New mixed ligand copper(II) hydrazone‐based complexes: Synthesis, characterization, crystal structure, DNA/RNA/BSA binding, in vitro anticancer, apoptotic activity, and cell cycle analysis

Palladium(ii), platinum(ii), and silver(i) complexes with 3-acetylcoumarin benzoylhydrazone Schiff base: Synthesis, characterization, biomolecular interactions, cytotoxic activity, and computational studies

New Pd(ii) (C1), Pt(ii) (C2), and Ag(i) (C3) complexes derived from 3-acetylcoumarin benzoylhydrazone (HL) Schiff base were synthesized and characterized by FTIR, 1H NMR, UV-visible spectroscopies along with elemental analysis (C, H, N), magnetic, molar conductivity measurements, and DFT calculations. The obtained results suggested that the ligand had different behaviors in the complexes: mono-negative tridentate (C1) and neutral tridentate (C2) as an ONO-donor and neutral bidentate (C3) as an ON-donor. Quantum chemistry calculations were performed to validate the stability of the suggested geometries and indicated that all the complexes possess tetra-coordinated metal ions. The binding affinity of all the compounds toward calf thymus (ctDNA), yeast (tRNA), and bovine serum albumin (BSA) was evaluated by absorption/emission spectral titration studies, which revealed the intercalative binding to ctDNA and tRNA and static binding upon complex formation with BSA. Molecular insights into the binding affinity of the characterized complexes were provided through conducting molecular docking analysis. Moreover, the cytotoxic activity (in vitro) of the compounds was screened against human cancerous cell lines and a non-cancerous lung fibroblast (WI38) one using cis-platin as a reference drug. The IC50 and selective index (SI) values indicated the higher cytotoxic activity of all the metal complexes compared to their parent ligand. Among all the compounds, the complex C2 showed the highest activity. These results confirmed the improvement of the anticancer activity of the ligand by incorporating the metal ions. In addition, flow cytometry results showed that complexes C1 and C2 induced cell cycle arrest at S and G1/S, respectively.

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.

Bimetallic bis-Aroyldihydrazone-Isatin Complexes of High O=V(IV) and Low Cu(II) Valent Ions as Effective Biological Reagents for Antimicrobial and Anticancer Assays

Due to the versatile bioreactivity of aroyldihydrazone complexes as cost-effective alternatives with different transition metals, two novel bimetallic homo-complexes (VOLph and CuLph) were prepared via the coordination of a terephthalic dihydrazone diisatin ligand (H2Lph) with VO2+ and Cu2+ ions, respectively. The structure elucidation was confirmed by alternative spectral methods. Biologically, the H2Lph ligand and its MLph complexes (M2+ = VO2+ or Cu2+) were investigated as antimicrobial and anticancer agents. Their biochemical activities towards ctDNA (calf thymus DNA) were estimated using measurable titration viscometrically and spectrophotometrically, as well as the gel electrophoresis technique. The growth inhibition of both VOLph and CuLph complexes against microbial and cancer cells was measured, and the inhibition action, MIC, and IC50 were compared to the inhibition action of the free H2Lph ligand. Both VOLph and CuLph showed remarkable interactive binding with ctDNA compared to the free ligand H2Lph, based on Kb = 16.31, 16.04 and 12.41 × 107 mol-1 dm3 and ΔGb≠ = 47.11, -46.89, and -44.05 kJ mol-1 for VOLph, CuLph, and H2Lph, respectively, due to the central metal ion (VIVO and CuII ions). VOLph (with a higher oxidation state of the V4+ ion and oxo-ligand) exhibited enhanced interaction with the ctDNA molecule compared to CuLph, demonstrating the role and type of the central metal ion within the performed electronegative and electrophilic characters.

Electronic and ring size effects of N-heterocyclic carbenes on the kinetics of ligand substitution reactions and DNA/protein interactions of their palladium(II) complexes

The synthesis, substitution kinetics and DNA/BSA interactions of four cationic Pd(II) complexes [Pd(1)Cl]BF4 (Pd1), [Pd(2)Cl]BF4 (Pd2), [Pd(3)Cl]BF4 (Pd3) and [Pd(4)Cl]BF4 (Pd4), derived from the reaction of [PdCl2(NCCH3)2] with ligands 2,6-bis(3-methylimidazolium-1-yl)pyridine dibromide (1), 2,6-bis(3-ethylimidazolium-1-yl)pyridine dibromide (2), 2,6-bis(1-methylimidazole-2-thione)pyridine (3), and 2,6-bis(1-ethylimidazole-2-thione)pyridine (4), respectively are reported. The complexes were characterised by various spectroscopic techniques and single crystal X-ray diffraction for compound Pd2. Kinetic reactivity of the complexes with the biologically relevant nucleophiles thiourea (Tu), L-methionine (L-Met) and guanosine 5'-monophosphate sodium salt (5'-GMP) was in the order: Pd1 > Pd2 > Pd3 > Pd4, which was largely dependent on the electronic and ring size of the chelate ligands, consistent with Density functional theory (DFT) simulations. The interactions of the complexes with calf thymus DNA (CT-DNA) and bovine serum albumin (BSA) binding titrations showed strong binding. Both the experimental and in silico data reveal CT-DNA intercalative binding mode.

Bioreactivity of divalent bimetallic vanadyl and zinc complexes bis-oxalyldihydrazone ligand against microbial and human cancer series. ctDNA interaction mode

Two novel divalent bimetallic complexes were constructed from the complexation of O=V4+ and Zn2+ ions (VOL and ZnL), respectively, with diisatin oxalyldihydrazone ligand (H2L). Various spectroscopic tools were used to confirm their chemical structures (FT-IR, NMR, EI-Mass, and electronic spectra), besides, elemental analyses and conductivity features. To estimate the role of divalent metal ions in their coordination compound for developing their bio-reactivity, the free ligand H2Lox, and its complexes (VOL and ZnL) were employed spectroscopic investigations against the growth of some microbial series (fungi and bacteria) and also against three human cancer/normal cells. Furthermore, their interaction behavior against calf thymus DNA (ctDNA) was studied through viscometric and spectrophotometric studies to discover the role of O=V4+ and Zn2+ ions to determine the mode of binding with ctDNA. The inhibiting effect of H2L, VOL, and ZnL versus the titled microbial (bacterial and fungal) was built upon their inhibited zone areas in mm and the MIC concentrations in μM. Their action against the three human cancer cells' growth was evaluated by IC50 values in μM and the selectivity index in percentage. Both VOL and ZnL complexes exhibited an amazing series with three human cancer cell growth (according to the zone values in mm of inhibition, MIC in μM, and IC50 values in μM) compared to those of their uncoordinated H2L ligand. VOL demonstrated a distinguished interacting behavior with ctDNA more than that interaction of ZnL depending on the variation of the central metal ion chemical features. Within the covalent and non-covalent interaction modes, the interaction binding between H2L, VOL, and ZnL with ctDNA was discussed based on the electronic spectroscopic observation.

Copper (II) Species with Improved Anti-Melanoma and Antibacterial Activity by Inclusion in β-Cyclodextrin

To improve their biological activity, complexes [Cu(bipy)(dmtp)₂(OH₂)](ClO₄)₂·dmtp (1) and [Cu(phen)(dmtp)₂(OH₂)](ClO₄)₂·dmtp (2) (bipy 2,2'-bipyridine, phen: 1,10-phenantroline, and dmtp: 5,7-dimethyl-1,2,4-triazolo [1,5-a]pyrimidine) were included in β-cyclodextrins (β-CD). During the inclusion, the co-crystalized dmtp molecule was lost, and UV-Vis spectra together with the docking studies indicated the synthesis of new materials with 1:1 and 1:2 molar ratios between complexes and β-CD. The association between Cu(II) compounds and β-CD has been proven by the identification of the components' patterns in the IR spectra and powder XRD diffractograms, while solid-state UV-Vis and EPR spectra analysis highlighted a slight modification of the square-pyramidal stereochemistry around Cu(II) in comparison with precursors. The inclusion species are stable in solution and exhibit the ability to scavenge or trap ROS species (O₂·^- and HO·) as indicated by the EPR experiments. Moreover, the two inclusion species exhibit anti-proliferative activity against murine melanoma B16 cells, which has been more significant for (2)@β-CD in comparison with (2). This behavior is associated with a cell cycle arrest in the G0/G1 phase. Compared with precursors, (1a)@β-CD and (2a)@β-CD exhibit 17 and 26 times more intense activity against planktonic Escherichia coli, respectively, while (2a)@β-CD is 3 times more active against the Staphylococcus aureus strain.

Crystal structure, in vitro cytotoxicity, DNA binding and DFT calculations of new copper (II) complexes with coumarin-amide ligand

This work describes the synthesis, anticancer activity and electron structure study of two Cu (II) complexes with coumarin-3-formyl-(3-(aminomethyl) pyridine) ligand (L) - C1 (Cu₂L₂(OAc)₄) and C2 (CuL₂(NO₃)₂). The structure of C1 and C2 was confirmed by elemental analysis, FTIR, and single-crystal X-ray analysis. Complex C1 crystallizes as binuclear where two Cu (II) ions are bridged by four acetate ligands while C2 is a mononuclear complex with twisted octahedral geometry. Density functional theory (DFT) calculations revealed that electronic transitions originate from metal-ligand charge transfer and d-d transitions of metal ions. According to the results of UV-Vis and fluorescence titrations, C1 and C2 intercalate with DNA with the binding constants of 6.9 × 10⁵ M^-1 and 5.9 × 10⁵ M^-1, respectively. The in vitro cytotoxicity assays on four cancer cell lines (HeLa, HepG2, MCF-7 and A549) and a normal HUVEC cell line indicated higher anti-MCF-7 activity of C2 compared with cisplatin (IC₅₀ = 2.86 ± 0.08 μM vs. 9.07 ± 0.10 μM). Moreover, C2 had superior selectivity since IC₅₀ toward HUVEC cells was over 150 μM compared with 0.58 ± 0.05 μM for cisplatin. We concluded that the anti-MCF activity of mononuclear C2 complex is better than that of binuclear C1 and cisplatin. Therefore, C2 has been selected as a hit compound to develop novel non‑platinum anticancer agents through modification of coumarin-amide structure and variation of copper (II) salts.

Antiproliferative Copper(II) Complexes Bearing Mixed Chelating Ligands: Structural Characterization, ROS Scavenging, In Silico Studies, and Anti-Melanoma Activity

Melanoma is a skin cancer characterized by rapid growth and spread for which current therapies produce both resistance and increased risk of infection. To develop new anti-melanoma biocompatible species, the series of complexes Cu(N-N)(bzac)(X)⋅nH₂O (N-N: 1,10-phenanthroline/2,2′-bipyridine, Hbzac: 1-phenyl-1,3-butanedione, X: NO₃/ClO₄, and n = 0, 1) was studied. Single-crystal X-ray diffraction revealed a mononuclear structure for all complexes. The ability of the complexes to scavenge or trap reactive oxygen species such as O₂⋅⁻ and HO⋅ was proved by EPR spectroscopy experiments. All complexes inhibited B16 murine melanoma cells in a dose-dependent and nanomolar range, but the complexes with 1,10-phenanthroline were more active. Moreover, comparative activity on B16 and healthy BJ cells revealed a therapeutic index of 1.27–2.24. Bioinformatic methods were used to calculate the drug-likeness, pharmacokinetic, pharmacogenomic, and pharmacodynamic profiles of the compounds. The results showed that all compounds exhibit drug-likeness features, as well as promising absorption, distribution, metabolism, and excretion (ADME) properties, and no toxicity. The pharmacodynamics results showed that the neutral species appear to be good candidates for antitumor molecular targets (Tyrosyl-DNA phosphodiesterase 1, DNA-(apurinic or apyrimidinic site) lyase or Kruppel-like factor 5). Furthermore, the pharmacogenomic results showed a good affinity of the copper(II) complexes for the human cytochrome. These results recommend complexes bearing 1,10-phenanthroline as good candidates for developing drugs to melanoma alternative treatment.

Sparfloxacin - Cu(II) - aromatic heterocyclic complexes: synthesis, characterization and in vitro anticancer evaluation

Two new copper(II) complexes of sparfloxacin (sf), [Cu(Hsf)(HPB)(H₂O)](ClO₄)₂ (1) and [Cu(Hsf)(PBT)(H₂O)](ClO₄)₂ (2) (where HPB = 2-(2'-pyridyl)benzimidazole and PBT = 2-(4'-pyridyl) benzothiazole), have been synthesized and characterized by physicochemical and spectroscopic techniques. The oil-water partition coefficient (log P) values of complexes 1 and 2 were 1.47 and 1.71, respectively. By studying the interaction between the complexes and DNA, it was found that the complexes could bind to DNA through an intercalation mode. Moreover, both complexes were evaluated for antitumor activity, revealing that the complexes displayed good inhibitory activity toward the tested cancer cell lines (human lung carcinoma A549 cells, human hepatocellular carcinoma Bel-7402 cells and human esophageal carcinoma Eca-109 cells), but showed relatively low toxicity against normal human hepatic LO2 cells. In particular, the antitumor mechanism of the complexes on Eca-109 cells was investigated by morphological analysis, apoptosis analysis and determination of cell cycle arrest, mitochondrial membrane potential, reactive oxygen species (ROS) levels, and release of cytochrome c and Ca²⁺. The results demonstrated that the complexes could induce loss of intracellular mitochondrial functions and increase of ROS levels, which led to an increase of Ca²⁺ levels and the release of cytochrome c into the cytoplasm. In addition, the cell cycle was arrested in the G2/M phase, and western blot analysis showed that the caspase family was activated. These results fully proved that the complexes could induce apoptosis through DNA damage and loss of mitochondrial functions, accompanied by the regulation of endogenous proteins.