Synthesis, X-ray crystal structure, antimicrobial activity and photodynamic effects of some thiabendazole complexes

Green Approach Toward Triazole Forming Reactions for Developing Anticancer Drugs

Compounds containing triazole have many significant applications in the dye and ink industry, corrosion inhibitors, polymers, and pharmaceutical industries. These compounds possess many antimicrobial, antioxidant, anticancer, antiviral, anti-HIV, antitubercular, and anticancer activities. Several synthetic methods have been reported for reducing time, minimizing synthetic steps, and utilizing less hazardous and toxic solvents and reagents to improve the yield of triazoles and their analogues synthesis. Among the improvement in methods, green approaches towards triazole forming biologically active compounds, especially anticancer compounds, would be very important for pharmaceutical industries as well as global research community. In this article, we have reviewed the last five years of green chemistry approaches on click reaction between alkyl azide and alkynes to install 1,2,3-triazole moiety in natural products and synthetic drug-like molecules, such as in colchicine, flavanone cardanol, bisphosphonates, thiabendazoles, piperazine, prostanoid, flavonoid, quinoxalines, C-azanucleoside, dibenzylamine, and aryl-azotriazole. The cytotoxicity of triazole hybrid analogues was evaluated against a panel of cancer cell lines, including multidrug-resistant cell lines.

Review of Characteristics and Analytical Methods for Determination of Thiabendazole

Thiabendazole (TBZ) is a fungicide and anthelmintic drug commonly found in food products. Due to its toxicity and potential carcinogenicity, its determination in various samples is important for public health. Different analytical methods can be used to determine the presence and concentration of TBZ in samples. Liquid chromatography (LC) and its subtypes, high-performance liquid chromatography (HPLC) and ultra-high-performance liquid chromatography (UHPLC), are the most commonly used methods for TBZ determination representing 19%, 18%, and 18% of the described methods, respectively. Surface-enhanced Raman spectroscopy (SERS) and fluorimetry are two more methods widely used for TBZ determination, representing 13% and 12% of the described methods, respectively. In this review, a number of methods for TBZ determination are described, but due to their limitations, there is a high potential for the further improvement and development of each method in order to obtain a simple, precise, and accurate method that can be used for routine analysis.

Investigating Structural Property Relationships to Enable Repurposing of Pharmaceuticals as Zinc Ionophores

The importance of zinc in biology has gained greater recognition in recent years due to its essential contributions to the function of many endogenous enzymes. Disruption of zinc homeostasis may be useful in treating pathological conditions, such as Alzheimer's, and for antiviral purposes. Despite the growth of knowledge and increased interest in zinc, little is known about the structure and function of zinc ionophores. In this study we analyse the Cambridge Structural Database and solution complexation studies found in the literature to identify key functional groups which may confer zinc ionophorism. Pharmaceuticals, nutraceuticals and amino acids with these functionalities were selected to enable us to explore the translatability of ionophoric activity from in vitro assays to cellular systems. We find that although certain species may complex to zinc in the solid and solution states, and may carry ions across simple membrane systems, this does not necessarily translate into ionophoric activity. We propose that the CSD can help refine key functionalities but that ionophoric activity must be confirmed in cellular systems.

Synthesis, characterization and in vitro anticancer activity of thiabendazole-derived 1,2,3-triazole derivatives

Thiabendazolium salts with 1,2,3-triazole motifs were synthesized and characterized; they exhibit good cytotoxic activity.

Cu(II)-dipeptide complexes of 2-(4'-thiazolyl)benzimidazole: synthesis, DNA oxidative damage, antioxidant and in vitro antitumor activity

Two new Cu(II)-dipeptide complexes of 2-(4'-thiazolyl)benzimidazole, [Cu(Gly-Gly)(TBZ)(Cl)]·4H2O (1) and [Cu(Gly-l-Leu)(TBZ)(Cl)]·H2O (2) (Gly-Gly=glycyl-glycine anion, Gly-l-Leu=glycyl-l-leucine anion and TBZ=2-(4'-thiazolyl)benzimidazole) have been synthesized and characterized by elemental analyses, molar conductance measurements and spectroscopy methods (IR, UV-visible, electrospray ionization mass spectra (ESI-MS) and EPR). The DNA binding and cleavage properties of the complexes monitored by multi-spectroscopic techniques (UV absorption, fluorescence and circular dichroism), viscosity determination and agarose gel electrophoresis indicated that the complexes bound to calf thymus (CT)-DNA via a partial intercalative mode with considerable intrinsic binding constants (Kb=1.64×10(5)M(-1) for 1 and 2.59×10(5)M(-1) for 2), and cleaved pBR322 DNA efficiently in the mediation of ascorbic acid (AA), probably via an oxidative damage mechanism induced by OH. The antioxidant activities of the complexes have been evaluated by means of modified nitroblue tetrazolium (NBT) photoreduction and cellular antioxidant activity (CAA) assays using HepG2 cells as a model, and it was found that IC50 values of 1 and 2 for dismutation of O2(-) were 0.172 and 0.247μM, respectively, and the CAA50 values were 10.57 and 10.74μM. In addition, the complexes were subjected to in vitro cytotoxicity against three human carcinoma cell lines (HeLa, A549 and HepG2), which revealed that the complexes exhibited effective cytotoxicity (IC50 values varying from 33.17 to 100μM) and selective inhibition toward HeLa cell lines. These findings indicate that the complexes have the potential to act as effective metallopeptide chemotherapeutic agents.

A new ternary copper(II) complex derived from 2-(2'-pyridyl)benzimidazole and glycylglycine: synthesis, characterization, DNA binding and cleavage, antioxidation and HSA interaction

A new ternary copper(II)-dipeptide complex [Cu(glygly)(HPB)(Cl)]⋅2H2O (glygly=glycylglycine anion, HPB=2-(2'-pyridyl)benzimidazole) has been synthesized and characterized. The DNA interaction of the complex was studied by spectroscopic methods, viscosity, and electrophoresis measurements. The antioxidant activity was also investigated using the pyrogallol autoxidation assay. Besides, the interaction of the complex with human serum albumin (HSA) in vitro was examined by multispectroscopic techniques. The complex partially intercalated to CT-DNA with a high binding constant (Kb=7.28×10(5) M(-1)), and cleaved pBR322 DNA efficiently via an oxidative mechanism in the presence of Vc, with the HO· and O2(-) as the active species, and the SOD as a promoter. Furthermore, the complex shows a considerable SOD-like activity with the IC50 value of 3.8386 μM. The complex exhibits desired binding affinity to HSA, in which hydrogen bond or vander Waals force played a major role. The alterations of HSA secondary structure induced by the complex were confirmed by UV-visible, CD, synchronous fluorescence and 3D fluorescence spectroscopy.

Aquachloridobis[2-(1,3-thia-zol-4-yl-κN)-1H-benzimidazole-κN(3)]nickel(II) nitrate

In the title compound, [NiCl(C₁₀H₇N₃S)₂(H₂O)]NO₃, the Ni^II ion is coordinated by four N atoms from two chelating 2-(1,3-thia­zol-4-yl)-1H-benzimidazole ligands, one Cl atom and one water mol­ecule in a distorted octa­hedral geometry. In the crystal, O—H⋯O, N—H⋯O and N—H⋯Cl hydrogen bonds link the complex cations and nitrate anions into a three-dimensional network. π–π inter­actions between the thia­zole and imidazole rings and between the thia­zole and benzene rings are observed [centroid–centroid distances = 3.592 (3) and 3.735 (3) Å].

Chloridobis[2-(1,3-thia-zol-4-yl-κN)-1H-benzimidazole-κN(3)]cobalt(II) chloride dihydrate

In the title compound, [CoCl(C₁₀H₇N₃S)₂]Cl·2H₂O, the Co^II atom is five-coordinated by four N atoms from two chelating 2-(1,3-thia­zol-4-yl)-1H-benzimidazole ligands and one Cl atom in a distorted trigonal–bipyramidal geometry. In the crystal, N—H⋯O and O—H⋯Cl hydrogen bonds and π–π inter­actions between the thia­zole, imidazole and benzene rings [centroid-to-centroid distances 3.546 (2), 3.683 (2) and 3.714 (2) Å] link the complex cations, chloride anions and uncoordinating water mol­ecules into a three-dimensional network.

Structural and spectroscopic characterization of 2-mesityl-1H-benzo[d]imidazol-3-ium chloride: a combined experimental and theoretical analysis

The title molecular salt, 2-mesityl-1H-benzo[d]imidazol-3-ium chloride (C(16)H(17)N(2)(+)·Cl-), was synthesized unexpectedly from the reaction of N-[(1E)-mesitylmethylene]benzene-1,2-diamine and CoCl(2)·6H(2)O, and characterized by elemental analysis, (1)H NMR and FT-IR spectroscopies, and single-crystal X-ray diffraction technique. In addition, quantum chemical calculations employing density functional theory (DFT) method with the 6-311++G(d,p) basis set were performed to study the molecular, spectroscopic and some electronic structure properties of the title compound, and the results were compared with the experimental findings. The computational result shows that the optimized geometry can well reproduce the crystal structural parameters. The intermolecular proton transfer process between the ionic (C(16)H(17)N(2)(+)·Cl-) and nonionic forms (C(16)H(16)N(2)·HCl) of the title salt is investigated and found to be almost barierless with an energy value of 0.20 kcal mol(-1). The NLO properties of the compound are bigger than those of urea.

Spectral characterization and antimicrobial activity of 2-(5-chloro/nitro-1H-benzimidazol-2-yl)-4-bromo/nitro-phenols and their zinc(II) complexes

2-(5-Chloro/nitro-1H-benzimidazol-2-yl)-4-bromo/nitro-phenols (HL(x); x=1-4) and their complexes with zinc(II)nitrate have been synthesized and characterized. In the tetrahedral mononuclear complexes, the ligands are bidentate, via the imine nitrogen and the phenolate oxygen atoms. The structures of the complexes were confirmed on the basis of elemental analysis, molar conductivity, TGA, FT-IR, NMR, mass and UV-vis spectroscopy. The optimized geometry of the complexes was derived from theoretical calculation in DGauss/DFT level on CACHE program. From theoretical calculations it was found that bromo derivatives of the ligands (HL(1) and HL(3)) have higher stability than the other ligands and similarly, their Zn(II) complexes have higher stability than the other complexes. The antimicrobial activities of the compounds were evaluated using the disk diffusion method against six bacteria and Candida albicans. All of the complexes exhibited selective antibacterial activity on Staphylococcus epidermidis. HL(3) and [Zn(L(1))(2)].H(2)O are more active than Ciprofloxazin and, [Zn(L(2))(2)] has antibacterial activity as potent as Ciprofloxazin against S. epidermidis.

Oxazoles XXII. The Cobalt(II) Coordination Chemistry of 2-(ortho-Anilinyl)-4,4-dimethyl-2-oxazoline: Syntheses, Properties, and Solid-State Structural Characterization

Ethanol solutions of the cobalt(ii) halides react with an excess of 2-(ortho-anilinyl)-4,4-dimethyl-2-oxazoline (1: i.e. 2-(2′-anilinyl)-4,4-dimethyl-4,5-dihydro-1,3-oxazole) to give isolable κ2-N,N′-bonded species of 1 in good to excellent yields. The complexes CoX2(1-κ2-N,N′)·(H2O) n have been isolated for X = Cl (2: n = 1/2), X = Br and I (3 and 4, respectively; n = 0); the solid-state structures (X-ray) are in accordance with those suggested by UV-visible spectroscopy and conductivity measurements (i.e. non-ionic complexes with a pseudo-tetrahedral coordination motif around Co). In contrast, reaction of excess 1 with Co(NCS)2 forms the octahedral (UV-visible, X-ray) bis-isothiocyanato complex Co(NCS-κ1-N′)2(1-κ2-N,N′)2 (5) with cis-oriented NCS groups and trans-disposed oxazolines. Calculations at the PM3(tm) level of theory suggest that this isomer is close in energy to the four other possible (gas-phase) isomers. Treatment of ethanol solutions of hydrated cobaltous nitrate with excess 1 yields a material analyzed as [Co(NO3)(1)(H2O)2](NO3) (6a) and a small amount (less than 1%) of a second complex (6b); the latter has been characterized (X-ray) as the hydrated octahedral complex [Co(NO3-κ1-O)(1-κ2-N,N′)2(OH2)](NO3). In this case, the nitrato and aqua groupings are located cis to one another and trans to the coordinated –NH2 groups. Complex 6a is surmised to have a [Co(NO3-κ2-O,O′)2(1-κ2-N,N′)(OH2)2]NO3 structure. Cobalt compounds 2–5 and 1 have also been screened for their antifungal properties against Aspergillus niger, Aspergillus flavus, Candida albicans, and Saccharomyces cerevisiae but were found to be inactive in this regard.

Preparation, characterization and antibacterial effect of 2-methoxy-6-(5-H/Me/Cl/No2-1H-benzimidazol-2-yl)phenols and some transition metal complexes

2-Methoxy-6-(5-H/methyl/chloro/nitro-1H-benzimidazol-2-yl)phenols (HLx; x = 1-4, respectively) ligands and HL1 complexes with Fe(NO3)3, Cu(NO3)2, AgNO3 and Zn(NO3)2 were synthesized and characterized. The structures of the compounds were confirmed based on elemental analysis, molar conductivity, magnetic moment, FT-IR, 1H- and 13C-NMR. The antibacterial activity and minimum inhibitory concentration (MIC) of the free ligands, their hydrochloride salts and the complexes were evaluated using the disk diffusion method in dimethyl sulfoxide (DMSO) and the dilution method, respectively, against 9 bacteria. HL1 and HL3, as well as the Cu(II) and Zn(II) complexes, showed antibacterial activity against Gram-positive bacteria.

Raman, FT-IR, NMR spectroscopic data and antimicrobial activity of bis[μ2-(benzimidazol-2-yl)-2-ethanethiolato-N,S,S-chloro-palladium(II)] dimer, [(μ2-CH2CH2NHNCC6H4)PdCl]2·C2H5OH complex

The 1,6-bis(benzimidazol-2-yl)-3,4-dithiahexane (1) ligand and its palladium(II) chloride complex [(micro(2)-SCH(2)CH(2)NHNCC(6)H(4))PdCl](2)xC(2)H(5)OH (2) have been synthesised and characterised by spectroscopical methods. The crystal structure of the triclinic title compound (P-1 (no. 2), a=879.6(1) pm, b=984.4(1) pm, c=1471.8(2) pm; alpha=94.330(6) degrees , beta=98.546(6) degrees , gamma=99.258(7) degrees , Z=2) was solved from X-ray single crystal diffraction data. In the binuclear complex, each palladium atom is coordinated in a slightly distorted square-planar arrangement by one nitrogen, two bridging sulphurs and one terminal chlorine atom. Molar conductivity, FT-Raman, FT-IR (mid-i.r., far-i.r.), (1)H and (13)C NMR spectra of the complex (2) have been recorded and show a good accordance with the square-planar geometry. The antimicrobial and antifungal activities of palladium(II) chloride, free ligand, its hydrochloride salt and the complex were evaluated using the disk diffusion method in dimethyl sulfoxide (DMSO) as well as the minimal inhibitory concentration (MIC) the dilution method, against 10 bacteria and five yeast cultures. The results for the antibacterial from the disk diffusion method were assessed in side-by-side comparison with those for penicillin-g, ampicillin, cefotaxime, vancomycin, ofloxacin and tetracycline. Antifungal activities were referenced with nystatin, ketaconazole, and clotrimazole, commercial antifungal agents. The data from the dilution procedure were compared with gentamycin as antibacterial and nystatin as antifungal agent, respectively. In most cases, the compounds tested showed broad-spectrum (Gram positive and Gram negative) activities that were comparatively more active, or as potent as referenced pharmaceutical agents. The palladium complex has the potential to generate new kind of metabolites by displaying high affinities for most of the receptors compared with palladium chloride, free ligand and its hydrochloride salt.

Photodynamic Action and Antimicrobial Activity of Some Excited Metabolites ofDalbergia Sissoidesand Their Ability to Cleave DNA

The photodynamic properties of two quinones, 4-methoxydalbergione (DS1) and sissoidenone (DS2), and a coumarin, dalbergin {6-hydroxy-7-methoxy-4-phenylcoumarin, (DS3)}, have been studied. Photogeneration of singlet oxygen (1O2) was monitored by both optical and EPR methods. Based on RNO bleaching, relative to Rose Bengal (RB), the singlet oxygen generating efficiencies of DS1, DS2, and DS3 were determined as 0.10, 0.051 and 0.041, respectively. Using the SOD inhibitable cytochrome c reduction assay, the photogeneration of superoxide anion (O2-•) was monitored. The formation of O2-•was enhanced in the presence of electron donors such as EDTA, DETAPAC and NADH. Photolysis of DS1 and DS3 in DMSO in the presence of 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) generated a twelve line EPR spectrum characteristic of an O2-•adduct. In the photosensitization of the DS series, both Type I and Type II paths were involved. The quantum mechanically calculated lowest unoccupied molecular orbital (LUMO) energies of DS1 and DS2 were correlated with the experimental redox potential. Photoinduced DNA scission by DS1, DS2, and DS3 confirms the generation of O2-•from these metabolites.

Metal-Mediated Inhibition of Escherichia coli Methionine Aminopeptidase: Structure−Activity Relationships and Development of a Novel Scoring Function for Metal−Ligand Interactions

We report the discovery of thiabendazole as a potent inhibitor (K(i) = 0.4 microM) of Escherichia coli methionine aminopeptidase (ecMetAP) and the synthesis and pharmacological evaluation of thiabendazole congeners with activity in the upper nanomolar range. Elucidation of the X-ray structure of ecMetAP in complex with thiabendazole and an unrelated inhibitor that was independently described by another group showed that that both compounds bind to an additional Co(II) ion at the entrance of the active site. This unexpected finding explains the inactivity of the compounds under in vivo conditions. It also allows us to discuss the structure-activity relationships of this series of compounds in a meaningful way, based upon docking runs with an auxiliary metal ion. We describe a new scoring function for the evaluation of metal-mediated inhibitor binding that, unlike the previously used scoring function implemented in the docking program, allows us to distinguish between active and inactive compounds. Finally, conclusions for the structure-based design of in vivo-active inhibitors of ecMetAP are drawn.

Structural characterization and antimicrobial activity of 1,3-bis(2-benzimidazyl)-2-thiapropane ligand and its Pd(II) and Zn(II) halide complexes

1,3-Bis(2-benzimidazyl)-2-thiapropane(L) forms 5-coordinate square pyramidal and 4-coordinate tetrahedral, monometallic complexes with PdCl(2) and ZnX(2) (X=Cl, Br, I), respectively. In the palladium complex, the ligand acts as a chelating tridentate, through two of the nitrogen atoms in the imidazole ring and the sulfur atom of the bridging group together with two chloride ions forming a rare five coordinate complex. In the zinc halide complexes, the ligand acts as chelating bidentate, via two of the nitrogen atoms combined with two halide ions giving common tetrahedral complexes. The ligand and its complexes are characterized by analytical data and spectroscopic methods such as FT-Raman, FT-IR (mid-IR, far-IR), (1)H and (13)C NMR. Their antimicrobial activities are evaluated by the minimal inhibitory concentration (MIC) against 10 bacteria, each with multiple, fresh clinical isolates (10-15), and the results are compared with those of ampicillin, ciprofloxacin, cefazolin, ofloxacin, and piperacillin antibacterial agents. The compound's antifungal activities are reported on Candida albicans, Candida utilis, and Cryptococcus neoformans yeasts, each with multiple isolates (10), and the results are referenced with amphotericin-B, fluconazole and flucytosine antifungal agents. In most cases, the compounds show broad-spectrum (Gram(+) and Gram(-)) activities that are either, more active, or equipotent to, the antibiotic and antifungal agents in the comparison tests.