Development of 3,5-Dinitrophenyl-Containing 1,2,4-Triazoles and Their Trifluoromethyl Analogues as Highly Efficient Antitubercular Agents Inhibiting Decaprenylphosphoryl-ß-d-ribofuranose 2'-Oxidase.

We report herein the discovery of 3,5-dinitrophenyl 1,2,4-triazoles with excellent and selective antimycobacterial activities against Mycobacterium tuberculosis strains, including clinically isolated multidrug-resistant strains. Thorough structure-activity relationship studies of 3,5-dinitrophenyl-containing 1,2,4-triazoles and their trifluoromethyl analogues revealed the key role of the position of the 3,5-dinitrophenyl fragment in the antitubercular efficiency. Among the prepared compounds, the highest in vitro antimycobacterial activities against M. tuberculosis H37Rv and against seven clinically isolated multidrug-resistant strains of M. tuberculosis were found with S-substituted 4-alkyl-5-(3,5-dinitrophenyl)-4H-1,2,4-triazole-3-thiols and their 3-nitro-5-(trifluoromethyl)phenyl analogues. The minimum inhibitory concentrations of these compounds reached 0.03 µM, which is superior to all the current first-line anti-tuberculosis drugs. Furthermore, almost all compounds with excellent antimycobacterial activities exhibited very low in vitro cytotoxicities against two proliferating mammalian cell lines. The docking study indicated that these compounds acted as the inhibitors of decaprenylphosphoryl-ß-d-ribofuranose 2'-oxidase enzyme, which was experimentally confirmed by two independent radiolabeling experiments.

Cell surface clicking of antibody-recruiting polymers to metabolically azide-labeled cancer cells.

Triggering antibody-mediated innate immune mechanisms to kill cancer cells is an attractive therapeutic avenue. In this context, recruitment of endogenous antibodies to the cancer cell surface could be a viable alternative to the use of monoclonal antibodies. We report on antibody-recruiting polymers containing multiple antibody-binding hapten motifs and cyclooctynes that can covalently conjugate to azides introduced onto the glycocalyx of cancer cells by metabolic labeling with azido sugars.

Inhibition of C. albicans Dimorphic Switch by Cobalt(II) Complexes with Ligands Derived from Pyrazoles and Dinitrobenzoate: Synthesis, Characterization and Biological Activity.

Seven cobalt(II) complexes of pyrazole derivatives and dinitrobenzoate ligands were synthesized and characterized. The single-crystal X-ray diffraction structure was determined for one of the ligands and one of the complexes. The analysis and spectral data showed that all the cobalt complexes had octahedral geometries, which was supported by DFT calculations. The complexes and their free ligands were evaluated against fungal strains of Candida albicans and emerging non-albicans species and epimastigotes of Trypanosoma cruzi. We obtained antifungal activity with a minimum inhibitory concentration (MIC) ranging from 31.3 to 250 µg mL-1. The complexes were more active against C. krusei, showing MIC values between 31.25 and 62.5 µg mL-1. In addition, some ligands (L1-L6) and complexes (5 and Co(OAc)2 · 4H2O) significantly reduced the yeast to hypha transition of C. albicans at 500 µg mL-1 (inhibition ranging from 30 to 54%). Finally, the complexes and ligands did not present trypanocidal activity and were not toxic to Vero cells. Our results suggest that complexes of cobalt(II) with ligands derived from pyrazoles and dinitrobenzoate may be an attractive alternative for the treatment of diseases caused by fungi, especially because they target one of the most important virulence factors of C. albicans.

A Triple-Emission Fluorescent Probe for Discriminatory Detection of Cysteine/Homocysteine, Glutathione/Hydrogen Sulfide, and Thiophenol in Living Cells.

Thiols, such as cysteine (Cys), homocysteine (Hcy), glutathione (GSH), hydrogen sulfide (H2S), and thiophenol are metabolically correlated with each other via redox reactions. As a result of the similarity of chemical properties between Cys, Hcy, GSH, H2S, and thiophenol, it is very challenging to develop an effective methodology to differentiate them. In this work, a triple-emission fluorescent probe, NCQ, was reported for the simultaneous detection of Cys/Hcy, GSH/H2S, and thiophenol with high sensitivity and selectivity. The solution of NCQ displayed distinct fluorescent signals toward Cys/Hcy, GSH/H2S, and thiophenol: blue and green for Cys/Hcy, blue for GSH/H2S, blue and red for thiophenol. Through the blue-green-red emission color combination, Cys/Hcy, GSH/H2S, and thiophenol could be discriminatively detected in solution and in living cells.

Development of cyanine probes with dinitrobenzene quencher for rapid fluorogenic protein labelling.

A multicolour protein labelling technique using a protein tag and fluorogenic probes is a powerful approach for spatio-temporal analyses of proteins in living cells. Since cyanine fluorophores have attractive properties for multicolour imaging of proteins, there is a huge demand to develop fluorogenic cyanine probes for specific protein labelling in living cells. Herein, we develop fluorogenic cyanine probes for labelling a protein tag by using a dinitrobenzene fluorescence quencher. The probes enhanced fluorescence intensity upon labelling reactions and emitted orange or far-red fluorescence. Intramolecular interactions between the cyanine fluorophores and the dinitrobenzene quencher led not only to fluorescence quenching of the probes in the free state but also to promotion of labelling reactions. Furthermore, the probes successfully imaged cell-surface proteins without a washing process. These findings offer valuable information on the design of fluorogenic cyanine probes and indicate that the probes are useful as novel live-cell imaging tools.This article is part of the themed issue 'Challenges for chemistry in molecular imaging'.

A highly selective and sensitive near-infrared fluorescent probe for imaging of hydrogen sulphide in living cells and mice.

Hydrogen sulphide (H2S), the third endogenous gaseous signalling molecule, has attracted attention in biochemical research. The selective detection of H2S in living systems is essential for studying its functions. Fluorescence detection methods have become useful tools to explore the physiological roles of H2S because of their real-time and non-destructive characteristics. Herein we report a near-infrared fluorescent probe, NIR-HS, capable of tracking H2S in living organisms. With high sensitivity, good selectivity and low cytotoxicity, NIR-HS was able to recognize both the exogenous and endogenous H2S in living cells. More importantly, it realized the visualization of endogenous H2S generated in cells overexpressing cystathionine ß-synthase (CBS), one of the enzymes responsible for producing endogenous H2S. The probe was also successfully applied to detect both the exogenous and endogenous H2S in living mice. The superior sensing properties of the probe render it a valuable research tool in the H2S-related medical research.

Synthesis, characterization, biological evaluation and docking studies of macrocyclic binuclear manganese(II) complexes containing 3,5-dinitrobenzoyl pendant arms.

A series of bis(phenoxo) bridged binuclear manganese(II) complexes of the type [Mn2L(1-3)](ClO4)2 (1-3) containing 3,5-dinitrobenzoyl pendant-arms have been synthesized by cyclocondensation of 2,6-diformyl-4-R-phenols (where R=CH3, C(CH3)3 or Br) with 2,2'-3,5-dinitrobenzoyliminodi(ethylamine) trihydrochloride in the presence of manganese(II) perchlorate. The IR spectra of complexes indicate the presence of uncoordinated perchlorate anions. The UV-Vis spectra of complexes suggest the distorted octahedral geometry around manganese(II) nuclei. The EPR spectra of Mn(II) complexes show a broad signal with g value 2.03-2.04, which is characteristic for octahedral high spin Mn(2+) complex. The observed room temperature magnetic moment values of the Mn(II) complexes (5.60-5.62B.M.) are less than the normal value (5.92B.M.), indicating weak antiferromagnetic coupling interaction between the two metal ions. Electrochemical studies of the complexes show two distinct quasi-reversible one electron transfer processes in the cathodic (E(1)pc=-0.73 to -0.76V, E(2)pc=-1.30 to -1.36V), and anodic (E(1)pa=1.02-1.11V, E(2)pa=1.32-1.79V) potential regions. Antibacterial efficacy of complexes have been screened against four Gram (-ve) and two Gram (+ve) bacterial strains. The DNA interaction studies suggest that these complexes bind with CT-DNA by intercalation, giving the binding affinity in the order 1>2>3. All the complexes display significant cleavage activity against circular plasmid pBR322 DNA. Docking simulation was performed to insert complexes into the crystal structure of EGFR tyrosine kinase and B-DNA at active site to determine the probable binding mode.

Synthesis and determination of some biological activities of novel 2,4-dinitrophenyl derivatives.

The antioxidant and radical scavenging activities of the synthesized compounds 3, 5, and 6 were determined by various in vitro assays such as 2,2-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid radical (ABTS(·+) ) scavenging, ferric ion (Fe(3+) ) reducing power and ferrous ion (Fe(2+) ) chelating activities. Moreover, these activities were compared to those of standard antioxidants such as butylated hydroxyanisole, butylated hydroxytoluene, and trolox. The results showed that the new compounds (3, 5, and 6) had potential antioxidant activity. Besides, inhibition of the two human cytosolic carbonic anhydrase (hCA, EC 4.2.1.1) isozymes I and II with some nitrobenzene compounds was investigated. Compounds 1-6 showed Ki values in the range of 4.88-193.4 µM and 5.295-54.75 µM for hCA I and hCA II, respectively.

Accessing lipophilic ligands in dendrimer-based amphiphilic supramolecular assemblies for protein-induced disassembly.

Supramolecular nanoassemblies that respond to the presence of proteins are of great interest, as aberrations in protein concentrations represent the primary imbalances found in a diseased state. We present here a molecular design, syntheses, and study of facially amphiphilic dendrimers that respond to the presence of the protein, immunoglobulin G. It is of particular interest that the ligand functionality, utilized for causing the binding-induced disassembly, be lipophilic. Demonstration of binding with lipophilic ligands greatly expands the repertoire of binding-induced disassembly, since this covers a rather large class of ligand moieties designed for proteins and these provide specific insights into the mechanistic pathways that are available for the binding-induced disassembly process. Here, we describe the details of the binding induced disassembly, including the change in size of the assembly in response to proteins, concurrent release of noncovalently encapsulated guest molecules, and the specificity of the disassembly process.

Evolution of catabolic pathways and their regulatory systems in synthetic nitroaromatic compounds degrading bacteria.

Evolution of catabolic pathways for the degradation of synthetic nitroaromatic compounds is currently ongoing process because these compounds have been in nature only for a short time. Bacteria isolated from contaminated areas contain pathways for the degradation of nitroaromatic compounds at different stages of progression. Therefore, the emergence of pathways for the degradation of such chemicals provides a good opportunity to investigate evolutionary processes leading to the emergence of new metabolic routes and their regulatory systems. In Burkholderia sp. strain DNT the regulatory gene encoding the LysR-type transcriptional regulator DntR is placed divergently of the dinitrotoluene (DNT) dioxygenase genes. This regulator still recognizes salicylate, an effector of its NagR-like ancestor but not DNT. In this issue of Molecular Microbiology, de las Heras et al. demonstrate that the DntR does not respond to any metabolic intermediates of the DNT catabolic pathway. The results of this study suggest that the catabolic pathway for the degradation of DNT has reached to an early stage of evolution when novel specificities of the catabolic enzymes have already acquired but the cognate regulatory system is still missing. This research addresses some fundamental questions about bottlenecks to be solved during evolution of new catabolic operons.

Design, synthesis and biological evaluation of novel nitroaromatic compounds as potent glutathione reductase inhibitors.

Discovery of GR inhibitors has become very popular recently due to antimalarial and anticancer activities. In this study, the synthesis and GR inhibitory capacities of novel nitroaromatic compounds (NCs) (1-3) were reported. Some commercially available molecules were also tested for comparison reasons. The novel NCs were obtained in high yields using simple chemical procedures and exhibited much potent inhibitory activities against GR at low micromolar concentrations with K(i) values ranging from 0.211 to 4.57 µM as compared with well-known agents. Inhibition mechanism was assessed as being due to occlusion of the active site entrance by means of the NCs. Molecular docking results have shown that docking poses of ligands are able to construct binding interactions with the essential amino acids.

A selective fluoride encapsulated neutral tripodal receptor capsule: solvatochromism and solvatomorphism.

The dinitrophenyl functionalized tris-(amide) receptor behaves as a selective chemosensor for fluoride by encapsulation within the tripodal pseudocavity in polar aprotic solvents exhibiting solvatochromism and solvatomorphism.

Cancer of the urinary bladder in highly exposed workers in the production of dinitrotoluenes: a case report.

Technical dinitrotoluene (consisting of 2,4- and 2,6-dinitrotoluene isomers) has been widely used as explosives. Both technical isomers are mutagenic in Salmonella typhimurium TA98 strains and carcinogenic in rodents. 2,4-dinitrotoluene shows a dose-dependency of malignant tumors of the kidneys, liver, and mammary glands in rats and mice. In this case report, we discuss a cluster of three cases of urothelial cancer amongst a group of about 60 workers exposed to dinitrotoluenes. The workers were employed in the manufacturing of nitrotoluene explosives in the former German Democratic Republic. The cases occurred within a period of 12 years (1990-2002) leading to a 15.9 fold higher incidence of cancer of the urinary bladder than of the federal state where the chemical factory was located. The observation of the cluster of urothelial cancer in persons highly exposed to nitrotoluenes underlines the putative human carcinogenicity of dinitrotoluenes with the human urothelium as a relevant target tissue.

Marfey's reagent for chiral amino acid analysis: a review.

The present paper describes characteristics and application of Marfey's reagent (MR) including general protocols for synthesis of the reagent and diastereomers along with advantages, disadvantages and the required precautions. Applications, and comparison with other derivatizing agents, for the resolution of complex mixtures of DL-amino acids, amines and non-proteinogenic amino acids, peptides/amino acids from microorganisms, cysteine residues in peptides, and evaluation of racemizing characteristics have been discussed. Separation mechanisms of resolution of amino acid diastereomers and replacement of Ala-NH2 by suitable chiral moieties providing structural analogs and different chiral variants and their application as a derivatizing agent to examine the efficiency, and reactivity of the reagent have been focussed. Use of MR for preparing CSPs for direct enantiomeric resolution has also been included.

Highly effective poly(ethylene glycol) architectures for specific inhibition of immune receptor activation.

Architectural features of synthetic ligands were systematically varied to optimize inhibition of mast cell degranulation initiated by multivalent crossing of IgE-receptor complexes. A series of ligands were generated by end-capping poly(ethylene glycol) (PEG) polymers and amine-based dendrimers with the hapten 2,4-dinitrophenyl (DNP). These were used to explore the influence of polymeric backbone length, valency, and hapten presentation on binding to anti-DNP IgE and inhibition of stimulated activation of RBL cells. Monovalent MPEG(5000)-DNP (IC(50) = 50 nM), bivalent DNP-PEG(3350)-DNP (IC(50) = 8 nM), bismonovalent MPEG(5000)-DNP(2) (IC(50) = 20 nM), bisbivalent DNP(2)-PEG(3350)-DNP(2) (IC(50) = 3nM) and DNP(4)-dendrimer ligands (IC(50) = 50 nM) all effectively inhibit cellular activation caused by multivalent antigen, DNP-bovine serum albumin. For different DNP ligands, we provide evidence for more effective inhibition due to (i) preferential formation of intra-IgE cross-links by bivalent ligands of sufficient length, (ii) self-association of monovalent ligands with longer tails, and (iii) higher probability of binding for bisvalent ligands. We also show that larger DNP(16)-dendrimers of higher valency trigger degranulation by cross-linking IgE-receptor complexes, whereas smaller DNP-dendrimers are inhibitory. Thus, features of synthetic ligands can be manipulated to control receptor occupation, aggregation, and inhibition of the cellular response.

Cost-effective synthesis of 5,7-diamino-4,6-dinitrobenzofuroxan (CL-14) and its evaluation in plastic bonded explosives.

5,7-Diamino-4,6-dinitrobenzofuroxan (CL-14) has been synthesized by a cost-effective method. CL-14 was characterized by spectral data (IR, NMR and mass) and elemental analysis. The compound was evaluated in plastic bonded explosives (PBX) using polyurethane (PU) as binder. The thermal, mechanical and explosive properties of PBX composition from preliminary tests are also reported. Good thermal stability as well as good insensitiveness are indicated.

Synthesis of S6-(2,4-dinitrophenyl)-6-thioguanosine phosphoramidite and its incorporation into oligoribonucleotides.

The preparation of N(2)-phenoxylacetyl-S(6)-(2,4-dinitrophenyl)-6-thioguanosine phosphoramidite and its subsequent incorporation into oligoribonucleotides is described. The identity of the oligonucleotides was confirmed by UV spectrophotometry and nucleoside composition analysis.

Synthesis, characterisation, thermal and explosive properties of 4,6-dinitrobenzofuroxan salts.

Two new initiatory molecules, e.g. rubidium and cesium salts of 4,6-dinitrobenzofuroxan (DNBF) have been prepared by reacting sodium salt of 4,6-dinitrobenzofuroxan (DNBF) with rubidium nitrate and cesium nitrate, respectively, at 60 degrees C in aqueous medium. The characterisation of compounds by IR, (1)H-NMR, elemental analysis and metal content is described along with some of the evaluated thermal and explosive properties. The results indicate that cesium salt of DNBF (Cs-DNBF) appears promising initiatory and may suitably replace potassium salt of DNBF (K-DNBF), being used currently in initiatory compositions.

Solution-phase synthesis of a 1,5-dialkylamino-2,4-dinitrobenzene library and the identification of novel antibacterial compounds from this library.

In this report we demonstrate that a 1,5-dialkylamino-2,4-dinitrobenzene small molecule library can be generated by a highly efficient solution-phase synthesis method. From this 2485-member library, a series of novel compounds with antibacterial activity were isolated. The significance of this report is that the synthetic scheme is extremely simple, with minimal number of liquid handling steps, and the solvents and reagents left in the final library preparation are fully compatible with cell-based assays.

Synthesis and evaluation of dinitroanilines for treatment of cryptosporidiosis.

The efficacy of a series of dinitroaniline herbicide derivatives for the treatment of Cryptosporidium parvum infections has been studied. The lead compounds oryzalin (compound 1) and trifluralin (compound 2) have low water solubility (<3 ppm) which was alleged to be a major contributor to their poor pharmacokinetic availability. Derivatives of compounds 1 and 2 were synthesized. In these derivatives the functionality at the C-1 amine position or the C-4 position was substituted with groups with various hydrophilicities to determine if a direct relation existed between water solubility and overall activity. The chlorinated precursors of these derivatives were also examined and were found to be less active in the C. parvum assays, a result in direct contrast to earlier work with Leishmania. Enhanced water solubility alone did not overcome the drug availability problem; however, several candidates with similar activities but with toxicities lower than those of the lead compounds were produced.