Evaluation of in Vitro Antimicrobial and in Vivo Cytotoxic Properties of Some Novel Titanium-Based Coordination Complexes

Understanding the Artemia Salina (Brine Shrimp) Test: Pharmacological Significance and Global Impact

BACKGROUND

The microplate benchtop brine shrimp test (BST) has been widely used for screening and bio-guided isolation of many active compounds, including natural products. Although the interpretation given to the results appears dissimilar, our findings suggest a correlation between positive results with a specific mechanism of action.

OBJECTIVE

This study aimed to evaluate drugs belonging to fifteen pharmacological categories having diverse mechanisms of action and carry out a bibliometric analysis of over 700 citations related to microwell BST.

METHODS

Test compounds were evaluated in a serial dilution on the microwell BST using healthy nauplii of Artemia salina and after 24 hrs of exposition, the number of alive and dead nauplii was determined, and the LC50 was estimated. A metric study regarding the citations of the BST miniaturized method, sorted by type of documents cited, contributing country, and interpretation of results was conducted on 706 selected citations found in Google Scholar.

RESULTS

Out of 206 drugs tested belonging to fifteen pharmacological categories, twenty-six showed LC50 values <100 μM, most of them belonging to the category of antineoplastic drugs; compounds with different therapeutical uses were found to be cytotoxic as well. A bibliometric analysis showed 706 documents citing the miniaturized BST; 78% of them belonged to academic laboratories from developing countries located on all continents, 63% interpreted their results as cytotoxic activity and 35% indicated general toxicity assessment.

CONCLUSION

BST is a simple, affordable, benchtop assay, capable of detecting cytotoxic drugs with specific mechanisms of action, such as protein synthesis inhibition, antimitotic, DNA binding, topoisomerase I inhibitors, and caspases cascade interfering drugs. The microwell BST is a technique that is used worldwide for the bio-guided isolation of cytotoxic compounds from different sources.

Synthesis, characterization, redox behavior, DNA and protein binding and antibacterial activity studies of ruthenium(II) complexes of bidentate schiff bases

Two new ruthenium(II) complexes of Schiff base ligands (L) derived from cinnamaldehyde and ethylenediamine formulated as [Ru(L)(bpy)₂](ClO₄)₂, where L¹ = N,N'-bis(4-nitrocinnamald-ehyde)ethylenediamine and L² = N,N'-bis(2-nitrocinnamaldehyde)-ethylenediamine for complex 1 and 2, respectively, were isolated in pure form. The complexes were characterized by physicochemical and spectroscopic methods. The electrochemical behavior of the complexes showed the Ru(III)/Ru(II) couple at different potentials with quasi-reversible voltammograms. The interaction of the complexes with calf thymus DNA (CT-DNA) using absorption, emission spectral studies and electrochemical techniques have been used to determine the binding constant, K_b and the linear Stern-Volmer quenching constant, K_SV. The results indicate that the ruthenium(II) complexes interact with CT-DNA strongly in a groove binding mode. The interactions of bovine serum albumin (BSA) with the complexes were also investigated with the help of absorption and fluorescence spectroscopy tools. Absorption spectroscopy proved the formation of a ground state BSA-[Ru(L)(bpy)₂](ClO₄)₂ complex. The antibacterial study showed that the Ru(II) complexes (1 and 2) have better activity than the standard antibiotics but weak activity than the ligands.

Synthesis and Characterisation of Copper(II) Complexes with Tridentate NNO Functionalized Ligand: Density Function Theory Study, DNA Binding Mechanism, Optical Properties, and Biological Application

The photo physical properties of two mononuclear pentacoordinated copper(II) complexes formulated as [Cu(L)(Cl)(H2O)] (1) and [Cu(L)(Br)(H2O)] (2) HL = (1-[(3-methyl-pyridine-2-ylimino)-methyl]-naphthalen-2-ol) were synthesized and characterized by elemental, physicochemical, and spectroscopic methods. The density function theory calculations are used to investigate the electronic structures and the electronic properties of ligand and complex. The interactions of copper(II) complexes towards calf thymus DNA were examined with the help of absorption, viscosity, and fluorescence spectroscopic techniques at pH 7.40. All spectroscopy's result indicates that complexes show good binding activity to calf thymus DNA through groove binding. The optical absorption and fluorescence emission properties of microwires were characterized by fluorescence microscope. From a spectroscopic viewpoint, all compounds strongly emit green light in the solid state. The microscopy investigation suggested that microwires exhibited optical waveguide behaviour which are applicable as fluorescent nanomaterials and can be used as building blocks for miniaturized photonic devices. Antibacterial study reveals that complexes are better antimicrobial agents than free Schiff base due to bacterial cell penetration by chelation. Moreover, the antioxidant study of the ligand and complexes is evaluated by using 1,1-diphenyl-2-picrylhydrazyl (DPPH) free-radical assays, which demonstrate that the complexes are of higher antioxidant activity than free ligand.

Synthesis, spectral characterization and biological activities of Mn(II) and Co(II) complexes with benzyloxybenzaldehyde-4-phenyl-3-thiosemicarbazone

Mn(II) and Co(II) complexes of benzyloxybenzaldehyde-4-phenyl-3-thiosemicarbazone have been synthesized and characterized by the investigations of electronic and EPR spectra and X-ray diffraction. Based on the spectral studies, an octahedral geometry is assigned for the Mn(II) and Co(II) complexes. X-ray powder diffraction studies reveal that Mn(II) and Co(II) complexes have triclinic crystal lattices. The unit cell parameters of the Mn(II) complex are a=11.0469 Å, b=6.2096 Å, c=7.4145 Å, α=90.646°, β=95.127°, γ=104.776°, V=489.7 Å(3) and those of Co(II) complex are a=9.3236 Å, b=10.2410 Å, c=7.8326 Å, α=90.694°, β=99.694°, γ=100.476°, V=724.2 Å(3). When the free ligand and its metal complexes are subjected to antibacterial activity, the metal complexes are proved to be more active than the ligand. However with regard to in vitro antioxidant activity, the ligand exhibits greater antioxidant activity than its metal(II) complexes.

Copper(II) and nickel(II) complexes of benzyloxybenzaldehyde-4-phenyl-3-thiosemicarbazone: Synthesis, characterization and biological activity

Benzyloxybenzaldehyde-4-phenyl-3-thiosemicarbazone ligand (L) has been synthesized from benzyloxybenzaldehyde and 4-phenyl-3-thiosemicarbazide. Complexes of this ligand with chlorides of Cu(II) and Ni(II) have been prepared. The structure of the ligand (L) is proposed based on elemental analysis, IR and (1)H NMR spectra. Its complexes with Cu(II) and Ni(II) ions are characterized from the studies of electronic as well as EPR spectra. On the basis of electronic and EPR studies, rhombically distorted octahedral structure has been proposed for Cu(II) complex while the Ni(II) complex has been found to acquire an octahedral structure. The ligand and their metal complexes have been tested in vitro for their biological effects. Their antibacterial activities against Gram-negative bacteria (Escherichia coli and Klebsiella pneumoniae) and Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis) have been investigated. The prepared metal complexes exhibit higher antibacterial activities than the parent ligand. The in vitro antioxidant activity of free ligand and its metal(II) complexes have also been investigated and the results however reveal that the ligand exhibits greater antioxidant activity than its complexes.

Novel thiocyanato complexes with potent cytotoxic and antimicrobial properties

The aim of the present study was to assess the cytotoxic and antimicrobial properties of seven new thiocyanato complexes: Ni(C9H11N2O)(SCN), Cu(C9H11N2O)(SCN), Pd(C9H11N2O)(SCN), Pt(C9H11N2O) (SCN), K[Ti(C9H11N2O)(SCN)3], Au(C9H11N2O)(SCN), and K[V(O)(C9H11N2O)(SCN)] (T1-T7, respectively). All the complexes showed toxicity against brine shrimp nauplii (Artemia salina L.). The titanium-based complex, T5, exhibited potent toxicity, with a lethal concentration 50% (the concentration of test compound that kills 50% of A. salina) value of 1.59 μg mL−1. These new complexes also exhibited promising antibacterial and antifungal properties. A macrodilution technique was used to estimate the minimum inhibitory concentrations of the seven bioactive complexes. Minimum inhibitory concentrations were found to be 8–64 μg mL−1 against the tested bacterial species.

Synthesis, spectroscopic, and antimicrobial studies on bivalent zinc and mercury complexes of 2-formylpyridine thiosemicarbazone

A series of metal complexes of Zn(II) and Hg(II) having the general composition [M(L)₂]X₂ [where L = 2-formylpyridine thiosemicarbazone; M = Zn(II) and Hg(II); X = Cl⁻, NO₃⁻ and 1/2SO₄²⁻] have been prepared and characterized by elemental chemical analysis, molar conductance, and spectral (IR and mass) studies. The IR spectral data suggests the involvement of sulphur and azomethane nitrogen in coordination to the central metal ion. On the basis of spectral studies, a tetrahedral geometry has been assigned for Zn(II) and Hg(II) complexes. The free ligand and its metal complexes have been tested in vitro against a number of microorganisms in order to assess their antimicrobial properties.

Biological Screening of a Novel Nickel (II) Tyrosine Complex

A newly synthesized Nickel (II) tyrosine complex was screened as potential antimicrobial agent against a number of medically important bacteria (Bacillus subtilis, Streptococcus β-haemolytica, Escherichia coli, Shigella dysenterae) and fungi (Aspergillus fumigatus, Candida albicans, Aspergillus niger, Aspergillus flavus, Penicillium sp.) strains. were used for antifungal activity. The antimicrobial activity was evaluated using the Agar Disc method. Moreover, the minimum inhibitory concentration of the complexes was determined against the same pathogenic bacteria and the values were found between 4~64 µg ml (-1). Brine shrimp bioassay was carried out for cytotoxicity measurements of the complexes. The LC50 values were calculated after probit transformation of the resulting mortality data and found to be 6 µg ml (-1).