Cu(II) complex with auxin (3-indoleacetic acid) and an aromatic planar ligand: synthesis, crystal structure, biomolecular interactions and radical scavenging activity

Heterocyclic (pyrazine)carboxamide Ru(ii) complexes: structural, experimental and theoretical studies of interactions with biomolecules and cytotoxicity

Treatments of N-(1H-benzo[d]imidazol-2-yl)pyrazine-2-carboxamide (HL1) and N-(benzo[d]thiazol-2-yl)pyrazine-2-carboxamide carboxamide ligands (HL2) with [Ru(p-cymene)Cl2]2 and [Ru(PPh3)3Cl2] precursors afforded the respective Ru(ii) complexes [Ru(L1)(p-cymene)Cl] (Ru1), [Ru(L2)(p-cymene)Cl] (Ru2), [Ru(L1)(PPh3)2Cl] (Ru3), and [Ru(L2)(PPh3)2Cl] (Ru4). These complexes were characterized by NMR, FT-IR spectroscopies, mass spectrometry, elemental analyses, and crystal X-ray crystallography for Ru2. The molecular structure of complex Ru2 contains one mono-anionic bidentate bound ligand and display pseudo-octahedral piano stool geometry around the Ru(ii) atom. The interactions with calf thymus DNA (CT-DNA) and bovine serum albumin (BSA) were investigated by spectroscopic techniques. The experimental binding studies suggest that complexes Ru1-Ru4 interact with DNA, primarily through minor groove binding, as supported by molecular docking results. Additionally, these complexes exhibit strong quenching of the fluorescence of tryptophan residues in BSA, displaying static quenching. The in vitro cytotoxicity studies of compounds Ru1-Ru4 were assessed in cancer cell lines (A549, PC-3, HT-29, Caco-2, and HeLa), as well as a non-cancer line (KMST-6). Compounds Ru1 and Ru2 exhibited superior cytotoxicity compared to Ru3 and Ru4. The in vitro cytotoxicity and selectivity of compounds Ru1 and Ru2 against A549, PC-3, and Caco-2 cell lines surpassed that of cisplatin.

Aminoquinoline-based Re(I) tricarbonyl complexes: Insights into their antiproliferative activity and mechanisms of action

In an effort to develop new potent anticancer agents, two Schiff base rhenium(I) tricarbonyl complexes, containing the ubiquitous aminoquinoline scaffold, were synthesized. Both aminoquinoline ligands and Re(I) complexes showed adequate stability over a 48-h incubation period. Furthermore, the cytotoxic activity of the precursor ligands and rhenium(I) complexes were evaluated against the hormone-dependent MCF-7 and hormone-independent triple negative MDA-MB-231 breast cancer cell lines. Inclusion of the [Re(CO)3Cl]+ entity significantly enhanced the cytotoxicity of the aminoquinoline Schiff base ligands against the tested cancer cell lines. Remarkably, the incorporation of the Schiff-base iminoquinolyl entity notably enhanced the cytotoxic activity of the Re(I) complexes, in comparison with the iminopyridyl entity. Notably, the quinolyl-substituted complex showed up to three-fold higher activity than cisplatin against breast cancer cell lines, underpinning the significance of the quinoline pharmacophore in rational drug design. In addition, the most active Re(I) complex showed better selectivity towards the breast cancer cells over non-tumorigenic FG-0 cells. Western blotting revealed that the complexes increased levels of γH2AX, a key DNA damage response protein. Moreover, apoptosis was confirmed in both cell lines due to the detection of cleaved PARP. The complexes show favourable binding affinities towards both calf thymus DNA (CT-DNA), and bovine serum albumin (BSA), and the order of their interactions align with their cytotoxic effects. The in silico molecular simulations of the complexes were also performed with CT-DNA and BSA targets.

Synthesis and characterization of the new ligand, 1,2,4-triazino[5,6-b]indol-3-ylimino methyl naphthalene-2-ol and its Ni(II) and Cu(II) complexes: comparative studies of their in vitro DNA and HSA Binding

A new ligand 1,2,4-triazino[5,6-b]indol-3-ylimino methyl naphthalene-2-ol (HL) was derived from 5H-[1,2,4]triazino[5,6-b]indol-3-amine and 2-hydroxy-1-naphthaldehyde. The metal complexes of the type [Ni(L)(Bipy)]1/2SO₄ (1), [Cu(L)(Bipy)(H₂O)₂]1/2SO₄ (2), [Ni(L)(Phen)]1/2SO₄ (3) and [Cu(L)(Phen)(H₂O)₂]1/2SO₄ (4) were synthesized. The ligand (HL) and complexes 1-4 were thoroughly characterized by elemental analysis and spectroscopic methods (FT-IR, ToF-MS, ¹H NMR, ¹³C NMR), molar conductance and magnetic moment determination. The Ni(II) complexes 1 and 3 adopt the square planar geometry and Cu(II) complexes 2 and 4 acquire distorted octahedral arrangement. In vitro DNA binding behavior of ligand (HL) and metal complexes 1-4 was explored by fluorescence spectral and ethidium bromide studies. The outcomes reveal that the complexes interact with DNA via non-covalent groove binding and electrostatic interactions. The higher binding constant (K) values of 4.35 × 10⁴ and 9.12 × 10⁴ M^-1 for complexes 2 and 4 indicate stronger binding ability with DNA. Moreover, in vitro human serum albumin (HSA) binding experiment with HL and complexes 1-4 reveals conformational modulations in the Trp-214 microenvironments in the subdomain IIA pocket.

Enhancing the biological properties of zinc complexes with bis(indolyl)methane groups: Synthesis, characterization, DNA interaction, and biocide activity

The unprecedented mononucleated ligand (6,6-di(1H-indol-3-yl)-N,N-bis(pyridin-2-ylmethyl)hexan-1-amine (L^C5) with an N₃-donor set and its complexes [Zn(L^C5)Cl₂] • 2CH₃OH (1) and [Zn(L^C5)₂](ClO₄)₂ (2), were successfully prepared. All compounds were fully characterized by a suite of physicochemical methods. Fluid ¹H and ¹³C NMR spectroscopy, as well as DFT and TD-DFT calculations, were carried out to propose a viable structural arrangement for both complexes. The interaction between these compounds and DNA was monitored in the UV region where binding constants (K_b) were estimated (2 > 1 > L^C5). These data were corroborated by DNA cleavage assays using groove binders, circular dichroism, and docking studies. Both complexes confirmed their biocide activity against selected microorganisms: Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria, the filamentous fungi A. fumigatus and S. cerevisiae. Finally, the cytotoxic activities of 1 and 2 were tested against the erythroleukemia K562 cell line. For all biological studies, it was probed that the presence of the indole moieties and the zinc atoms in the chemical composition of the complexes studied could increase the magnitude of the activity following the order: 2 > 1 > L^C5, where a linear relationship between the biological activity upon K562 cells (IC₅₀) and DNA binding studies (K_b) was found.

Synthesis, substitution kinetics, DNA/BSA binding and cytotoxicity of tridentate N^E^N (E = NH, O, S) pyrazolyl palladium(II) complexes

The pincer complexes, [Pd(L₁)Cl]BF₄ (PdL₁), [Pd(L₂)Cl]BF₄ (PdL₂), [Pd(L₃)Cl]BF₄ (PdL₃), [Pd(L₄)Cl]BF₄ (PdL₄) were prepared by reacting the corresponding ligands, 2,6-bis[(1H-pyrazol-1-yl)methyl]pyridine (L₁), bis[2-(1H-pyrazol-1-yl)ethyl]amine (L₂), bis[2-(1H-pyrazol-1-yl)ethyl]ether (L₃), and bis[2-(1H-prazol-1-yl)ethyl]sulphide (L₄) with [PdCl₂(NCMe)]₂ in the presence NaBF₄. The solid-state structures of complexes PdL₁-PdL₄ confirmed a tridentate coordination mode, with one chloro ligand completing the coordination sphere to afford square-planar complexes. Chemical behaviour of the complexes in solution confirms their stability in both aqueous and DMSO stock media. The electrochemical properties of the compounds showed irreversible two-electron reduction process. Kinetic reactivity of Pd complexes with the biological nucleophiles viz, thiourea (Tu), L-methionine (L-Met) and guanosine 5'-diphosphate disodium salt (5'-GMP) followed the order: PdL₂ < PdL₃ < PdL₄, and PdL₂ < PdL₁. The kinetic reactivity is subject to the electronic effects of the spectator ligand(s), and the trend was supported by the DFT computed results. The palladium complexes PdL₁-PdL₄ bind to calf thymus (CT-DNA) via intercalation mode. In addition, the bovine serum albumin (BSA) showed good binding affinity to the complexes. The mode of quenching mechanism of the intrinsic fluorescence of CT-DNA and BSA by the complexes was found to be static. The order of interactions of the complexes with DNA and BSA was in tandem with the rate of substitution kinetics. The complexes, however, displayed relatively low cytotoxicity (IC₅₀ > 100 µM) when tested against the human cervical adenocarcinoma (HeLa) cell line and the transformed human lung fibroblast cell line (MRC-5 SV2).

The Cytotoxic Effect of Copper (II) Complexes with Halogenated 1,3-Disubstituted Arylthioureas on Cancer and Bacterial Cells

A series of eight copper (II) complexes with 3-(4-chloro-3-nitrophenyl)thiourea were designed and synthesized. The cytotoxic activity of all compounds was assessed in three human cancer cell lines (SW480, SW620, PC3) and human normal keratinocytes (HaCaT). The complexes 1, 3, 5, 7 and 8 were cytotoxic to the studied tumor cells in the low micromolar range, without affecting the normal cells. The complexes 1, 3, 7 and 8 induced lactate dehydrogenase (LDH) release in all cancer cell lines, but not in the HaCaT cells. They provoked early apoptosis in pathological cells, especially in SW480 and PC3 cells. The ability of compounds 1, 3, 7 and 8 to diminish interleukin-6 (IL-6) concentration in a cell was established. For the first time, the influence of the most promising Cu (II) complexes on intensities of detoxifying and reactive oxygen species (ROS) scavenging the enzymes of tumor cells was studied. The cytotoxic effect of all copper (II) conjugates against standard and hospital bacterial strains was also proved.