Synthesis, characterization and nucleic acid binding studies of mononuclear copper(II) complexes derived from azo containing O, O donor ligands

Non-covalent binding interaction of bioactive coumarin esculetin with calf thymus DNA and yeast transfer RNA: A detailed investigation to decipher the binding affinities, binding location, interacting forces and structural alterations at a molecular level

Esculetin is a well-known coumarin derivative found abundantly in nature possessing an extensive array of pharmacological and therapeutic properties. Consequently, to comprehend its molecular recognition mechanism, our objective is to conduct a complete investigation of its interactions with the nucleic acid, specifically ct-DNA, and t-RNA, using spectroscopic and computational techniques. The intrinsic fluorescence of esculetin is quenched when it interacts with ct-DNA and t-RNA, and this occurs through a static quenching mechanism. The thermodynamic parameters demonstrated that the interaction is influenced by hydrogen bonding and weak van der Waals forces. CD and FT-IR results revealed no conformational changes in ct-DNA and t-RNA structure on binding with esculetin. Furthermore, competitive displacement assay with ethidium bromide, melting temperature, viscosity measurement, and potassium iodide quenching experiments, reflected that esculetin probably binds to the minor groove of ct-DNA. The molecular docking results provided further confirmation for the spectroscopic findings, including the binding location of esculetin and binding energies of esculetin complexes with ct-DNA and t-RNA. Molecular dynamics simulation studies demonstrated the conformational stability and flexibility of nucleic acids.

Copper(ii) complexes supported by modified azo-based ligands: Nucleic acid binding and molecular docking studies

Two new copper(ii) complexes [CuL1] (1) and [CuL2] (2) derived from azo-based ligands 2-hydroxy-5-p-tolylazo-benzaldehyde (HL1) and 1-(2-hydroxy-5-p-tolylazo-phenyl)-ethan-one (HL2) were synthesized. These two ligands and their metal complexes were characterized by elemental analysis, nuclear magnetic resonance (1H and 13C), infrared, and UV/Vis spectroscopic techniques. Spectroscopy and other theoretical studies reveal the geometry of copper complexes, and their binding affinity towards nucleic acids are major groove binding.

Synthesis, characterization of ruthenium(II), nickel(II), palladium(II), and platinum(II) triphenylphosphine-based complexes bearing an ONS-donor chelating agent: Interaction with biomolecules, antioxidant, in vitro cytotoxic, apoptotic activity and cell cycle analysis

Four new transition metal complexes, [M(PPh₃)(L)]^.CH₃OH (M = Ni(II) (1), Pd(II) (2)) [Pt (PPh₃)₂(HL)]Cl (3) and [Ru(CO)(PPh₃)₂(L)] (4) (H₂L = 2,4-dihydroxybenzaldehyde-S-methyldithiocarbazate, PPh₃ = triphenylphosphine) have been synthesized and characterized by elemental analyses (C, H, N), FTIR, NMR (¹H, ³¹P), ESI-MS and UV-visible spectroscopy. The molecular structure of (1) and (2) complexes was confirmed by single-crystal X-ray crystallography. It showed a distorted square planar geometry for both complexes around the metal center, and the H₂L adopt a bi-negative tridentate chelating mode. The interaction with biomolecules viz., calf thymus DNA (ct DNA), yeast RNA (tRNA), and BSA (bovine serum albumin) was examined by both UV-visible and fluorescence spectroscopies. The antioxidant activity of all compounds is discussed on basis of DPPH^• (2,2-diphenyl-1-picrylhydrazyl) scavenging activity and showed better antioxidant activity for complexes compared to the ligand. The in vitro cytotoxicity of the compounds was tested on human (breast cancer (MCF7), colon cancer (HCT116), liver cancer (HepG2), and normal lung fibroblast (WI38)) cell lines, showing that complex (1) the most potent against MCF7 and complex (4) against HCT116 cell lines based on IC₅₀ and selective indices (SI) values. So, both complexes were chosen for further studies such as DNA fragmentation, cell apoptosis, and cell cycle analyses. Complex (1) induced MCF7 cell death by cellular apoptosis and arrest cells at S phase. Complex (4) induced HCT116 cell death predominantly by cellular necrosis and arrested cell division at G2/M phase due to DNA damage.

Synthesis, comparative in vitro antibacterial, antioxidant and UV fluorescence studies of bis indole Schiff bases and molecular docking with ct-DNA and SARS-CoV-2 Mpro

In this study, synthesis of 15 novel bis indole-based Schiff bases (SBs) 4a-4o was conducted by condensation of 2-(1-aminobenzyl)benzimidazole with symmetrical bis-isatins linked via five alkyl chains (n = 2-6). These were subjected to ADME (absorption, distribution, metabolism and excretion), physiochemical properties, molecular docking, in vitro antibacterial and antioxidant studies. The in silico studies indicated lower toxicity with metabolic stability for nearly all the derivatives proving reliability as drug candidates. The comparative antibacterial study against Staphylococcus aureus and Escherichia coli, also showed a superior inhibition than reference drug and their mono counterparts. The increase in linker alkyl chain length and variation of substituents in indole, further predicted increased inhibition, with maximum value for compound 4o at 50 μg/ml. The in vitro calf thymus DNA (ct-DNA) binding ability of compounds 4c, 4f, 4i, 4l, 4 m, 4n, and 4o was evaluated via ultraviolet-visible and fluorescence spectroscopy techniques. A hyperchromic effect was observed with no apparent wavelength shift which predicted for the groove binding mode. A moderate binding constant for 4o, in fluorescence results, confirms groove binding. The molecular docking of 4o with ct-DNA (PDBID:1BNA) and SARS-CoV-2 M^pro (3CL protease, PDBID:6LU7) prove its efficacy as potential DNA binder and antiviral agent.

Identification of Unique Quinazolone Thiazoles as Novel Structural Scaffolds for Potential Gram-Negative Bacterial Conquerors

A class of quinazolone thiazoles was identified as new structural scaffolds for potential antibacterial conquerors to tackle dreadful resistance. Some prepared compounds exhibited favorable bacteriostatic efficiencies on tested bacteria, and the most representative 5j featuring the 4-trifluoromethylphenyl group possessed superior performances against Escherichia coli and Pseudomonas aeruginosa to norfloxacin. Further studies revealed that 5j with inappreciable hemolysis could hinder the formation of bacterial biofilms and trigger reactive oxygen species generation, which could take responsibility for emerging low resistance. Subsequent paralleled exploration discovered that 5j not only disintegrated outer and inner membranes to induce leakage of cytoplasmic contents but also broke the metabolism by suppressing dehydrogenase. Meanwhile, derivative 5j could intercalate into DNA to exert powerful antibacterial properties. Moreover, compound 5j gave synergistic effects against some Gram-negative bacteria in combination with norfloxacin. These findings indicated that this novel structural type of quinazolone thiazoles showed therapeutic foreground in struggling with Gram-negative bacterial infections.