SEARCH · PubMed Health

Results for “HALOGEN COMPOUNDS”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 289 records · Page 16Linked to original sources

PubMed2006

Metabolites from algae with economical impact.

In order to survive in a highly competitive environment, freshwater or marine algae have to develop defense strategies that result in a tremendous diversity of compounds from different metabolic pathways. Recent trends in drug research from natural sources have shown that algae are promising organisms to furnish novel biochemically active compounds. The current review describes the main substances biosynthesized by algae with potential economic impact in food science, pharmaceutical industry and public health. Emphasis is given to fatty acids, steroids, carotenoids, polysaccharides, lectins, mycosporine-like amino acids, halogenated compounds, polyketides and toxins.

Adaptation, Physiological↗

PubMed2001

Biomonitoring of exposure to nitrous oxide, sevoflurane, isoflurane and halothane by automated GC/MS headspace urinalysis.

OBJECTIVES: The goal of the present study was to develop an automated method to assess by biological monitoring, the volatile-anaesthetic exposure (nitrous oxide, sevoflurane, isoflurane and halothane) in operating theatre personnel. METHODS: Post-shift urine samples were analysed by gas chromatography-mass spectrometry coupled with static headspace sampling (GC-MS/ HSS); intra-assay %-RSD (n= 10) was less than 5% for nitrous oxide and less than 7% for each halogenated vapour. The biomonitoring method was validated with air monitoring data, obtained by personal samplers and a similar GC-MS method. The sensitivity achieved by single ion monitoring (SIM) was sufficient to reveal low biological and environmental exposure averages down to 1 microg/l(urine) and 0.5 ppm for nitrous oxide and 0.1 microg/l(urine) and 50 ppb for halogenated compounds, respectively. RESULTS: In 1998 we collected and analysed 714 post-shift urine samples for the biological monitoring of volatile anaesthetics in the urine of the operating-theatre personnel of Sant'Orsola-Malpighi Hospital (Bologna, Italy). Our data showed that nitrous oxide (N20), the anaesthetic most largely used in general anaesthesia, is still the decisive factor in operating-theatre pollution. Moreover, on the basis of our results, working in close contact with anaesthetics seems to be the main determinant of risk: surgical nurses and anaesthesiologists are the most-exposed professional categories (mean post-shift urinary N2O approximately 65 microg/l(urine)) while general theatre staff, surgeons, and auxiliary personnel have significantly lower exposure. CONCLUSIONS: The biological monitoring of post-shift unmodified urinary volatile anaesthetics was confirmed to be a useful tool for evaluating individual exposure to these chemicals. The urinary concentrations of N2O and of halogenated vapours might reflect, to a certain extent, the external exposure to these compounds, and respiratory air-monitoring data support the validity of biological monitoring. Furthermore, the good relationship between air and urinary concentration of anaesthetics in people working in closer contact with these chemicals may be a good indirect means of revealing the bad air conditions of operating rooms, and may contribute to the highlighting and correction of service defects in anaesthesiology equipment and of human errors.

Air Pollution, Indoor↗

PubMed2004

[Influence of 2-aryl-3-halogen/3-hydroxy-1,4-naphthoquinones with salicylic and cinnamic acid partial structures on the arachidonic acid cascade].

Searching for more potent 5-lipoxygenase (LO) inhibitors one tert-butyl group of the selective 5-LO-inhibitor 2-(3,5-di-tert-butyl-4-hydroxyphenyl)-3-hydroxy-1,4-naphthoquinone (1) was substituted by polar functions (-CHO, -COOH, -CH=CH-COOR, -CH2-CH2-COOR). At the same time the 5-LO selectivity of the new compounds within the arachidonic acid cascade was investigated. For this 12-LO- and COX-1-assays with activated human platelets were used. Screening the test compounds new selective 5-LO-inhibitors (4, 9 and 16) and a COX-1-inhibitor (10) as well as dual 5-LO/COX-1- (23) and 12-LO/COX-1- (12) inhibiting compounds were found. Obviously in this class of compounds 5-LO and 12-LO inhibition are mutually excluded for a structural reason. In addition to the well known 3-chloro- (19) and 3-bromo- (20) analogues of 1 the 3-fluoro- (22), 3-iodo- (23) and the 3-carbonitrile- (24) derivatives were synthesized. All 3-halogen compounds, except 23 and the nitrile, are potent non selective inhibitors of all three enzymes. Causative for this unselectivity is the inhibition of the arachidonic acid release by inhibition of the cytosolic phospholipase A2 (cPLA2) with the exception of 24.

Arachidonic Acid↗

PubMed2006

Identification and quantification of polybrominated hexahydroxanthene derivatives and other halogenated natural products in commercial fish and other marine samples.

During routine analysis of commercial fish on halogenated pollutants, an unknown tribromo component (TriBHD) was initially detected as an abundant peak in sample extracts from the Mediterranean Sea. The molecular formula was established to be C16H19Br3O by gas chromatography with electron ionization high-resolution mass spectrometry (GC/EI-HRMS). GC/EI-MS data were virtually identical with a polybrominated hexahydroxanthene derivative (PBHD) previously isolated from an Australian sponge species known to occur in the Mediterranean Sea as well. A tetrabromo isomer (TetraBHD) was also found in the fish samples. The concentrations of TriBHD and other halogenated compounds in commercial fish (sea bass, gilt head bream, anchovy, sardine, and salmon) were estimated with GC/electron capture detection (ECD). Using the ECD response of trans-nonachlor, the concentration of TriBHD reached up to 90 ng/g lipid weight and accounted for up to >90% of the concentration of p,p'-DDE, which was the most abundant peak in the most samples investigated. On the basis of the GC/ECD response, TetraBHD amounted for approximately 1/7 of TriBHD in all fish samples investigated. The sample with the highest content was a green-lipped mussel from New Zealand (236 ng/g lipid weight). The halogenated natural products TBA, Q1, and MHC-1 were also present in most of the samples. We assume that the bulk of the residues in fish from aquaculture may originate from algae and sponges living in proximity of the fish farms. Detection of TriBHD and TetraBHD in blubber of a monk seal (Monachus monachus) suggests that both HNPs may reach the top predators of food webs and thus also humans.

Animals↗

PubMed2000

Analytical techniques used for monitoring the biodegradation of fluorinated compounds in waste streams from pharmaceutical production.

During the assessment of the environmental impact of new pharmaceutical processes the selection and testing of suitable environmental treatment technologies is carried out. A large component of process waste stream treatment practice is aerobic biotreatment in wastewater treatment plants, as it is cost effective and generally more environmentally friendly than harsher chemical/physical treatments. Pharmaceutical syntheses use a range of halogenated compounds (either as reagents, solvents or intermediates) which pose particular challenges to microbial degradation. This is especially so for some fluorinated compounds due to the resilience to enzymatic cleavage of the C-F bond in some cases. The data presented here were obtained from a case study involving the monitoring of the biodegradation of 4-fluorocinnamic acid by means of a range of chromatographic techniques. These methods were used to monitor not only the disappearance of the compound but also the formation of degradation products in order to confirm mineralisation. In addition mass spectrometry was used to elucidate the metabolic pathway.

Biodegradation, Environmental↗

PubMed1990

Determination of non-metallic elements by capacitively coupled helium microwave plasma atomic emission spectrometry with capillary gas chromatography.

A capacitively coupled microwave helium plasma with a tubular tantalum electrode was evaluated as an element selective detector for gas chromatography (GC). The end of a 10-m bonded fused capillary column was directly inserted into the tubular electrode without any switching system. A heated copper tube was used to house the part of the GC column that protruded from the oven. The optimisation of operating parameters, line selection, background emission and horizontal and vertical observation position is described. Analytical figures of merit including sensitivity, reproducibility, signal to background ratio, selectivity, dynamic range and limit of detection (LOD), were evaluated for carbon, hydrogen, chlorine and bromine emission. Limits of detection in the low ng range (20 pmol) were obtained for halogenated compounds using carbon emission, whereas LODs in the 0.1 micrograms range (2 nmol) were obtained using chlorine or bromine emission lines.

Bromine↗

PubMed1988

Prediction of retention indexes. I. Structure-retention index relationship on apolar columns.

A simple method is reported for predicting the retention index (RI) of a chemical compound from the number of carbon and carbon equivalent atoms in the molecule, the RI increment for atom addition and the group retention factors (GRFs) for substituents and functional groups. Atoms other than carbon such as oxygen, nitrogen, sulfur, chlorine, bromine and iodine are assigned carbon atom equivalency of approximately 1, 1, 2, 2, 3 and 4, respectively and are counted for their contribution towards RI prediction. The GRFs of substituents and functional groups are derived from the RIs of reference compounds and series of homologues. Ring structures, ring fusion, ring connection, iso- and neo-carbons, chain branching and unsaturation are also assigned GRFs. The predicted RIs of a number of alicyclic, aliphatic and aromatic hydrocarbons, primary, secondary and tertiary alcohols, phenols, aliphatic amines, aromatic amines, heterocyclics, carboxylic acids, acid esters, aldehydes, ketones, and halogenated compounds, are found to be within +/- 3% of the observed values. The structure-retention index relationship thus developed is extremely useful in the tentative identification of radioactive side products formed in tritium labeling by radiation-induced methods.

Alcohols↗

PubMed1985

Biotransformation of halogenated solvents.

The toxicity of most halogenated solvents is associated with their biotransformation. The bioactivation can be due to the formation of stable, toxic metabolites or the formation of reactive, electrophilic intermediates. The paper summarizes present knowledge on the biotransformation of several halogenated compounds, ie, methyl halides, methylene halides, haloforms, carbon tetrachloride, chlorinated ethanes, and chlorinated alkenes. Some of the relevant enzymatic metabolic reactions are also discussed.

Animals↗

PubMed2003

Catalytic mechanism of the maloalkane dehalogenase LinB from Sphingomonas paucimobilis UT26.

Haloalkane dehalogenases are bacterial enzymes capable of carbon-halogen bond cleavage in halogenated compounds. To obtain insights into the mechanism of the haloalkane dehalogenase from Sphingomonas paucimobilis UT26 (LinB), we studied the steady-state and presteady-state kinetics of the conversion of the substrates 1-chlorohexane, chlorocyclohexane, and bromocyclohexane. The results lead to a proposal of a minimal kinetic mechanism consisting of three main steps: (i) substrate binding, (ii) cleavage of the carbon-halogen bond with simultaneous formation of an alkyl-enzyme intermediate, and (iii) hydrolysis of the alkyl-enzyme intermediate. Release of both products, halide and alcohol, is a fast process that was not included in the reaction mechanism as a distinct step. Comparison of the kinetic mechanism of LinB with that of haloalkane dehalogenase DhlA from Xantobacter autotrophicus GJ10 and the haloalkane dehalogenase DhaA from Rhodococcus rhodochrous NCIMB 13064 shows that the overall mechanisms are similar. The main difference is in the rate-limiting step, which is hydrolysis of the alkylenzyme intermediate in LinB, halide release in DhlA, and liberation of an alcohol in DhaA. The occurrence of different rate-limiting steps for three enzymes that belong to the same protein family indicates that extrapolation of this important catalytic property from one enzyme to another can be misleading even for evolutionary closely related proteins. The differences in the rate-limiting step were related to: (i) number and size of the entrance tunnels, (ii) protein flexibility, and (iii) composition of the halide-stabilizing active site residues based on comparison of protein structures.

Carbon↗

PubMedDate not supplied

Quantum mechanical structure-activity relationship analyses for skin sensitization.

Allergic contact dermatitis (ACD) results in inflammation of the skin due to sensitization of the immunologic system to a particular substance. The sensitization process is limited by the compound's ability to both permeate and react with proteins in the integumentary system. Currently, only in vivo animal tests such as the local lymph node assay (LLNA) are recognized by regulatory authorities for risk assessment of ACD. A quantitative structure-activity relationship has been developed to predict relative potency, which allows for the prediction of relative sensitization potentials. The experimental values used in this study include EC3 values (the concentration at which the stimulation index equals 3) from LLNA tests. The predictions in this model enable categorization of the compounds into three groups on the basis of risk of sensitization and enable screening of candidate molecules using rapid SAM1 semiempirical calculations prior to animal testing. The model may also be used to reduce the number of animals subjected to testing by providing estimated concentrations required for useful data of risk assessment. The effect of averaging available literature values on predictive ability is also investigated. The model includes halogenated compounds, aromatic compounds, alcohols, aldehydes, and ketones. The computational investigation resulted in a two-descriptor model that is consistent with the assumed mechanism for sensitization.

Hypersensitivity↗

PubMed2004

The metabolic rate constants and specific activity of human and rat hepatic cytochrome P-450 2E1 toward toluene and chloroform.

Chloroform (CHCl3) is a near-ubiquitous environmental contaminant, a by-product of the disinfection of drinking water sources and a commercially important compound. Standards for safe exposure have been established based on information defining its toxicity, which is mediated by metabolites. The metabolism of CHCl3 is via cytochrome P-450 2E1 (CYP2E1)-mediated oxidation to phosgene, which is known to obey a saturable mechanism. CYP2E1 is a highly conserved form, expressed in all mammalian systems studied, and is responsible for the metabolism of a great many low-molecular-weight (halogenated) compounds. However, the Michaelis-Menten rate constants for CHCl3 oxidation have not been derived in vitro, and the specific activity of CYP2E1 toward CHCl3 has not been reported. In this investigation with microsomal protein (MSP), apparent Vmax values of 27.6 and 28.3 nmol/h/mg MSP and apparent K(m) values of 1 and 0.15 microM in rats and human organ donors, respectively, were demonstrated. The specific activity of CYP2E1 toward CHCl3 in rats and humans was 5.29 and 5.24 pmol/min/pmol CYP2E1, respectively. Toluene metabolism to benzyl alcohol (BA), another CYP2E1-dependent reaction, was also highly dependent on CYP2E1 content in humans, and was more efficient than was CHCl3 metabolism. The specific activity of human CYP2E1 toward toluene metabolism in human MSP was 23 pmol/min/pmol CYP2E1. These results demonstrate that differences in CYP2E1 content of MSP among individuals and between species are largely responsible for observed differences in toluene and CHCl3 metabolism in vitro.

Adult↗

PubMed2006

Determination of a wide range of volatile and semivolatile organic compounds in snow by use of solid-phase micro-extraction (SPME).

Quantification and transformation of organic compounds are pivotal in understanding atmospheric processes, because such compounds contribute to the oxidative capacity of the atmosphere and drive climate change. It has recently been recognized that chemical reactions in snow play a role in the production or destruction of photolabile volatile organic compounds (VOC). We present an environmentally friendly method for determination of VOC and semi-VOC in snow collected at three sites-remote, urban, and (sub-)arctic. A solid-phase micro-extraction (SPME) procedure was developed and (semi-)VOC were identified by gas chromatography with mass spectrometric detection (GC-MS). A broad spectrum of (semi-)VOC was found in snow samples, including aldehydes, and aromatic and halogenated compounds. Quantification was performed for 12 aromatic and/or oxygenated compounds frequently observed in snow by use of neat standard solutions. The concentrations detected were between 0.12 (styrene and ethylbenzene) and 316 microg L(-1) (toluene) and limits of detection varied between 0.11 (styrene) and 1.93 microg L(-1) (benzaldehyde). These results indicate that the SPME technique presented is a broad but selective, versatile, solvent-free, ecological, economical, and facile method of analysis for (semi-)VOC in natural snow samples.

Journal Article↗

PubMed1991

Performance of 133 compounds in the lambda prophage induction endpoint of the Microscreen assay and a comparison with S. typhimurium mutagenicity and rodent carcinogenicity assays.

The Microscreen assay was developed as a means of testing very small samples, as in complex mixture fractionation. It is a multi-endpoint assay which utilizes E. coli WP2s(lambda). Exposure takes place to serial dilutions of the test compound in microtitre wells (250 microliters) followed by sampling from wells in which growth has occurred ('non-toxic wells'). Although a number of different endpoints can be measured, only the prophage induction endpoint (the first one developed) has been extensively tested. Results with 133 compounds are presented. These include 111 compounds which have been tested in the S. typhimurium assay and 66 compounds for which both rodent bioassay and S. typhimurium assay data exists. The concordance for the Microscreen assay and the S. typhimurium assay was 71%. For this group of compounds, the sensitivity of the Microscreen assay in detecting carcinogens was 76% compared with 58% for the S. typhimurium assay. However, the S. typhimurium assay was somewhat more specific (69%) compared with the Microscreen (56%). The overall association between carcinogenicity and Microscreen results was statistically significant (p = 0.029), whereas for the S. typhimurium assay the association with carcinogenicity was non-significant (p = 0.086). The Microscreen assay was able to detect halogenated compounds better than the S. typhimurium assay. The Microscreen assay should prove useful in complex mixture fractionation, or in other situations where sample size is limiting.

Animals↗

PubMed2000

Dehalogenation of haloalkanes by Mycobacterium tuberculosis H37Rv and other mycobacteria.

Haloalkane dehalogenases convert haloalkanes to their corresponding alcohols by a hydrolytic mechanism. To date, various haloalkane dehalogenases have been isolated from bacteria colonizing environments that are contaminated with halogenated compounds. A search of current databases with the sequences of these known haloalkane dehalogenases revealed the presence of three different genes encoding putative haloalkane dehalogenases in the genome of the human parasite Mycobacterium tuberculosis H37Rv. The ability of M. tuberculosis and several other mycobacterial strains to dehalogenate haloaliphatic compounds was therefore studied. Intact cells of M. tuberculosis H37Rv were found to dehalogenate 1-chlorobutane, 1-chlorodecane, 1-bromobutane, and 1,2-dibromoethane. Nine isolates of mycobacteria from clinical material and four strains from a collection of microorganisms were found to be capable of dehalogenating 1,2-dibromoethane. Crude extracts prepared from two of these strains, Mycobacterium avium MU1 and Mycobacterium smegmatis CCM 4622, showed broad substrate specificity toward a number of halogenated substrates. Dehalogenase activity in the absence of oxygen and the identification of primary alcohols as the products of the reaction suggest a hydrolytic dehalogenation mechanism. The presence of dehalogenases in bacterial isolates from clinical material, including the species colonizing both animal tissues and free environment, indicates a possible role of parasitic microorganisms in the distribution of degradation genes in the environment.

Alkanes↗

PubMed1972

The metabolism of fluoroacetate in lettuce.

1. Whole lettuce plants were incubated with (1) [1-(14)C]acetate, (2) fluoroacetate followed by [1-(14)C]acetate, (3) fluoro[1-(14)C]acetate, (4) fluoro[2-(14)C]acetate or (5) S-carboxy[(14)C]methylglutathione. 2. Fluoroacetate did not affect the expiration of (14)CO(2) from [1-(14)C]acetate and only a small amount of (14)CO(2) was produced from either fluoro[1-(14)C]-acetate or fluoro[2-(14)C]acetate in 43h. 3. Fluoroacetate at 50mg/kg wet wt. doubled the plant citrate concentration after 43h incubation, and depending on the age and size of the plant 50-100% of the compound was metabolized. 4. With both fluoro[1-(14)C]acetate and fluoro[2-(14)C]acetate all the radioactivity except that in the CO(2) was found in the water-soluble acid fraction. About 2% was in fluorocitrate and the remainder, apart from unchanged fluoroacetate, was in a number of compounds devoid of fluorine but containing nitrogen and sulphur. These were peptide-like and could be separated by chromatography on an amino acid analyser. 5. Identical compounds were obtained from the spontaneous reaction between iodo[2-(14)C]acetate and glutathione, the major product being S-carboxymethylglutathione. 6. S-Carboxymethylcysteine was also isolated and its mass spectrum compared with a commercial sample. 7. Reaction rates of all the monohaloacetates with glutathione were studied at pH7 at 25 degrees C. No reaction was observed with fluoroacetate. 8. The metabolism of fluoroacetate by lettuce is discussed in relation to that of aliphatic and aromatic halogen compounds, including fluoroacetate, by mammalian liver and to the metabolism of fluoroacetate by different plants reported by other workers.

Amino Acids↗

PubMed2001

Construction and validation of automated purge-and-trap-gas chromatography for the determination of volatile organic compounds.

An automated purge-and-trap chromatographic system for the determination of dissolved volatile organic compounds in aqueous samples was built in the laboratory with minimum cost both in the construction and routine operation. This system was built upon a commercial gas chromatograph with full automation capability using self-developed hardware and software. The use of a multi-sorbent bed quantitatively trapped a wide range of volatile organic compounds at ambient temperature, including the extremely volatile ones such as dichlorofluoromethane (CFC-12). Flash heating for rapid desorption and adequate plumbing for minimizing dead volume resulted in excellent chromatographic separation at above-ambient temperatures, which eliminated the need for cryogen for cooling at the head of the column, a second refocusing stage, or entire GC oven for refocusing. This cryogen-free system was tested with standard solutions and environmental samples for determining hydrocarbons with flame ionization detection, and halogenated compounds with electron-capture detection. An innovative method was also developed for validating the system's linearity for extremely volatile compounds. By introducing ambient air, which usually contains constant levels of anthropogenic halocarbons, e.g., CFC-12 and CFC-11 (CCl3F), the need to prepare aqueous standards containing extremely volatile compounds is avoided, hence providing a convenient method for evaluating a purge-and-trap system.

Automation↗

PubMed2006

Halogenation of 4-hydroxy-3-methoxybenzyl thiourea TRPV1 agonists showed enhanced antagonism to capsaicin.

Selected potent TRPV1 agonists (1-6) have been modified by 5- or 6-halogenation on the aromatic A-region to analyze their effects on potency and efficacy (agonism versus antagonism). The halogenation caused enhanced functional antagonism at TRPV1 compared to the corresponding prototype agonists. The analysis of SAR indicated that the antagonism was enhanced as the size of the halogen increased (I>Br>Cl) and when the 6-position was halogenated. Compounds 23c and 31b were found to be potent full antagonists with K(i) (as functional antagonist)=23.1 and 30.3 nM in rTRPV1/CHO system, respectively.

Animals↗

PubMed1981

Toxic drug effects associated with oxygen metabolism: redox cycling and lipid peroxidation.

Various endogenous and exogenous compounds exert cytotoxic effects via oxygen reduction. In general, these are reduced by intracellular enzymes (reductases of various kinds) in one-electron transfer reactions, before they in turn reduce O2 to O2, the superoxide anion radical. Thus, a cycle is formed of O2 uptake at the expense of cellular reducing equivalents, notably NADPH, generating further active oxygen species (figs 1,2). Structures capable of 'redox cycling' include catechols and other quinone compounds, iron chelates, and aromatic nitro compounds. Several anticancer agents, and also some mutagens, operate on this principle, and their toxic effects may be explained by redox cycling. The particular importance of hypoxic conditions for deleterious O2 effects is given by the concomitant flux through reductive as well as oxidative pathways. Toxic effects include membrane damage resulting from peroxidative reactions of polyunsaturated fatty acids (lipid peroxidation), as well as the attack of reactive oxygen species on proteins (enzymes) and nucleic acids; thus O2 metabolism is linked to carcinogenicity and mutagenicity. Lipid peroxidation is also induced by various halogenated compounds such as carbon tetrachloride. Again, hypoxic conditions are particularly critical because, on the one hand, metabolic activation leading to the free radical is enhanced and, on the other hand, oxygen required for the maintenance of lipid peroxidation is still available. - Powerful antioxidant systems of the cell maintain low steady state concentrations of oxygen metabolites, and toxic effects may, in part, also be explained by the constant drain of reducing equivalents resulting from redox cycling.

Anaerobiosis↗