabilities of substituted muconic acids were compared under different pH conditions. 3-Substituted cis, cis-muconic acids cycloisomerized readily in slightly acidic solutions, whereas 2-chloro- and 2-fluoro-cis,cis-muconic acids were stable under these conditions and could be isolated as crystalline compounds. They were isomerized to the cis, trans-form in highly acidic solution (pH 1), particularly when heated to 80 degrees C. Cycloisomerization of 2-chloro-cis,cis-muconic acid in 75% (v/v) H2SO4 yields 4-carboxymethyl-2-chloro-but-2-en-4-olide (4-chloro-2,5-dihydro-5-oxo-3H-furan-2-ylacetic acid). THe cis,cis-configuration of 2-chloromuconic acid was certified by 1H n.m.r. spectroscopy and by enzymic cycloisomerization. Although the cis,cis-configuration of 2-fluoromuconic acid was confirmed by corresponding spectroscopic data, it was not cycloisomerized by crude extracts or cycloisomerase II preparations from Pseudomonas sp. B13.

Biodegradation, Environmental↗
PubMed1991

Biotransformation of halogenated compounds.

As a result of natural production and contamination of the environment by xenobiotic compounds, halogenated substances are widely distributed in the biosphere. Concern arises as a result of the toxic, carcinogenic, and potential teratogenic nature of these substances. The biotransformations of such halogenated substances are reviewed, with particular emphasis on the biocatalytic cleavage of the carbon-halogen bonds. The physiology, biochemistry, and genetics of the biological system involved in the dehalogenation reactions are discussed for three groups of organohalogens: (1) the haloacids, (2) the haloaromatics, and (3) the haloalkanes. Finally, the biotechnological applications of these microbial transformations are discussed. This includes prospects for their future application in biosynthetic processes for the synthesis of halogenated intermediates or novel compounds and also the use of such systems for the detoxification and degradation of environmental pollutants.

Bacteria↗
PubMed1984

Metabolism of genotoxic agents: halogenated compounds.

Most halogenated compounds showing genotoxicity do not themselves react with macromolecules but are transformed to reactive metabolites. In order to explain the widely different genotoxicities of halogenated ethylenes, the 'optimum stability' theory of epoxides has been developed recently. An epoxide must be reactive to alkylate DNA, but stable enough to reach the target from the place of its formation. Also, pharmacokinetic aspects are important in accounting for differences in genotoxicities of closely related compounds; examples are provided. Reactive metabolites may bind to proteins, to lipids and coenzymes, and to DNA, but binding to targets other than DNA is far more common than DNA alkylation. An example is provided by investigations on 2,2'-dichlorodiethyl ether from which chloroacetaldehyde is formed. In contrast to vinyl chloride, which generates chloroethylene oxide (chlorooxirane) as well as chloroacetaldehyde, this compound leads to extensive covalent protein binding of metabolites, but not to DNA binding.

Alkylating Agents↗
PubMed1993

Human glutathione S-transferase-expressing Salmonella typhimurium tester strains to study the activation/detoxification of mutagenic compounds: studies with halogenated compounds, aromatic amines and aflatoxin B1.

We have developed Salmonella typhimurium strains expressing human glutathione S-transferases (GSTs) to establish the role of these enzymes in chemical activation and deactivation. Alpha and pi class GSTs, GSTA1-1 and GSTP1-1, were expressed in Salmonella TA100 using a regulatable tac promoter expression system. The ability of these GST to modulate the mutagenicity of a range of mutagens including ethylene dibromide, ethylene dichloride and methylene dichloride was then investigated. Ethylene dibromide, ethylene dichloride and methylene dichloride were directly mutagenic in the control TA100 strain. The mutagenicity of ethylene dibromide and ethylene dichloride was increased in cells expressing GSTA1-1, but not in cells expressing GSTP1-1. In contrast, methylene dichloride mutagenicity was unaffected by the presence of either GST. The mutagenicity of 2-aminofluorene, was not altered by the presence of either GST isozyme, while that of N-hydroxy-2-acetylaminofluorene was slightly reduced with both isozymes. The mutagenicity of aflatoxin B1 (AFB1) was marginally decreased in strains expressing GSTP1-1. When GSTA1-1 expression was maximally induced, however, a more pronounced reduction was observed suggesting a role for GSTA1-1 in AFB1 deactivation. The tester strains described here should be valuable in establishing the specificity of human GST isozymes towards chemical toxins and carcinogens, especially for compounds whose reactive intermediates are short lived.

Aflatoxin B1↗
PubMed1992

In vivo studies on halogen compound interactions. IV. Interaction among different halogen derivatives with and without synergistic action on liver toxicity.

The liver toxicity of several halogen compound mixtures have been tested. The compounds were selected on the basis of their metabolic pathways: carbon tetrachloride (CT) and trichlorobromomethane (TCBM) undergo a dehalogenation via P450-dependent enzyme system, 1,2-dichloroethane (DCE) and 1,2-dibromoethane (DBE) are mainly conjugated with the cytosolic glutathione (GSH) by means of the GSH-S-transferase. The mixture TCBM+DBE shows a more than additive action on lipid peroxidation and liver necrosis. TCBM, like CT, reduces the hepatic level of GSH-S-transferase, increasing the amount of DBE available for cytochrome P450-dependent metabolism, with the production of toxic metabolites. Thus, the behavior of the mixture TCBM+DBE is very similar to that of the mixture CT+DBE, previously reported. Mixtures composed of CT+TCBM and DCE+DBE do not show any synergistic effect on liver toxicity. The results allow one to conclude that the toxicity of mixtures of halogen compounds can be partly predicted on the basis of their metabolic pathways. When the metabolism is quite different, a synergistic toxicity can occur if one pathway interferes with a detoxification mechanism of the other compound. If the two metabolisms are very similar they produce, at most, an additive toxicity.

Alanine Transaminase↗
PubMed2006

The origin of stable halogenated compounds in volcanic gases.

BACKGROUND: Halogenated compounds in the atmosphere are of great environmental concern due to their demonstrated negative effect on atmospheric chemistry and climate. Detailed knowledge of the emission budgets of halogenated compounds has to be gained to understand better their specific impact on ozone chemistry and the climate. Such data are also highly relevant to guide policy decisions in connexion with international agreements about protection of the ozone layer. In selected cases, the relevance of specific emission sources for certain compounds were unclear. In this study we present new and comprehensive evidence regarding the existence and relevance of a volcanic contribution of chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs), hydrochlorofluorocarbons (HCFCs), halons (bromine containing halo(hydro)carbons), and fully fluorinated compounds (e.g. CF4 and SF6) to the atmospheric budget. METHODS: In order to obtain new evidence of a volcanic origin of these compounds, we collected repeatedly, during four field campaigns covering a period of two years, gases from fumaroles discharging over a wide range of temperatures at the Nicaraguan subduction zone volcanoes Momotombo, Cerro Negro and Mombacho, and analysed them with very sensitive GC/MS systems. RESULTS AND DISCUSSION: In most fumarolic samples certain CFCs, HFCs, HCFCs, halons, and the fully fluorinated compounds CF4 and SF6 were present above detection limits. However, these compounds occur in the fumarole gases in relative proportions characteristic for ambient air. CONCLUSION: This atmospheric fingerprint can be explained by variable amounts of air entering the porous volcanic edifices and successively being incorporated into the fumarolic gas discharges. Recommendation and Outlook. Our results suggest that the investigated volcanoes do not constitute a significant natural source for CFCs, HFCs, HCFCs, halons, CF4, SF6 and NF3.

Air Pollutants↗
PubMed2000

Anaerobic decomposition of halogenated aromatic compounds.

Halogenated compounds constitute one of the largest groups of environmental pollutants, partly as a result of their widespread use as biocides, solvents and other industrial chemicals. A critical step in degradation of organohalides is the cleavage of the carbon?halogen bond. Reductive dehalogenation is generally the initial step in metabolism under methanogenic conditions, which requires a source of reducing equivalents, with the halogenated compound serving as an electron acceptor. Dehalogenation is greatly influenced by alternate electron acceptors; e.g. sulfate frequently inhibits reductive dehalogenation. On the other hand, a number of halogenated aromatic compounds can be degraded under different electron-accepting conditions and their complete oxidation to CO(2) can be coupled to processes such as denitrification, iron(III)-reduction, sulfate reduction and methanogenesis. Reductive dehalogenation was the initial step in degradation not only under methanogenic, but also under sulfate- and iron(III)-reducing conditions. Dehalogenation rates were in general slower under sulfidogenic and iron-reducing conditions, suggesting that dehalogenation was affected by the electron acceptor. The capacity for dehalogenation appears to be widely distributed in anoxic environments; however, the different substrate specificities and activities observed for the halogenated aromatic compounds suggest that distinct dehalogenating microbial populations are enriched under the different reducing conditions. Characterization of the microbial community structure using a combination of biomolecular techniques, such as cellular fatty acid profiling, and 16 S rRNA fingerprinting/sequence analysis, was used to discern the distinct populations enriched with each substrate and under each electron-accepting condition. These combined techniques will aid in identifying the organisms responsible for dehalogenation and degradation of halogenated aromatic compounds.

Journal Article↗
PubMed1978

The detection and identification of unknown halogenated compounds in environmental samples.

A new method is described in which the mass spectrometer is an element specific detector for a gas chromatograph. The elements investigated in this study are F, Cl, Br, J, S and N, but the method might be applied to other elements as well. The molecules coming from the gas chromatograph are atomized in a microwave induced discharge, located in the interface between the gaschromatograph and the mass spectrometer. Unknown compounds containing specific elements can be detected and their retention times can be determined. The method is applied to samples of surface water, fat of a grebe and human adipose tissue for halogenated compounds. Unknown halogenated compounds were found. A number of them were identified in samples of surface water.

Adipose Tissue↗
PubMed1991

Measurement of organic halogen compounds in urine as an indicator of exposure.

The report describes the measurement of urinary organic halogen compounds. The method is an application of the adsorbable organic halogen assay which is widely used for the analysis of industrial waste water and drinking water. It was found that this assay can be applied to human urine if the urine is pretreated to hydrolyze the mucins so as to cleave the neuraminic acid residues responsible for the high viscosity of these slimy proteins. The method was found to be sensitive down to 1 microgram of organic halogen/100 ml of urine. Fifty to 260 micrograms of organic halogen was measured in the night urine of healthy, occupationally unexposed volunteers. Since many toxic chemicals to which man may be exposed environmentally or occupationally are, in fact, halogen compounds, this assay may be used to monitor for human exposure.

Adolescent↗
PubMedDate not supplied

[Presence of disinfection by-products (DBPs) and other halogenated compounds in drinking water samples collected in the areas of Modena and Parma].

The Authors report data about the presence of Disinfection By-Products (DBPs) and other halogenated compounds in drinking water samples collected in the areas of Modena and Parma (20 water supplies). Trihalomethanes, chlorite and chlorate (only in water samples treated with chlorine dioxide), and halogenated compounds were investigated. On the whole, trihalomethanes were evidenced in the 85% of the samples (n. 285) at low levels, while chlorite and chlorate were present in the 67% and 63% of the treated samples with chlorine dioxide (257 samples). Chlorite mean and median values were 225.70 microg/l and 136.75 microg/l respectively, ranging from 20 to 2000 microg/l. Chlorate concentrations were lower than chlorite: the mean value was 102.93 mg/l, while median level was 50 microg/l (range: 20-1500 microg/l). The high concentrations of chlorite and the wide range of values within each municipality plant in Modena and Parma suggest to investigate further in order to evaluate the human exposure in drinking water thoroughly.

Chlorine Compounds↗
PubMed1991

Validated methods for degrading hazardous chemicals: some halogenated compounds.

Two techniques were investigated for degrading a number of halogenated compounds of commercial and research importance. Reductive dehalogenation with nickel-aluminum alloy in potassium hydroxide solution was used to degrade iodomethane, chloroacetic acid, trichloroacetic acid, 2-chloroethanol, 2-bromoethanol, 2-chloroethylamine, 2-bromoethylamine, 1-bromobutane, 1-iodobutane, 2-bromobutane, 2-iodobutane, 2-bromo-2-methylpropane, 2-iodo-2-methylpropane, 3-chloropyridine, fluorobenzene, chlorobenzene, bromobenzene, iodobenzene, 4-fluoroaniline, 2-chloroaniline, 3-chloroaniline, 4-chloroaniline, 4-fluoronitrobenzene, 2-chloronitrobenzene, 3-chloronitrobenzene, 4-chloronitrobenzene, benzyl chloride, benzyl bromide, alpha,alpha-dichlorotoluene, and 3-aminobenzotrifluoride. The products were generally those obtained by replacing the halogen with hydrogen although concomitant reduction of the other groups was also observed. Bibenzyl was produced during the reduction of benzyl chloride, benzyl bromide, and alpha,alpha-dichlorotoluene. Refluxing with ethanolic potassium hydroxide was used to degrade iodomethane, chloroacetic acid, 2-fluoroethanol, 2-chloroethanol, 2-bromoethanol, 1-chlorobutane, 1-bromobutane, 1-iodobutane, 2-bromobutane, 2-iodobutane, 2-bromo-2-methylpropane, 2-iodo-2-methylpropane, benzyl chloride, benzyl bromide, 1-bromononane, 1-chlorodecane, and 1-bromodecane. The products were the corresponding ethyl ethers. 2-Methylaziridine was cleaved with nickel-aluminum alloy in potassium hydroxide solution to a mixture of isopropylamine and n-propylamine. In all cases, the compounds were completely degraded and only nonmutagenic reaction mixtures were produced.

Hazardous Substances↗
PubMed1987

Halogenated compounds as inducers of lipid peroxidation in tissue slices.

Twenty-seven halogenated compounds were screened as potential inducers of lipid peroxidation in rat liver, kidney, spleen, and testes slices. In addition to the known lipid peroxidation inducers--carbon tetrachloride and bromotrichloromethane--the novel compounds carbon tetrabromide, p-bromobenzyl bromide, and benzyl bromide increased lipid peroxidation in each of the tissues studied. Lipid peroxidation was measured by release of thiobarbituric acid-reactive substances (TBARS) from the tissue slices. The amount of TBARS released from liver slices incubated with bromotrichloromethane, carbon tetrabromide, dichloromethane, bromobenzene, chloroform, bromoform, benzyl chloride, bromochloromethane, and carbon tetrabromide correlated with the lethality of these compounds as evaluated by their oral LD50 in rats. The lethality of a number of the compounds tested did not correlate with their capacity to induce lipid peroxidation.

Animals↗
PubMed1977

Synthesis and topical antiinflammatory properties of 17,21-bis(acetyloxy)-6beta,9-difluoro-11beta-hydroxypregna-1,4-diene-3,20-dione and related 2-halogenated compounds.

Introduction of a halogen atom at C-2 of steroid 3-ketofluorohydrins, obtained from the corresponding 5alpha,6alpha-epoxides by trans-diaxial opening with hydrofluoric acid, prevents the 6beta-fluorine atom from undergoing rearrangement to the more stable 6alpha configuration when the 5-tert-hydroxyl is split off to yield to yield a conjugated double bond. Two processes were investigated for the synthesis of 17,21-bis(acetyloxy)-6beta-fluoro-1,4,9(11)-triene-3,20-dione (24a) and the related 2-bromo compound 24b starting from the known 21-(acetyloxy)-6beta-fluoro-5alpha,11alpha,17-trihydroxypregnane-3,20-dione (13). Successive reaction with hypobromous acid, epoxidation, and fluorination converted 24a and 24b into the title compound 27a and the analogue 2-bromo compound 27b. In addition, a synthesis of 17,21-bis(acetyloxy)-2-chloro-6beta,9-difluoropregna-1,4-diene-3,20-dione (27c) is reported. The antiinflammatory activity of 17,21-bis-(acetyloxy)-6beta,9-difluoropregna-1,4-diene-3,20-dione (27a) and its 2-halogenated analogues 27b and 27c in comparison with the corresponding 6alpha,9-difluoro epimers was studied. Some 6beta-fluoro compounds displayed high topical antiinflammatory activity without systemic effects.

Administration, Oral↗
PubMed1993

The groundwater pollution in Lombardy (north Italy) caused by organo-halogenated compounds.

This paper deals with the phenomenon of the presence of organo-halogenated compounds in groundwaters of the Lombardy Region (North Italy). The regionwide study evidentiated the magnitude of the phenomenon, since these compounds are employed in all productive and household activities. The main cause of groundwater contamination is the infiltration of industrial wastewater: in the Province of Mantova, for example, organic chlorinated solvents have their origin in the NaOCl wastewater treatment for ammonia removal. Organic alogenated compounds in waters intended for human consumption in Lombardy are present in 510 wells over 92 townships, affecting a population of 1,934,133 equivalent to 20% of the total resident population (1991 data). Maximum observed concentrations are related to trielin and tetrachloroethilene. Water treatment was achieved through aeration (stripping) and activated carbon or resin adsorption; in a few instances, also hydraulic interventions were implemented.

Hydrocarbons, Halogenated↗