Spectroscopic, DFT, biological, DNA-binding, and antioxidant studies of some metal chelates with a novel thiazole-derived Schiff base

Spectroscopic, docking, antiproliferative, and anticancer activity of novel metal derivatives of phenylacetohydrazide Schiff base on different human cancer cell lines

In the last two decades, many Schiff bases have been investigated due to the importance of their metal complexes in the medical field and drug industry. The Schiff base metal complexes have several applications as anticancer agents because they have a high binding ability to nucleic acids (DNA and RNA). The Schiff base H2L, derived from the condensation of 2-phenylacetohydrazide and 2-hydroxynaphthaldehyde, was reacted with Fe2+, Zn2+, Cd2+, and Pt2+ to form the unique metal complexes [Fe(HL)2], [Zn2(HL)2](CH3COO)2, [Cd2(HL)2](CH3COO)2, and [Pt(H2L)Cl2]. Various analytical and spectroscopic techniques were used to characterize the newly reported compounds. The elemental and spectroscopic analysis revealed that the platinum complex was a square planar with 2.5 water molecules in the crystal lattice, whereas the iron complex had an octahedral geometry. The thermogravimetric analysis demonstrated the stability of the complexes and validated the dimerization of zinc and cadmium complexes. DFT calculations were investigated to obtain the optimized structure of the ligand and its complexes. Biological screening and molecular docking studies of the ligand and complexes were reported to explore their potential application as therapeutic drugs. Among the tested complexes, [Cd2(HL)2](CH3COO)2 complex showed the best cytotoxic effect, especially on the human colorectal cancer cell line (HCT116, IC50 = 0.329 µg/ml) as compared to normal human skin fibroblast (HSF, IC50 = 5.240 µg/ml) and selectivity index (SI) = 15.93. It represents a promising anticancer drug compared to Cisplatin (IC50 = 2.25µg/ml, SI = 4.92). The biological studies and molecular docking were correlated to each other.

Synthesis, spectroscopic, DFT calculations, biological activity, SAR, and molecular docking studies of novel bioactive pyridine derivatives

Enaminonitrile pyridine derivative was used as a precursor for preparation of fourteen heterocyclic compounds using both conventional thermal and microwave techniques. Diverse organic reagents, such as chloroacetyl chloride, acetic anhydride, chloroacetic acid, carbon disulfide, p-toluene sulfonyl chloride, maleic anhydride, phthalic anhydride, were used. The chemical formulae and structures of isolated derivatives were obtained using different analytical and spectroscopic techniques such as IR, 1H-, 13C-NMR as well as mass spectrometry. The spectroscopic analyses revealed diverse structure arrangements for the products. Molecular structure optimization of certain compounds were performed by the density functional theory (DFT/B3LYP) method and the basis set 6-31 G with double zeta plus polarization (d,p). The antimicrobial inhibition and the antioxidant activity of the reported compounds were screened. Compounds 5, 6, 11 and 13 exhibited the highest antibacterial inhibition, while compound 8 gave the highest scavenging activity (IC50 43.39 µg/ml) against the DPPH radical. Structure-activity relationship of the reported compounds were correlated with the data of antibacterial and the antioxidant activity. The global reactivity descriptors were also correlated with the biological properties of compounds. The molecular docking studies of reported compounds were investigated, and the analysis showed that the docked compounds have highly negative values for the functional binding scores. The binding interaction was found to be correlated with the substituent fragments of the compounds.

Design, synthesis, biomedical investigation, DFT calculation and molecular docking of novel Ru(II)-mixed ligand complexes

A novel series of bioactive water-soluble mononuclear Ru(II)-mixed ligand complexes of 2,2'-bipyridyl and V-shaped Schiff base ligands were synthesized and structurally characterized. Biomedical activities of Ru(II) complexes have been tested in view of antioxidant activities, interaction with calf thymus DNA (CT-DNA), and anticancer performance. The optimized structure of these complexes has been further supported by density functional theory (DFT) calculations. Further, validation of the interaction studies of some complexes was accomplished by carrying out molecular docking studies with DNA using molecular operating environment (MOE) software are reported.Communicated by Ramaswamy H. Sarma.

Metal incorporated aminothiazole-derived compounds: synthesis, density function theory analysis, in vitro antibacterial and antioxidant evaluation

The present study advocates the combined experimental and computational study of metal-based aminothiazole-derived Schiff base ligands. The structure and electronic properties of ligands have been experimentally studied by spectroscopic methods (UV-Vis, FT-IR, ¹H-NMR and ¹³C-NMR), mass spectrometry, elemental analysis and theoretically by density function theory (DFT). Computational calculations employing the B3LYP/6-31 + G(d,p) functional of DFT were executed to explore the optimized geometrical structures of ligands along with geometric parameters, molecular electrostatic potential (MEP) surfaces and frontier molecular orbital (FMO) energies. Global reactivity parameters estimated from FMO energy gaps signified the bioactive nature of ligands. The synthesized ligands were used for chelation with 3d-transition metals [VO(IV), Cr(III), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II)] in 1 : 2 (metal : ligand) molar ratio. The spectral and magnetic results confirmed the formation of octahedral geometry around all the divalent and trivalent metal centres, whereas the tetravalent vanadyl centres were confirmed to have square-pyramidal geometry. All the as-synthesized compounds were investigated for in vitro antibacterial potential against two Gram-negative (Salmonella typhimurium and Escherichia coli) and two Gram-positive (Bacillus subtilis and Staphylococcus aureus) bacteria. Antibacterial assay results displayed pronounced activity, and their activity is comparable to that of a standard drug (streptomycin). The antioxidant potential of these compounds was assessed by employing diphenyl picryl hydrazide radical scavenging activity. The results displayed that all the metal chelates have exhibited more bioactivity in contrast with free ligands. The chelation was the main reason for their enhanced bioactivity. These results indicated that the thiazole metal-based compounds could be exploited as antioxidant and antimicrobial candidates.