Second generation of Casiopeinas®: A joint experimental and theoretical study

Recently Reported Biological Activities and Action Targets of Pt(II)- and Cu(II)-Based Complexes

Most diseases that affect human beings across the world are now treated with drugs of organic origin. However, some of these are associated with side effects, toxicity, and resistance phenomena. For the treatment of many illnesses, the development of new molecules with pharmacological potential is now an urgent matter. The biological activities of metal complexes have been reported to have antitumor, antimicrobial, anti-inflammatory, anti-infective and antiparasitic effects, amongst others. Metal complexes are effective because they possess unique properties. For example, the complex entity possesses the effective biological activity, then the formation of coordination bonds between the metal ions and ligands is controlled, metal ions provide it with extraordinary mechanisms of action because of characteristics such as d-orbitals, oxidation states, and specific orientations; metal complexes also exhibit good stability and good physicochemical properties such as water solubility. Platinum is a transition metal widely used in the design of drugs with antineoplastic activities; however, platinum is associated with side effects which have made it necessary to search for, and design, novel complexes based on other metals. Copper is a biometal which is found in living systems; it is now used in the design of metal complexes with biological activities that have demonstrated antitumoral, antimicrobial and anti-inflammatory effects, amongst others. In this review, we consider the open horizons of Cu(II)- and Pt(II)-based complexes, new trends in their design, their synthesis, their biological activities and their targets of action.

Cu(II) complexes with a salicylaldehyde derivative and α-diimines as co-ligands: synthesis, characterization, biological activity. Experimental and theoretical approach

Copper(II) complexes with an α-diimine show a wide variety of biological activities, such as antibacterial, antifungal, antioxidant and anticancer. In this work, we synthesized and structurally characterized two novel Cu(II) complexes with methyl 3-formyl-4-hydroxybenzoate (HL) and α-diimines: 2,2'-bipyridine (bipy) and 1,10-phenanthroline (phen). Crystal structure analysis shows that the formulas of the compounds are [Cu(bipy)(L)(BF4)] (1) and [Cu(phen)(L)(H2O)](BF4)·H2O (2), with BF4- as a ligand in complex 1, which is rarely coordinated to metals. Both complexes have a square pyramidal geometry, while DFT calculations showed that the most stable structures of complexes 1 and 2 in a water/DMSO mixture are square-planar derivatives [Cu(bipy)(L)]+ and [Cu(phen)(L)]+. The antibacterial activity of compounds was evaluated in vitro on four Gram-negative and four Gram-positive bacterial strains. Complex 2 showed greater antibacterial activity towards all bacterial strains comparable to the control compound Amikacin. Complex 2 exerted a strong cytotoxic effect against the tested cancer cell lines (IC50 values ranging from 0.32 to 0.44 μM). Both complexes caused apoptotic cell death in HeLa cells and a noticeable in vitro antiangiogenic effect. In the concentration range of 5 to 100 μM, the complexes showed the absence of a genotoxic effect and displayed a protective effect against oxidative DNA damage induced by H2O2 in human peripheral blood cells. The interaction between the compounds and calf-thymus DNA was evaluated by diverse techniques suggesting a tight binding, which was also confirmed by molecular docking. In addition, it was found that the complexes bind tightly and reversibly to bovine and human serum albumin.

Structural and solution speciation studies on selected [Cu(NN)(OO)] complexes and an investigation of their biomimetic activity, ROS generation and their cytotoxicity in normoxic, hypoxic and anoxic environments in MCF-7 breast cancer-derived cells

Reactive oxygen species(ROS) generation with subsequent DNA damage is one of the principle mechanisms of action assigned to copper-based anticancer complexes. The efficacy of this type of chemotherapeutic may be reduced in the low oxygen environment of tumours. In this study the cytotoxicity of three complexes, [Cu(dips)(phen)] (1), [Cu(ph)(phen)]·2H2O (2) and [Cu(ph)(bpy)]·H2O (3) (disp: 3,5-diisopropylsalicylate, phen: 1,10- phenanthroline, ph: phthalate, bpy: 2,2'-bipyridyl) were assessed for anticancer activity in the breast-cancer derived MCF-7 line under normoxic, hypoxic and anoxic conditions. In an immortalised keratinocyte HaCaT cell line, the cytotoxicity of complexes 2 and 3 was significantly reduced under both normoxic and hypoxic conditions, whilst the cytotoxicity of complex 1 was increased under hypoxic conditions. The ability of the complexes to generate ROS in the MCF-7 cell line was evaluated as was their ability to act as superoxide dismutase(SOD) and catalase mimics using a yeast cell assay. ROS generation was significant for complexes 2 and 3, less so for complex 1 though all three complexes had SOD mimetic ability. Given the ternary nature of the complexes, solution speciation studies were undertaken but were only successful for complex 3, due to solubility issues with the other two complexes. The concentration distribution of various species, formed in aqueous solution, was evaluated as a function of pH and confirmed that complex 3 is the dominant species at physiological pH in the mM concentration range. However, as its concentration diminishes, it experiences a progressive dissociation, leading to the formation of binary complexes of bpy alongside unbound phthalate.

Organic-inorganic hybrid salt and mixed ligand Cr(III) complexes containing the natural flavonoid chrysin: Synthesis, characterization, computational, and biological studies

Organic-inorganic hybrid salt and mixed ligand Cr(III) complexes (Cr1 and Cr2) containing the natural flavonoid chrysin were synthesized. The metal complexes were characterized using UV-Vis, Fourier-transform infrared, MS, SEM-EDX, XRD, and molar conductance measurements. Based on experimental and DFT/TD-DFT calculations, octahedral geometries for the synthesized complexes were suggested. The powder XRD analysis confirms that the synthesized complexes were polycrystalline, with orthorhombic and monoclinic crystal systems having average crystallite sizes of 21.453 and 19.600 nm, percent crystallinities of 51% and 31.37%, and dislocation densities of 2.324 × 10^-3 and 2.603 × 10^-3 nm^-2 for Cr1 and Cr2, respectively. The complexes were subjected to cytotoxicity, antibacterial, and antioxidant studies. The in vitro biological studies were supported with quantum chemical and molecular docking computational studies. Cr1 showed significant cytotoxicity to the MCF-7 cell line, with an IC₅₀ value of 8.08 μM compared to 30.85 μM for Cr2 and 18.62 μM for cisplatin. Cr2 showed better antibacterial activity than Cr1. The higher E _HOMO (-5.959 eV) and dipole moment (10.838 Debye) values of Cr2 obtained from the quantum chemical calculations support the observed in vitro antibacterial activities. The overall results indicated that Cr1 is a promising cytotoxic drug candidate.

Cytotoxic mixed-ligand complexes of Cu(II): A combined experimental and computational study

Herein, we report the synthesis of mixed-ligand Cu(II) complexes of metformin and ciprofloxacin drugs together with 1,10-phenanthroline as a co-ligand. The synthesized complexes were characterized using different spectroscopic and spectrometric techniques. In vitro cytotoxic activity against human breast adenocarcinoma cancer cell line (MCF-7) as well as antibacterial activity against two gram-negative and two gram-positive bacterial strains were also investigated. The analyses of the experimental results were supported using quantum chemical calculations and molecular docking studies against estrogen receptor alpha (ERα; PDB: 5GS4). The cytotoxicity of the [Cu(II) (metformin) (1,10-phenanthroline)] complex (1), with IC₅₀ of 4.29 µM, and the [Cu(II) (ciprofloxacin) (1,10-phenanthroline)] complex (2), with IC₅₀ of 7.58 µM, were found to be more effective than the referenced drug, cisplatin which has IC₅₀ of 18.62 µM against MCF-7 cell line. The molecular docking analysis is also in good agreement with the experimental results, with binding affinities of –7.35, –8.76 and –6.32 kcal/mol, respectively, for complexes 1, 2 and cisplatin against ERα. Moreover, complex 2 showed significant antibacterial activity against E. coli (inhibition diameter zone, IDZ, = 17.3 mm), P. aeruginosa (IDZ = 17.08 mm), and S. pyogen (IDZ = 17.33 mm), at 25 μg/ml compared to ciprofloxacin (IDZ = 20.0, 20.3, and 21.3 mm), respectively. Our BOILED-egg model indicated that the synthesized metal complexes have potentially minimal neurotoxicity than that of cisplatin.

Casiopeinas® third generation, with indomethacin: synthesis, characterization, DFT studies, antiproliferative activity, and nanoencapsulation

Seven new Casiopeinas® were synthesized and properly characterized. These novel compounds have a general formula [Cu(N-N)(Indo)]NO3, where Indo is deprotonated indomethacin and N-N is either bipyridine or phenanthroline with some methyl-substituted derivatives, belonging to the third generation of Casiopeinas®. Spectroscopic characterization suggests a square-based pyramid geometry and voltammetry experiments indicate that the redox potential is strongly dependent on the N-N ligand. All the presented compounds show high cytotoxic efficiency, and most of them exhibit higher efficacy compared to the well-known cisplatin drug and acetylacetonate analogs of the first generation. Computational calculations show that antiproliferative behavior can be directly related to the volume of the molecules. Besides, a chitosan (CS)-polyacrylamide (PNIPAAm) nanogel was synthesized and characterized to examine the encapsulation and release properties of the [Cu(4,7-dimethyl-1,10-phenanthroline)(Indo)]NO3 compound. The results show good encapsulation performance in acidic conditions and a higher kinetic drug release in acidic media than at neutral pH. This result can be described by the Peppas-Sahlin model and indicates a release mechanism predominantly by Fick diffusion.

Casiopeinas of Third Generations: Synthesis, Characterization, Cytotoxic Activity and Structure-Activity Relationships of Mixed Chelate Compounds with Bioactive Secondary Ligands

Casiopeinas are a family of copper(II) coordination compounds that have shown an important antineoplastic effect and low toxicity in normal cells. These compounds induce death cells by apoptosis through a catalytic redox process with endogenous reducing agents. Further studies included a structural variation, improving the activity and selectivity in cancer cells or other targets. In the present work we report the third generation, which contains a bioactive monocharged secondary ligand, as well as the design, synthesis, characterization and antiproliferative activity, of sixteen new copper(II) coordination compounds with curcumin or dimethoxycurcumin as secondary ligands. All compounds were characterized by elemental analysis, FTIR, UV-Vis, magnetic susceptibility, mass spectra with MALDI-flight time, cyclic voltammetry, electron paramagnetic resonance (EPR) spectroscopy and X-ray diffraction. Crystallization of two complexes was achieved in dimethylsulfoxide (DMSO) with polar solvent, and crystal data demonstrated that a square-based or square-base pyramid geometry are possible. A 1:1:1 stoichiometry (diimine: copper: curcuminoid) ratio and the possibility of a nitrate ion as a counterion were supported. ¹H, ¹³C NMR spectra were used for the ligands. A sulforhodamine B assay was used to evaluate the cytotoxicity effect against two human cancer cell lines, SKLU-1 and HeLa. Electronic descriptors and redox potential were obtained by DFT calculations. Structure–activity relationships are strongly determined by the redox potential (E_1/2) of copper(II) and molar volume (V) of the complexes. These compounds can be used as a template to open a wide field of research both experimentally and theoretically.

Casiopeinas® as SARS-CoV-2 main protease (Mpro) inhibitors: a combined DFT, molecular docking and ONIOM approach

Computational combined protocols suggest that Casiopeinas can block the active site of Mpro SARS-CoV-2 by binding to its main amino acids.

Heteroleptic copper(II) complexes of prenylated flavonoid osajin behave as selective and effective antiproliferative and anti-inflammatory agents

Heteroleptic copper(II) complexes, containing prenylated flavonoid osajin isolated from the fruits of Maclura pomifera Schneid., were prepared and thoroughly characterized, including single crystal X-ray analysis. Some of the following complexes of the general composition [Cu(L)(bpy)]NO₃ (1), [Cu(L)(dimebpy)]NO₃·2MeOH (2) [Cu(L)(phen)]NO₃·H₂O (3), [Cu(L)(bphen)]NO₃ (4) and [Cu(L)(dppz)]NO₃ (5), where HL stands for 3-(4-hydroxyphenyl)-5-hydroxy-8,8-dimethyl-6-(3-methylbut-2-ene-1-yl)-4H,8H-benzo[1,2-b:3,4-b']dipyran-4-one (osajin), bpy = 2,2'-bipyridine, dimebpy = 4,4'-dimethyl-2,2'-bipyridine, phen = 1,10-phenanthroline, bphen = 4,7-diphenyl-1,10-phenanthroline and dppz = dipyrido[3,2-a:2',3'-c]phenazine, were also monitored for their solution stability and interactions with cysteine and glutathione by mass spectrometry. The in vitro cytotoxicity of the complexes was evaluated against a panel of eight human cancer cell lines: (MCF-7, HOS, A549, PC-3, A2780, A2780R, Caco-2, and THP-1). The results revealed high antiproliferative activity of the complexes with the best IC₅₀ values of 0.5-3.4 μM for complexes (4) and (5), containing the bulkier N,N'-donor ligands (bphen, and dppz, respectively). The complexes also revealed a relatively low toxicity towards human hepatocytes (IC₅₀ values are higher than 100 μM in some cases), and thus proved to be highly selective towards the cancer cells. On the other hand, the complexes showed a strong in vitro nuclease effect using the model pUC-19 plasmid. In the model of lipopolysaccharide-stimulated (LPS) THP-1 monocytes, the complexes revealed ability to lower the activity of nuclear factor kappa-B/activator protein 1 (NF-κB /AP-1) system and decrease the secretion of tumor necrosis factor alpha (TNF-α). Thus, the complexes have been identified as strong antiproliferative and anti-inflammatory compounds.

Ternary Copper Complex of L-Glutamine and Phenanthroline as Counterions of Cyclo-Tetravanadate Anion: Experimental–Theoretical Characterization and Potential Antineoplastic Activity

Over the last decade, therapeutic metallodrugs have become substantially effective in the treatment of cancer. Thus, developing new effective anticancer drugs is a significant research area against the continuing increase in cancers worldwide. In the search for heterobimetallic prodrugs containing V/Cu, a new cyclo-tetravanadate was synthesized and characterized by UV-visible and FTIR spectroscopies and single-crystal X-ray diffraction. L-Glutamine and 1,10-phenanthroline allow the crystallization of [Cu(L-Gln)(phen)(H2O)]4[V4O12]∙8(H2O) (1), in which the cyclo-tetravanadate acts as a free anion. Density functional theory (DFT) calculations were carried out to characterize the frontier molecular orbitals and molecular electrostatic potential. Global reactivity indexes were calculated and analyzed to give insight into the cyclo-tetravanadate anion and complex counterions interactions. Also, using Bader’s theory of atoms in molecules (AIM), non-covalent interactions were analyzed. Docking analysis with the Casiopeina-like complex resulting from the hydrolysis of compound 1 provided insights into these complex potential anticancer activities by interacting with DNA/tRNA via H-bonds and hydrophobic interactions. The release of both components could act together or separately, acting as prodrugs with potential dual antineoplastic activities.