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PubMed2007

Bond orders and atomic properties of the highly deformed halogenated fullerenes C60F18 and C60Cl30 derived from their charge densities.

The experimental charge densities of the halogenated C(60) fullerenes C(60)F(18) and C(60)Cl(30) were determined from high-resolution X-ray data sets measured with conventional Mo(Kalpha) radiation at 20 K for C(60)Cl(30) and with synchrotron radiation at 92 K for the fluorine compound. Bond topological and atomic properties were analyzed by using Bader's AIM theory. For the different C--C bonds, which vary in lengths between 1.35 and 1.70 A bond orders n between n=2 and significantly below n=1 were calculated from the bond topological properties at the bond critical points (BCP's). The low bond orders are seen for 5/6 bonds with each contributing carbon carrying a halogen atom. By integration over Bader's zero flux basins in the electron density gradient vector field atomic properties were also obtained. In contrast to free C(60), in which all carbon atoms have a uniform volume of 11 A(3) and zero charge, atomic volumes vary roughly between 5 and 10 A(3) in the halogenated compounds. Almost zero atomic charges are also found in the Cl derivative but a charge separation up to +/-0.8 e exists between C and F in C(60)F(18) due to the higher fluorine electronegativity, which is also seen in the electrostatic potential for which the electronegativity difference between carbon and fluorine, and the addition to one hemisphere of the fullerene cage leads to a strong potential gradient along the C(60)F(18) molecule. From the summation over all atomic volumes it follows that the halogen addition does not only lead to a dramatic distortion of the C(60) cage but also to a significant shrinkage of its volume.

Journal Article↗
PubMedDate not supplied

[Fertility of workers exposed to herbicides and pesticides].

Twenty-one workmen exposed to herbicide as organic mercury compounds and to pesticide as halogenic hydrocarbon has been investigated concerning their fertility. If the concentrations of organic mercury compounds increase in the air of the place of employment then the levels of this heavy metal are also higher in the urine and in the ejaculate, and the fertility is reduced. It could also be established that a correlation exists between the concentration of pesticide in the place of employment and the male fertility, especially in cases with an excess of maximum permitted concentrations.

Adult↗
PubMed2005

Spectrophotometric determination of the dissociation constants of crown ethers with grafted acridone unit in methanol based on Benesi-Hildebrand evaluation.

As potential chromo- and fluorophores for optical sensors a number of acridone grafted crown ethers containing NO2 group(s) and/or Br or Cl atom(s) in the aromatic rings (compounds) were studied by spectrophotometric method. In the first step of this work the acid-base and complexing properties of these compounds as well as those of the acridone, thioacridone and 4,5-dinitroacridone were investigated. Compounds proved to be very week acids and therefore the conventional spectrophotometric method based on the measurement of the ratio of the protonated/deprotonated forms of the compounds was not applicable for the determination of the dissociation constants (pKa values). Thus, a new spectrophotometric approach was elaborated for the pKa determination of these compounds, which is based on spectrophotometric titration in methanol with strong base and the titration results were evaluated by the Benesi-Hildebrand method. (In the studies with TEAOH, TMAOH and LiOMe, the complex formation between the ionophores and the cations of the bases could be excluded.) As it was expected, the experimentally determined pKa values depended on the nature of the substituents of the acridone moiety and pKa values ranged between 12.6 and 14.9. The lower pKa value of thioacridone compared to the acridone can be explained by the larger size of the sulfur atom. The outstandingly larger pKa value for 4,5-dinitroacridone can be attributed to the formation of intramolecular hydrogen-bonds between the ortho-position nitro group and the NH proton. As a trend, the strong electron withdrawing nitro substituents decreased considerably the pKa values of compounds and compared to that of the halogen (Cl and Br) atoms (for example compounds and) of weaker withdrawing effect.

Acridines↗
PubMed2003

Synthesis and biological activity of N-arylpiperazine-modified analogues of KN-62, a potent antagonist of the purinergic P2X7 receptor.

The P2X(7) receptor is involved in several processes relevant to inflammation (cytokine release, NO generation, killing of intracellular pathogens, cytotoxicity); thus, it may be an appealing target for pharmacological intervention. The characterization of native and recombinant P2X(7) receptor continues to be hindered by the lack of specific and subtype-selective antagonists. However, a tyrosine derivative named KN-62 exhibits selective P2X(7) receptor-blocking properties. The present study was designed to evaluate the functional antagonistic properties of a novel series of KN-62-related compounds characterized by the presence of different phenyl-substituted piperazine moieties. Antagonistic activity of KN-62 derivatives was tested on HEK293 cells transduced with the human P2X(7) receptor and monocyte-derived human macrophages, a cell type well-known for the high level of expression of this receptor. The biological responses investigated were ATP-dependent Ca(2+) influx across the plasma membrane, ethidium bromide uptake, and secretion of the cytokine interleukin-1beta. KN-62 was characterized by the presence of a phenylpiperazine moiety, and the presence of a one-carbon linker between the piperazine nitrogen and the phenyl ring (compound 61) increases the activity, while a two-carbon linker (compound 62) decreases biological activity 10-fold. Also, the nature and the position of substituents on the phenyl ring tethered to the piperazine seemed to exert a fundamental influence on the biological activity. In the series of synthesized compounds, the presence of a fluorine in the para position gives the most potent compound (63), while the same atom in the ortho position reduces potency by 3-fold. When the p-fluorine was replaced in the same position with other halogens, such as chlorine (compound 64) or iodine (compound 65), the activity decreased dramatically. We then tested the activity of the four most potent KN-62 derivatives on ATP-stimulated secretion of IL-1beta from monocyte-derived human macrophages, a key cell type in inflammation and innate immunity. Interestingly, compound 68 and 71 caused a complete inhibition of IL-1beta release, while with KN-62, 63, and 85, there was a small residual cytokine secretion even at concentrations exceeding 100 nM. None of the compounds tested on IL-1beta release had any effect on isolated CaMII kinase activity up to 20 microM (not shown).

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1996

Hypoxia-selective antitumor agents. 12. Nitrobenzyl quaternary salts as bioreductive prodrugs of the alkylating agent mechlorethamine.

A series of benzene-substituted analogues of the novel hypoxia-selective cytotoxin N,N-bis(2-chloroethyl)-N-methyl-N-(2-nitrobenzyl)ammonium chloride (3a), together with three corresponding tetrahydroisoquinolinium "cyclic" analogues 21a-23a and two naphthalene derivatives (19a and 20a), have been prepared and evaluated for cytotoxicity in cultured mammalian tumor cells under aerobic and hypoxic conditions. The parent compound 3a has a one-electron reduction potential of -358 mV and undergoes reductively-induced fragmentation to release the nitrogen mustard mechlorethamine. The compounds were prepared by halogenation (SOCl2) of the corresponding quaternary diols, which in turn were synthesized from N-methyldiethalnolamine and substituted nitrobenzyl chlorides. The reduction potentials of the benzene-substituted compounds were generally well-predicted by Hammett substituent relationships. All of the compounds were much more toxic toward repair-deficient UV4 cells than the corresponding wild-type AA8 cells, as expected if the active cytotoxic species as a DNA alkylating agent. They were also more toxic toward the human cell lines EMT6 and FME compared to AA8, but the reasons for this are not known. Analogues of 3a substituted in the phenyl ring with electron-donating substituents provided compounds with widely differing selectivities for hypoxic AA8 cells, ranging from no selectivity for the 3-Me compound 9a to 3000-fold (at least as great as that of the parent 3a) for the 4-OMe compound 14a. The naphthalene derivatives 19a and 20a and the tetrahydroisoquinolinium compounds 21a-23a showed no hypoxic selectivity. Selective chemical reduction of 22a and 23a with nickel boride resulted in isolation of the corresponding stable amino derivatives, indicating that reduction of these compounds does not result in fragmentation. The reason(s) for the marked differences in hypoxic selectivity of the nitrobenzyl quaternary mustards is unknown, but may reflect differences in radical chemistry, cell uptake, or sensitivity to enzymatic reduction.

Animals↗
PubMed2002

Synthesis of halogen-substituted pyridyl and pyrimidyl derivatives of [3,2-c]pyrazolo corticosteroids: strategies for the development of glucocorticoid receptor mediated imaging agents.

Ligands for the glucocorticoid receptor labeled with high-energy isotopes are highly desired for their potential applications in nuclear medical studies of the brain where the dysregulation of this receptor system is thought to be involved in various neurodegenerative disorders. Analogues of the glucocorticoid cortivazol have previously been prepared as target compounds for labeling with high-energy isotopes. However, the phenyl rings of arylpyrazoles of this type are not sufficiently activated for nucleophilic substitution reactions that are generally required for the synthesis of radiohalogenated analogues. Since suitably substituted aromatic nitrogen heterocyclic groups are amenable to nucleophilic substitution, the goal of this study was the synthesis of pyridylpyrazolo and pyrimidylpyrazolo analogues similar to cortivazol that could be labeled with radiohalogens in the pyridine or pyrimidine rings. We describe the synthesis of several [3,2-c]pyrazolo steroids containing pyridyl, halopyridyl, and pyrimidyl substituents at the 2' position of the pyrazole ring. These compounds were tested for binding to the glucocorticoid receptor and for biological activity in glucocorticoid responsive HeLa cells grown in tissue culture. Of the pyridyl and pyrimidyl derivatives, 2'-(3-pyridyl)-11 beta,17,21-trihydroxy-16 alpha-methyl-20-oxopregn-4-eno[3,2-c]pyrazole showed superior activity in both assays and it was used as the basis for the synthesis of several analogues that were halogenated in the pyridine ring. These halogenated compounds were all tested for their binding to the glucocorticoid receptor and for their biological activity. One, a fluorinated compound 2'-(2-fluoro-5-pyridyl)-11 beta,17,21-trihydroxy-16 alpha-methyl-20-oxopregn-4-eno[3,2-c]pyrazole had excellent activity, considerably better than the potent glucocorticoid dexamethasone. Most importantly, fluorination was achieved using a nucleophilic exchange reaction, a method that is adaptable to radiolabeling with the positron-emitting isotope fluorine-18. Thus, considering its superior biological activity and adaptability for facile radiosynthesis, this target compound has the potential for imaging of glucocorticoid receptor containing tissues using positron emission tomography.

Alkaline Phosphatase↗
PubMedDate not supplied

[The role of halogenation in the electro-oxidation of halogenated anilines in acetonitrile as the solvent].

The 4-halogeno-, 2,4-dihalogeno- and 2,4,6-trihalogenoanilines were the model substances of the research described. Acetonitrile being one of the most popular aprotic solvent was used. The halogeno monomers were chloro and bromoanilines. The electrodimerised substrate is stabilised by rejecting halogenide ion and protons. The rejected halogenide ions are oxidisable more easier compared to the substrate therefore the halogene formed substitutes both the substrate, and the dimer as well. The protons formed during the oxidation bind by the strong base monomer primary amine. Because of these not only a simple electrodimerisation will take place, but protonised monomers, higher halogenated monomers, and the corresponding dimer molecules are formed in the solution.

Acetonitriles↗
PubMed2006

Metabolism of mono- and dihalogenated C1 and C2 compounds by Xanthobacter autotrophicus growing on 1,2-dichloroethane.

The conversion of and toxic effects exerted by several mono- and dihalogenated C1 and C2 compounds on cultures of Xanthobacter autotrophicus GJ10 growing on 1,2-dichloroethane were investigated. Bromochloromethane, dibromomethane and 1-bromo-2-chloroethane were utilized by strain GJ10 in batch culture as a cosubstrate and sole carbon source. The rate of degradation of dihalomethanes by whole cells was lower than that of 1,2-dichloroethane, but a significant increase of the rate of dihalomethane biodegradation was observed when methanol or ethanol were added as a cosubstrate. Products of the degradation of several tested compounds by haloalkane dehalogenase were analyzed and a new metabolic pathway based on hydrolytic conversion to formaldehyde was proposed for the dihalomethanes. Strain GJ10 growing on 1,2-dichloroethane converted 2-fluoroethanol and 1-chloro-2-fluoroethane to 2-fluoroacetate, which was tolerated up to a concentration of 2.5 mM. On the basis of the results from batch cultures an inert (dichloromethane), a growth-supporting (dibromomethane) and a toxic (1,2-dibromoethane) compound were selected for testing their effects on a continuous culture of strain GJ10 growing on 1,2-dichloroethane. The compounds were added as pulses to a steady-state chemostat and the response of the culture was followed. The effects varied from a temporary decrease in cell density for dibromomethane to severe toxicity and culture washout with 1,2-dibromoethane. Our results extend the spectrum of halogenated C1 and C2 compounds that are known to be degraded by strain GJ10 and provide information on toxic effects and transformation of compounds not serving as a carbon source for this bacterium.

Culture Media↗
PubMed1993

Development of bioassays and approaches for the risk assessment of 2,3,7,8-tetrachlorodibenzo-p-dioxin and related compounds.

Polychlorinated biphenyls (PCBs), dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and related halogenated aromatic hydrocarbons (HAHs) are industrial compounds or by-products that have been identified as contaminants in almost every component of the global ecosystem. 2,3,7,8- Tetrachlorodibenzo-p-dioxin (TCDD) is the most toxic HAH, and studies in rodents have shown that this compound is a carcinogen. Analysis of environmental samples for HAHs has shown that these extracts contain complex mixtures of isomers and congeners, and this greatly complicates risk assessment due to the paucity of data available for most of the individual compounds. Extensive research has demonstrated a common receptor-mediated mechanism of action for TCDD and related toxic HAHs, and this has led to the development of a mechanism-based risk assessment approach for HAHs. Toxic equivalency factors (TEFs; relative potency compared to TCDD) have been developed for selected HAH congeners, and the TEF values can be used to determine "toxic equivalents" (TEQs) for HAH mixtures. In addition, several bioassays that use receptor-mediated end points have been developed and can be used directly to determine the TEQs for HAH mixtures. The applications of the TEF/TEQ approach for the risk assessment of HAHs are considerable, particularly with the conversion of complex analytical data into TEQs. However, there appear to be several limitations to this approach, particularly with PCBs because their potential nonadditive (antagonistic), interactive effects with "2,3,7,8-TCDD-like" compounds may invalidate the use of the risk assessment procedure for some environmental matrices.

Benzofurans↗
PubMed1994

New norepinephrine potentiators: synthesis and structure-activity relationships of a series of 4-phenyl-1,2,3,4-tetrahydroisoquinolin-4-ols.

A variety of 1,2,3,4-tetrahydroisoquinolin-4-ols (1-6) were prepared as part of our search for new norepinephrine (NE) potentiators and to clarify the structure-activity relationships. These compounds and some previously prepared compounds were compared with 2-methyl-4-phenyl-1,2,3,4-tetrahydroisoquinolin-4-ol (PI-OH) (1a) for ability to potentiate NE. The potency, for 2-substitution, was found to be in the order: Me > Et > iso-Pr > H. The compounds substituted by a halogen atom at the para position in the 4-phenyl group of PI-OH showed greater activities than did PI-OH, and the observed order of potency for the substitution was Cl > Br > F > H. The compound (4) methylated at the hydroxy group in PI-OH had greatly diminished activity. Although the desoxy compound (6) of PI-OH potentiated the response to NE at low concentrations, the potentiation was progressively masked by an inhibitory activity as the concentration of 6 was increased. In addition, the 4-cyclohexyl analogue (5) failed to potentiate NE. These results show the importance of the beta-phenylethanolamine skeleton of PI-OH for producing NE potentiation without accompanying inhibitory action. The racemic 4-chlorophenyl analogue (2a) was resolved by HPLC to (R)-(+)-2a and (S)-(-)-2a. The NE-potentiating activity was found to reside exclusively in (R)-(+)-2a, which had the highest activity among compounds tested in this study; the activity ratio was 25 at 3 x 10(-6) M. The antidepressant activity of racemic 2a was evaluated by a forced swimming test.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2000

Reduction of halogenated hydrocarbons in aqueous media: I. Involvement of sulfur in iron catalysis.

Experiments were carried out to investigate the reduction of tri- and tetra-chloroethene with iron in aqueous solutions. Results indicate (i) dependence of the dehalogenation capacity of the iron on its sulfur content and (ii) that ethyne was the primary dehalogenated hydrocarbon for both compounds. A reaction mechanism based on in situ formation of ferrous sulfide as the catalyst and its reaction with the halocompounds in the presence of hydrogen has been postulated.

Acetylene↗
PubMed1980

[Redoxpotential and germicidal action of aqueous halogen solution (author transl)].

Methods are given to calculate the equilibrium concentrations of both halogene solutions (chlorine, bromine and iodine) in the presence of additional halide and of chlorine solutions in the presence of chloride and ammonia. With the aid of these values and the redoxpotentials which have been determined from them is demonstrated that there is a very complicated connection between the latters and the total as well as the equilibrium concentrations. It depends on the kind of the halogene, the pH-value and the presence of substances which can react with the halogene (halides, NH-compounds) and can not be described by the simple formula: increase of the redoxpotential approximately increase of the equilibrium concentrations of germicidal hydrolysis products and as a consequence of the death rates. On the contrary a reduction of the total halogene concentration may cause an increase of the redoxpotential as well as the addition of halide may lower the redoxpotential while the concentration of strong germicidal "free halogene" remains unchanged. The redoxpotential therefore is not a mean to make reliable predictions concerning the germicidal action of halogene solutions.

Bromine↗
PubMed2003

Occupational exposure to fluorinated hydrocarbons during refrigeration repair work.

This study describes refrigeration repair workers' occupational exposures to halogenated refrigerants, focusing on difluorochloromethane (HCFC 22), tetrafluoroethane (HFC 134a) and a mixture of tri-, tetra- and pentafluoroethane (R404A) in 30 work operations. Unlike earlier reported studies, the present study includes working procedures involving welding in order to measure possible occupational exposure to decomposition products. The measurements included hydrogen fluoride (HF), hydrogen chloride (HCl), phosgene (COCl2) and volatile organic compounds (VOC). The exposures were assessed during work operations on small-scale cooling installations like refrigerators and freezers. The repair workers' occupational exposures to refrigerants were moderate, and the major part of the exposures were associated with specific working procedures lasting for relatively short periods of time (<20 min). During these exposure events the concentrations were occasionally high (up to 42434 mg m(-3)). Although welding operations lasted only for short periods of time, HF was detected in 9 out of 15 samples when HCFC 22, HFC 134a or R404A had been used. Hydrogen chloride was detected in 3 out of 5 samples in air polluted with HCFC 22. Phosgene was not detected. A large number of VOCs in various concentrations were found during welding. Except for the applied refrigerants, halogenated compounds were only found in one sample.

Adult↗
PubMed1999

Syntheses and biological activities of rebeccamycin analogues. Introduction of a halogenoacetyl substituent.

In the course of structure-activity relationships on rebeccamycin analogues, a series of compounds bearing a halogenoacetyl substituent were synthesized with the expectation of increasing the interaction with DNA, possibly via covalent reaction with the double helix. Two rebeccamycin analogues bearing an acetyl instead of a bromoacetyl substituent were prepared to gain an insight into the role of the halogen atom. The new compounds show very little effect on protein kinase C and no covalent reaction with DNA was detected. However, the drugs behave as typical topoisomerase I poisons, and they are significantly more toxic toward P388 leukemia cells than to P388/CPT5 cells resistant to camptothecin. The introduction of a bromo- or chloro-acetyl substituent does not affect the capacity of the drug to interfere with topoisomerase I either in vitro or in cells. One of the bromoacetyl derivatives, compound 8, is the most cytotoxic rebeccamycin derivative among the hundred of derivatives we have synthesized to date. In addition, we determined the antimicrobial activities against two Gram-positive bacteria, Bacillus cereus and Streptomyces chartreusis, and against the Gram-negative bacterium Escherichia coli. The effect of the drugs on Candida albicans yeast growth and their anti-HIV-1 activities were also measured.

Aminoglycosides↗
PubMed1989

Studies on heterocyclic compounds: 1,3-thiazolidin-4-one derivatives. III. Biological activity of halogenated 2,3-diaryl-1,3-thiazolidin-4-ones.

In previous communications from these laboratories, thiazolidinone derivatives of general formula (A) were synthesized and screened for antimicrobial activity. (formula; see text) where: X = H, CH3 Ar = phenyl Ar' = fluorinated or chlorinated phenyl The present communication is in part concerned with further extension of these studies to variously halogenated thiazolidinones of general formula (B). (formula; see text) where: X = H, CH3 R = H, 2-F, 3-F, 4-F, 3-Cl, 4-Cl R' = H, 4-F, 4-Cl These compounds were prepared by the general synthetic procedure previously reported for the 1,3-thiazolidin-4-one derivatives already prepared and screened in this SARs program. The general synthetic approach involves the cyclocondensation of the appropriate Schiff bases with alpha-mercaptoalkanoic acids such as thioglycolic and thiolactic acid. The prepared compounds were tested for their possible activity by a disk-diffusion assay (Kirby-Bauer modified). The organisms used were: S. aureus, S. beta-haemoliticus, B. subtilis, M. paratuberculosis 607, S. typhi, Kl. pneumoniae, E. coli Bb, Ps. aeruginosa, C. albicans, A. niger, S. cerevisiae. The results of this antimicrobial screening showed that the prepared compounds exhibited varying degrees of activity against Gram-positive, Gram-negative bacteria, and fungi. The second half of this report deals with the structure-activity relationships in all the compounds prepared and studied in this research program. For comparison of antimicrobial activity, the growth inhibitory activity of all the halogenated thiazolidinones of type (A) and (B), prepared and screened in this SARs study, were tabulated.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteria↗