New Cu(II), Co(II), Ni(II) complexes with aroyl-hydrazone based ligand. Synthesis, spectroscopic characterization and in vitro antibacterial evaluation

In vitro anti-bacterial and time kill evaluation of binuclear tricyclohexylphosphanesilver(I) dithiocarbamates, {Cy3PAg(S2CNRR')}2

Four binuclear phosphanesilver(I) dithiocarbamates, {cyclohexyl₃PAg(S₂CNRR')}₂ for R = R' = Et (1), CH₂CH₂ (2), CH₂CH₂OH (3) and R = Me, R' = CH₂CH₂OH (4) have been synthesised and characterised by spectroscopy and crystallography, and feature tri-connective, μ₂-bridging dithiocarbamate ligands and distorted tetrahedral geometries based on PS₃ donor sets. The compounds were evaluated for anti-bacterial activity against a total of 12 clinically important pathogens. Based on minimum inhibitory concentration (MIC) and cell viability tests (human embryonic kidney cells, HEK 293), 1-4 are specifically active against Gram-positive bacteria while demonstrating low toxicity; 3 and 4 are active against methicillin resistant S. aureus (MRSA). Across the series, 4 was most effective and was more active than the standard anti-biotic chloramphenicol. Time kill assays reveal 1-4 to exhibit both time- and concentration-dependent pharmacokinetics against susceptible bacteria. Compound 4 demonstrates rapid (within 2 h) bactericidal activity at 1 and 2 × MIC to reach a maximum decrease of 5.2 log₁₀ CFU/mL against S. aureus (MRSA).

Cytotoxic homoleptic Ti(iv) compounds of ONO-type ligands: synthesis, structures and anti-cancer activity

Reacting variously substituted dianionic tridentate ONO-type acylhydrazone ligands with titanium(iv) tetra(isopropoxide) gave a new class of eight homoleptic titanium(iv) compounds showing exceptional stability and promising cytotoxicity.

A selective detection approach for copper(ii) ions using a hydrazone-based colorimetric sensor: spectroscopic and DFT study

The development of an efficient and miniaturized analytical approach to determine trace levels of toxic ions in aqueous fluids presents a current research challenge. Hydrazone-based chemosensors are considered potential candidates due to their high sensitivity and selectivity towards heavy metal ions. Computational techniques can be properly implemented to elucidate possible modes of ligand-metal interaction and provide an in-depth understanding of the chemistry involved. The present study reports the use of 3-hydroxy-5-nitrobenzaldehyde-4-hydroxybenzoylhydrazone (3-HNHBH) ligand for highly sensitive, quick and re-usable colorimetric sensing of copper(ii) ions in aqueous media. DFT calculations suggest that the complexation of 3-HNHBH with copper(ii) ions adopts a seesaw coordination geometry and results in the largest HOMO-LUMO gap and most effective coulombic interaction compared to Zn and Ni counterparts. It demonstrated a high selectivity towards copper ions with a detection limit of 0.34 μg L-1. The ligand was readily regenerated using a 0.5 M HCl solution, indicating its feasibility to be used as a re-usable sensor for the convenient detection of copper ions in aqueous media. The influence of metal interference, pH and solvents on the selectivity and regeneration of the ligand was also investigated.

Synthesis and evaluation of the antibiotic and adjuvant antibiotic potential of organotin(IV) derivatives

A series of organotin(IV) derivatives was investigated in vitro for their antibiotic and adjuvant antibiotic properties (efflux pump inhibitors) against Staphylococcus aureus strains that overexpress efflux pump proteins for norfloxacin (SA-1199B), erythromycin (RN-4220) and tetracycline (IS-58). Most organotin(IV) compounds showed significant antibacterial activity with small Minimum Inhibitory Concentration (MIC) values, some of which were close to 1.0μg/mL (3.1μM), but this feature was also associated with substantial cytotoxicity. Nevertheless, the cytotoxicity of these organotin(IV) compounds can be overcome when they are used as antibiotic adjuvants. Their remarkable adjuvant antibiotic properties allow potentiation of the action of tetracycline (against IS-58 strain) by up to 128-fold. This likely indicates that they can act as putative inhibitors of bacterial efflux pumps. These results reinforce organotin(IV) complexes as promising antibacterial agents, and many of these complexes, if associated with antibiotics, can act as potential adjuvant antibiotic candidates.

Design, synthesis, conformational and molecular docking study of some novel acyl hydrazone based molecular hybrids as antimalarial and antimicrobial agents

BACKGROUND

Acyl hydrazones are an important class of heterocyclic compounds promising pharmacological characteristics. Malaria is a life-threatening mosquito-borne blood disease caused by a plasmodium parasite. In some places, malaria can be treated and controlled with early diagnosis. However, some countries lack the resources to do this effectively.

RESULTS

The present work involves the design and synthesis of some novel acyl hydrazone based molecular hybrids of 1,4-dihydropyridine and pyrazole (5a-g). These molecular hybrids were synthesised by condensation of 1,4-dihydropyridin-4-yl-phenoxyacetohydrazides with differently substituted pyrazole carbaldehyde. The final compound (5) showed two conformations (the major, E, s-cis and the minor, E, s-trans) as revealed by NMR spectral data and further supported by the energy calculations (MOPAC2016 using PM7 method). All the synthesised compounds were screened for their in vitro antimalarial activities against chloroquine-sensitive malaria parasite Plasmodium falciparum (3D7) and antimicrobial activity against Gram positive bacteria i.e. Bacillus cereus, Gram negative bacteria i.e. Escherichia coli and antifungal activity against one fungus i.e. Aspergillus niger [corrected]. All these compounds were found more potent than chloroquine and clotrimazole, the standard drugs.

CONCLUSIONS

In vitro antiplasmodial IC₅₀ value of the most potent compound 5d was found to be 4.40 nM which is even less than all the three reference drugs chloroquine (18.7 nM), pyrimethamine (11 nM) and artimisinin (6 nM). In silico binding study of compound 5d with plasmodial cysteine protease falcipain-2 indicated the inhibition of falcipain-2 as the probable reason for the antimalarial potency of compound 5d. All the compounds had shown good to excellent antimicrobial and antifungal activities.

Crystal structure of (E)-1-[1-(3-chloro-4-fluoro-phenyl)ethylidene]-2-(2,4-dinitrophenyl)hydrazine, C28H20Cl2F2N8O8

C28H20Cl2F2N8O8, triclinic, P1̅ (no. 2), a = 9.045(3) Å, b = 10.907(4) Å, c = 15.351(5) Å, α = 93.416(7)°, β = 95.771(7)°, γ = 95.915(6)°, V = 1495.0(9) Å3, Z = 4, R gt(F) = 0.0655, wR ref(F 2) = 0.1940, T = 293 K.

Ni(ii) and Co(ii) complexes of an asymmetrical aroylhydrazone: synthesis, molecular structures, DNA binding, protein interaction, radical scavenging and cytotoxic activity

The DNA/BSA binding, antioxidant and cytotoxic activity of Ni(ii) and Co(ii) complexes bearing aroylhydrazone were investigated to induce apoptosis in cancer cells.

Substituted tetrazoles as multipurpose screening compounds

Tetrazoles are small functional heterocycles that are suited to serve simultaneously as aromatic platform for diversity and as functional interaction motif. Furthermore, the tetrazole ring and its deprotonated tetrazolate counterpart are metal ion complexing ligands that possess a rich variety of binding and bridging modes. We recently demonstrated that fragments containing the tetrazole moiety and a metal chelating hydrazide group are well suited to discover selective screening hits with high ligand efficiency for a given protein target. Here, we report the synthesis and characterization of new polydentate tetrazole-containing screening compounds and their synthetic precursors as well as their deposition in a multipurpose screening library in the frame of the EU-OPENSCREEN network. The pure and well-characterized screening compounds could be useful to aid drug discovery programs for multiple or hitherto undruggable targets by enclosure of under-represented tetrazole derivatives.

Zinc asparaginate supplementation induces redistribution of toxic trace elements in rat tissues and organs

The primary objective of the current study was the investigation of the influence of zinc asparaginate supplementation for 7 and 14 days on toxic metal and metalloid content in rat organs and tissues. Rats obtained zinc asparaginate in doses of 5 and 15 mg/kg/day for 7 and 14 days. At the end of the experiment rat tissues and organs (liver, kidney, heart, m. gastrocnemius, serum, and hair) were collected for subsequent analysis. Estimation of Zn, Al, As, Li, Ni, Sn, Sr content in the harvested organs was performed using inductively coupled plasma mass spectrometry at NexION 300D. The obtained data showed that intragastric administration of zinc significantly increased liver, kidney and serum zinc concentrations. Seven-day zinc treatment significantly affected the toxic trace element content in the animals’ organs. Zinc supplementation significantly decreased particularly liver aluminium, nickel, and tin content, whereas lead tended to increase. Zinc-induced changes in kidney metal content were characterized by elevated lithium and decreased nickel concentration. Zinc-induced alteration of myocardical toxic element content was multidirectional. Muscle aluminium and lead concentration were reduced in response to zinc supplementation. At the same time, serum and hair toxic element concentrations remained relatively stable after 7-day zinc treatment. Zinc asparaginate treatment of 14 days significantly depressed liver and elevated kidney lithium content, whereas a significant zinc-associated decrease was detected in kidney strontium content. Zinc supplementation for 14 days resulted also in multidirectional changes in the content of heart toxic elements. At the same time, significant zinc-associated decrease in muscle lithium and nickel levels was observed. Fourteen-day zinc treatment resulted in significantly increased serum arsenic and tin concentrations, whereas hair trace element content remained relatively stable. Generally, the obtained data indicate a significant redistribution of toxic metals in the animal organism under zinc supplementation.

Synthesis, spectral characterization, DNA interaction, radical scavenging and cytotoxicity studies of ruthenium(II) hydrazone complexes

Three new ruthenium(II) complexes with hydrazone ligands, furan-2-carboxylic acid (2,4-dihydroxy-benzylidene)-hydrazide (HL(1)), furan-2-carboxylic acid [4-(ethyl-propyl-amino)-2-hydroxy-benzylidene]-hydrazide (HL(2)) and furan-2-carboxylic acid (3-ethoxy-2-hydroxy-benzylidene)-hydrazide (HL(3)) were synthesized and characterized by various spectro-analytical techniques. The hydrazone ligands act as a tridendate ligand with ONO as the donor sites and are preferably found in the enol form in all the complexes. The molecular structure of the ligands was determined by single crystal X-ray diffraction technique. The interaction of the ligands and the complexes with CT-DNA were evaluated by an absorption titration method which revealed that the compounds interact with CT-DNA through intercalation. Gel electrophoresis assay demonstrated the ability of the complexes to cleave the calf thymus DNA hydrolytically. Antioxidant studies showed that the ruthenium(II) complexes have a strong radical-scavenging properties. Further, the cytotoxic effect of the compounds examined on cancerous cell lines showed that the complexes exhibited substantial anticancer activity.

Bivalent transition metal complexes of ONO donor hydrazone ligand: Synthesis, structural characterization and antimicrobial activity

Mononuclear transition metal complexes of Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) with a new hydrazone ligand derived from pyrazine-2-carbohydrazide and 2-hydroxyacetophenone have been synthesized. The isolated complexes were characterized by elemental analysis, spectral and analytical methods including elemental analyses, IR, diffuse reflectance, (1)H-NMR, mass spectra, molar conductance, magnetic moment, ESR, XRD, TG and SEM analysis. From the elemental analyses data, the stoichiometry of the complexes was found to be 1:1 (metal:ligand) having the general formulae [M(HL)(Cl)(H2O)2], [M=Mn(II), Co(II), Ni(II) and Cu(II)] and [M(L)(H2O)], [M=Zn(II) and Cd(II)]. The molar conductance values indicate the nonelectrolytic nature of metal complexes. The IR spectral data suggest that the ligand behaves as tridentate moiety with ONO donor atoms sequence towards central metal ion. The Mn(II), Co(II), Ni(II) and Cu(II) complexes have been assigned a monomeric octahedral geometry whereas tetrahedral to Zn(II) and Cd(II) complexes. The antibacterial and antifungal activities of the ligand and its metal complexes were studied against bacterial species Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus subtilis, Enterococcus faecalis and Streptococcus pyogenes and fungi Candida albicans, Aspergillus niger and Aspergillus clavatus. The activity data show that the metal complexes have a promising biological activity comparable with the parent ligand against all bacterial and fungal species.

Oxidovanadium(v) complexes of aroylhydrazones incorporating heterocycles: synthesis, characterization and study of DNA binding, photo-induced DNA cleavage and cytotoxic activities

The interaction of four neutral oxidovanadium(v) complexes with DNA and their cytotoxic activities have been reported.

Facile solid state ball milling as a green strategy to prepare 2-(2,4-dichlorophenoxy)-N'-(2-hydroxybenzylidene)acetohydrazide complexes

2-(2,4-Dichlorophenoxy)-N'-(2-hydroxybenzylidene)acetohydrazide (H2L) complexes were prepared by ball milling involving the reaction of ligand with Ni(II), Co(II), Cu(II) and VO(II) salts (mechanochemical syntheses). The compounds were elucidated by elemental analysis, spectroscopy (1H NMR, IR, UV-visible, MS spectra), and physical measurements (magnetic susceptibility and molar conductance). IR spectra suggested that the H2L behaved as a monodentate and/or bidentate ligand coordinating via azomethine nitrogen and/or deprotonated enolized carbonyl oxygen. The electronic spectra of the complexes and their magnetic moments provided information about geometries. The antimicrobial activities of the ligand and its complexes were studied against gram positive bacteria; Staphylococcus aureus, gram-negative bacteria; Escherichia coli and pathogenic fungi; Candida albicans by using minimum inhibition concentrations method (MIC). Also, the antioxidant (ABTS-derived free radical method) and cytotoxic (in vitro Ehrlich Ascites) activities of the isolated compounds were evaluated.

Experimental and computational study on 2,2'-[(1E,2E)-hydrazine-1,2-diylidenedi(1E)eth-1-yl-1-ylidene]diphenol and its Ni(II), Pt(II), Pd(II) complexes

2,2'-[(1E,2E)-hydrazine-1,2-diylidenedi(1E)eth-1-yl-1-ylidene]diphenol and its dimeric, binuclear Ni(II), Pd(II) and Pt(II) metal complexes were synthesized. Hydrazine derivative and its complexes were characterized by elemental analyses, LC-MS, IR, electronic spectra, (1)H and (13)C NMR spectra, conductivity and magnetic measurements. 1H and 13C shielding tensors for crystal structure were calculated with GIAO/DFT/B3LYP/6-311++G(d,p) methods in CDCl3. The vibrational band assignments were performed at B3LYP/6-311++G(d,p) theory level combined with scaled quantum mechanics force field (SQMFF) methodology. The antibacterial activities of synthesized compounds were studied against some Gram-positive and Gram-negative bacteria by using the microdilution and disk diffusion method. As the antibacterial activity results evidently show, the compound possessed a broad spectrum of activity against the tested bacteria.