Toxizität chlororganischer Verbindungen: Einfluß der Einführung von Chlor in organische Moleküle

Antibacterial and Antibiofilm Activities of Chloroindoles Against Vibrio parahaemolyticus

Vibrio parahaemolyticus is a food-borne pathogen recognized as the prominent cause of seafood-borne gastroenteritis globally, necessitating novel therapeutic strategies. This study examined the antimicrobial and antivirulence properties of indole and 16 halogenated indoles on V. parahaemolyticus. Among them, 4-chloroindole, 7-chloroindole, 4-iodoindole, and 7-iodoindole effectively inhibited planktonic cell growth, biofilm formation, bacterial motility, fimbrial activity, hydrophobicity, protease activity, and indole production. Specifically, 4-chloroindole at 20 μg/mL inhibited more than 80% of biofilm formation with a minimum inhibitory concentration (MIC) of 50 μg/mL against V. parahaemolyticus and Vibrio harveyi. In contrast, 7-chloroindole inhibited biofilm formation without affecting planktonic cell growth with a MIC of 200 μg/mL. Both chlorinated indoles caused visible damage to the cell membrane, and 4-chloroindole at 100 μg/mL had a bactericidal effect on V. parahaemolyticus within 30 min treatment, which is superior to the effect of tetracycline at the same dose. The quantitative structure-activity relationship (QSAR) analyses revealed that chloro and bromo at positions 4 or 5 of the indole are essential for eradicating the growth of V. parahaemolyticus. These results suggest that halogenated indoles have potential use in antimicrobial and antivirulence strategies against Vibrio species.

Synthetic approaches and pharmaceutical applications of chloro-containing molecules for drug discovery: A critical review

At present more than 250 FDA approved chlorine containing drugs were available in the market and many pharmaceutically important drug candidates in pre-clinical trials. Thus, it is quite obvious to expect that in coming decades there will be an even greater number of new chlorine-containing pharmaceuticals in market. Chlorinated compounds represent the family of compounds promising for use in medicinal chemistry. This review describes the recent advances in the synthesis of chlorine containing heterocyclic compounds as diverse biological agents and drugs in the pharmaceutical industries for the inspiration of the discovery and development of more potent and effective chlorinated drugs against numerous death-causing diseases.

Environmental occurrence of Q1, a C9H3C17N2 compound, that has been identified as a natural bioaccumulative organochlorine

Environmental appearance of Q1, a natural heptachloro compound with the molecular formula C9H3C17N2, was studied in samples from different sites all over the world. Q1 was expected to have a bipyrrole backbone, similar to other compounds ascribed to natural sources. A method for isolation of Q1 was developed by combination of adsorption chromatography on silica and normal phase HPLC with an amino phase. UV-detection of Q1 supports the aromatic character of the compound. The high levels detected in samples of marine mammals and birds suggested that Q1 is both a persistent and a bioaccumulative contaminant. This was underscored by calculated logK(ow) in the range of other lipophilic organohalogens. In accordance with earlier studies, highest Ql concentrations were found in the Southern Hemisphere, but with a highly selective GC/ECNI-MS-SIM method, detection of Q1 was also achieved in many samples from the Northern Hemisphere. In addition to marine mammals and birds. Q1 was also detected in fish from the Mediterranean Sea and the Antarctic. Traces were also detected in SRM 1588 certified cod liver oil, but Q1 was not detected in fish from Hong Kong and Lake Baikal.

Determination of Q1, an unknown organochlorine contaminant, in human milk, Antarctic air, and further environmental samples

Q1, an organochlorine component with the molecular formula C(9)H(3)Cl(7)N(2) and of unknown origin was recently identified in seal blubber samples from the Namibian coast (southwest of Africa) and the Antarctic. In these samples, Q1 was more abundant than PCBs and on the level of DDT residues. Furthermore, Q1 was more abundant in seals from the Antarctic than the Arctic. To prove this assumption, gas chromatography-electron-capture negative ion mass spectrometry (GC/ECNI-MS), which is sensitive and selective for Q1, allowed for screening of traces of Q1 even in samples with particularly high levels of other organochlorine contaminants. Q1 was isolated by high-performance liquid chromatography (HPLC) from a skua liver sample. A 1:1 mixture with trans-nonachlor in electron-capture detectors (ECDs) was used to determine the relative response factor with ECNI-MS. The ECNI-MS response of Q1 turned out to be 4.5 times higher than that of trans-nonachlor in an ECD. With GC/ECNI-MS in the selected ion-monitoring mode, four Antarctic and four Arctic air samples were investigated for the presence of Q1. In the Antarctic air samples, Q1 levels ranged from 0.7 to 0.9 fg/m(3). In Arctic air samples, however, Q1 was below the detection limit (<0.06 fg/m(3) or 60 ag/m(3)). We also report on high Q1 levels in selected human milk samples (12-230 microg/kg lipid) and, therefore, suggested that the unknown Q1 is an environmental compound whose origin and distribution should be investigated in detail. Our data confirm that Q1 is a bioaccumulative natural organochlorine product. Detection of a highly chlorinated natural organochlorine compound in air and human milk is novel.

Mass spectrometric characterization of Q1, a C(9)H(3)Cl(7)N(2) contaminant in environmental samples

Q1, a heptachloro component of unknown structure and origin, was recently identified as a major organochlorine contaminant in samples from Africa and the Antarctic. Gas chromatography in combination with low resolution mass spectrometry (LRMS) was applied to establish a molecular weight of m/z 384 including seven chlorine atoms. Three possible molecular formulae (C(11)H(7)Cl(7), C(10)H(3)Cl(7)O, and C(9)H(3)Cl(7)N(2)) were proposed which could not be distinguished by LRMS. In this presentation the molecular composition of Q1 was studied using gas chromatography in combination with high resolution electron impact ionization mass spectrometry. With the option of further heteroatoms (P, S, N, O, F, and Br), 17 molecular formulae were obtained for the molecular weight of 384 u. In the selected ion monitoring (SIM) mode, performed with a resolution of 16,000, highest response was found at 383.812 or C(9)H(3)Cl(7)N(2). 11 fragment ions detected in the low resolution full scan mass spectrum of Q1 were also investigated in the high resolution SIM mode. In every case, the nitrogen-variant showed highest abundance while the other 16 structural variants could be definitely excluded. These investigations revealed that the molecular formula of Q1 is C(9)H(3)Cl(7)N(2). No stable component with this molecular formula has ever been reported in the literature, to our knowledge. Copyright 1999 John Wiley & Sons, Ltd.

Construction and use of an ipb DNA module to generate Pseudomonas strains with constitutive trichloroethene and isopropylbenzene oxidation activity

Pseudomonas sp. strain JR1 exhibits trichloroethene (TCE) oxidation activity with isopropylbenzene (IPB) as the inducer substrate. We previously reported the genes encoding the first three enzymes of the IPB-degradative pathway (ipbA1, ipbA2, ipbA3, ipbA4, ipbB, and ipbC) and identified the initial IPB dioxygenase (IpbA1 A2A3A4) as responsible for TCE cooxidation (U. Pflugmacher, B. Averhoff, and G. Gottschalk, Appl. Environ. Microbiol. 62:3967-3977, 1996). Primer extension analyses revealed multiple transcriptional start points located upstream of the translational initiation codon of ipbA1. The transcription from these start sites was found to be IPB dependent. Thirty-one base pairs upstream of the first transcriptional start point tandemly repeated DNA sequences overlapping the -35 region of a putative sigma 70 promoter were found. These repeats exhibit significant sequence similarity to the operator-promoter region of the xyl meta operon in Pseudomonas putida, which is required for the binding of XylS, a regulatory protein of the XylS (also called AraC) family. These similarities suggest that the transcription of the IPB dioxygenase genes is modulated by a regulatory protein of the XylS/AraC family. The construction of an ipb DNA module devoid of this ipb operator-promoter region and the stable insertion of this DNA module into the genomes of different Pseudomonas strains resulted in pseudomonads with constitutive IPB and TCE oxidation activities. Constitutive TCE oxidation of two such Pseudomonas hybrid strains, JR1A::ipb and CBS-3::ipb, was found to be stable for more than 120 generations in antibiotic-free medium. Evaluation of constitutive TCE degradation rates revealed that continuous cultivation of strain JR1A::ipb resulted in a significant increase in rates of TCE degradation.

Reactivity of haloketenes and halothioketenes with nucleobases: chemical characterization of reaction products

Halothioketenes and haloketenes are postulated as intermediates in haloolefin bioactivation. Little is known about the interactions of these reactive intermediates with macromolecules such as DNA. DNA binding, however, may be relevant in the toxicity of the parent olefins since they or their proximate metabolites are genotoxic. This prompted us to elucidate the structures and properties of potential DNA adducts formed. Adenine, cytosine, guanine, and thymine were reacted with chloro- and dichlorothioketene, chloro- and dichloroketene, and chloro- and dichloroacyl chloride. While thymine did not react, adenine and cytosine formed stable DNA base adducts with all reaction partners as demonstrated by HPLC analysis. Guanine yielded only products with chloroketene and chloroacetyl chloride. The pH-dependent UV spectra, 1H and 13C NMR, FT-IR, and elemental analysis showed (i) nucleophilic attack of the exocyclic amino groups of the DNA bases yielded haloacyl (thio)amides with all reactants as clearly demonstrated by the FT-IR spectra; (ii) the sulfur in the initial thioamides seems to be rapidly exchanged with oxygen; (iii) the acyl chlorides form identical products but in lower yields as compared to the haloketenes. Reactions of the nucleosides with haloketenes showed the formation of similar nucleoside adducts upon HPLC and MS analysis. Beside the modification of the base moieties, additional peaks in the reaction mixtures analyzed suggested acylation of the deoxyribose hydroxyl groups. In aqueous solutions at pH 7 N6-(chloroacetyl)adenine, N4-(chloroacetyl)cytosine, and N2-(chloroacetyl)guanine are not stable and cleaved to the original base or form 1,N6-acetyladenine, 3,N4-acetylcytosine, 1,N2-acetylguanine, and N2,3-acetylguanine. Under the same conditions, N6-(dichloroacetyl)adenine and N4-(dichloroacetyl)cytosine were completely hydrolyzed to adenine and cytosine, respectively. All haloacyl DNA base adducts proved to be stable at pH 5 but were rapidly degraded at neutral or alkaline pH. The compounds with an additional five-membered ring remained unchanged after 1 week at room temperature. All synthesized DNA base adducts except N2-(chloroacetyl)guanine and 1,N2-acetylguanine were fluorescent. The characterized compounds, especially the etheno (epsilon) base adduct-related derivatives, may represent potential DNA adducts formed as a consequence of haloolefin bioactivation.