Ruthenium(III) dimethyl sulfoxide pyridinehydroxamic acid complexes as potential antimetastatic agents: synthesis, characterisation and in vitro pharmacological evaluation

Indazole-Derived Mono-/Diruthenium and Heterotrinuclear Complexes: Switchable Binding Mode, Electronic Form, and Anion Sensing Events

The article deals with the newer classes of mononuclear: [(acac)₂Ru^III(H-Iz)(Iz^-)] 1, [(acac)₂Ru^III(H-Iz)₂]ClO₄ [1]ClO₄/[1']ClO₄, and [(bpy)₂Ru^II(H-Iz)(Iz^-)]ClO₄ [2]ClO₄, mixed-valent unsymmetric dinuclear: [(acac)₂Ru^III(μ-Iz^-)₂Ru^II(bpy)₂]ClO₄ [3]ClO₄, and heterotrinuclear: [(acac)₂Ru^III(μ-Iz^-)₂M^II(μ-Iz^-)₂Ru^III(acac)₂] (M = Co:4a, Ni:4b, Cu:4c, and Zn:4d) complexes (H-Iz = indazole, Iz^- = indazolate, acac = acetylacetonate, and bpy = 2,2'-bipyridine). Structural characterization of all the aforestated complexes established their molecular identities including varying binding modes (N_a and N_b donors and 1H-indazole versus 2H-indazole) of the heterocyclic H-Iz/Iz^- in the complexes. Unlike [1']ClO₄ containing two NH protons at the backface of H-Iz units, the corresponding [1]ClO₄ was found to be unstable due to the deprotonation of its positively charged quaternary nitrogen center, and this resulted in the eventual formation of the parent complex 1. A combination of experimental and density functional theory calculations indicated the redox noninnocent feature of Iz^- in the complexes along the redox chain. The absence of intervalence charge transfer transition in the near-infrared region of the (Iz^-)₂-bridged unsymmetric mixed-valent Ru^IIIRu^II state in [3]ClO₄ suggested negligible intramolecular electronic coupling corresponding to a class I setup (Robin and Day classification). Heterotrinuclear complexes (4a-4d) exhibited varying spin configurations due to spin-spin interactions between the terminal Ru(III) ions and the central M(II) ion. Though both [3]ClO₄ and 4a-4d displayed ligand (Iz^-/Iz^•)-based oxidation, reductions were preferentially taken place at the bpy and metal (Ru^III/Ru^II) centers, respectively. Unlike 1 or [2]ClO₄ containing one free NH proton at the backface of H-Iz, [1']ClO₄ with two H-Iz units could selectively and effectively recognize F^-, OAc^-, and CN^- among the tested anions: F^-, OAc^-, CN^-, Cl^-, Br^-, I^-, SCN^-, HSO₄^-, and Η₂PΟ₄^- in CH₃CN via intermolecular NH···anion hydrogen bonding interaction. The difference in the sensing feature between [1']ClO₄ and 1/[2]ClO₄ could be rationalized by their pK_a values of 8.4 and 11.3/10.8, respectively.

Iridium(III) coordination of N(6) modified adenine derivatives with aminoacid chains

In this manuscript we report the preparation of three N⁶-aminoacid-adenine-derivatives: N-(7H-purin-6-yl)glycine·0.5H₂O (N⁶-GlyAde), N-(7H-purin-6-yl)-β-alanine·1.5H₂O (N⁶-β-AlaAde) and N-(7H-purin-6-yl)-γ-aminobutyric·2H₂O (N⁶-GabaAde) and the synthesis and X-ray characterization of three Ir(III) NAMI-A derivatives (NAMI-A is [imidazoleH][trans-Ru^IIICl₄(DMSO-κS)(imidazole)]) [trans-Ir^IIICl₄(DMSO-κS)(N³-H)-(7H-purin-6-yl)glycine-κN⁹] (1), [trans-Ir^IIICl₄(DMSO-κS)(N³-H)-(7H-purin-6-yl)-β-alanine-κN⁹] hydrate (2) and [trans-Ir^IIICl₄(DMSO-κS)(N³-H)-(7H-purin-6-yl)-γ-aminobutyryl-κN⁹] (3). In all complexes the metal center shows octahedral geometry with coordination to four chlorido ligands and one S coordinated dimethylsulfoxide (DMSO-κS). The coordination sphere of the metal is completed by the modified adenine molecule which is bound via N(9) and protonated at N(3). In two complexes the importance of lone pair (lp)-π interactions involving the adenine ring have been studied using density functional theory (DFT) calculations and the Bader's theory of atoms in molecules. Furthermore, the ability of complexes (1-3) to affect the cell viability was evaluated against three different cancer cell lines: human lung carcinoma cells (A549), human cervical carcinoma cells (HeLa) and human breast cancer cells (MCF7). We have also analyzed their ability to cleave the DNA experimentally and their affinity for two models of DNA has been studied using molecular docking simulations.

Synthesis, Characterisation and In Vitro Permeation, Dissolution and Cytotoxic Evaluation of Ruthenium(II)-Liganded Sulpiride and Amino Alcohol

Sulpiride (SPR) is a selective antagonist of central dopamine receptors but has limited clinical use due to its poor pharmacokinetics. The aim of this study was to investigate how metal ligation to SPR may improve its solubility, intestinal permeability and prolong its half-life. The synthesis and characterisation of ternary metal complexes [Ru(p -cymene)(L)(SPR)]PF6 (L1 = (R)-(+)-2-amino-3-phenyl-1-propanol, L2 = ethanolamine, L3 = (S)-(+)-2-amino-1-propanol, L4 = 3-amino-1-propanol, L5 = (S)-(+)-2-pyrrolidinemethanol) are described in this work. The stability constant of the [Ru(p -cymene)(SPR)] complex was determined using Job's method. The obtained value revealed higher stability of the metal complex in the physiological pH than in an acidic environment such as the stomach. The ternary metal complexes were characterised by elemental analysis, Fourier transform infrared spectroscopy (FT-IR), 1H and 13C nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), thermal analyses, Ultraviolet-Visible (UV-Vis). Solubility studies showed higher aqueous solubility for complexed SPR than the free drug. Dissolution profiles of SPR from the metal complexes exhibited slower dissolution rate of the drug. Permeation studies through the pig's intestine revealed enhanced membrane permeation of the complexed drug. In vitro methyl thiazolyl tetrazolium (MTT) assay showed no noticeable toxic effects of the ternary metal complexes on Caco-2 cell line.

Anthraquinone-bridged diruthenium(ii) complexes inhibit migration and invasion of human hepatocarcinoma MHCC97-H cells

Four diruthenium(ii) complexes exhibited anti-metastatic properties on MHCC97-H cells, which involved in the inhibition of migration and invasion, negative remodulation of the cytoskeleton, blocking cell cycles and regulation of relative signal pathways.

Anticancer Activities of Mononuclear Ruthenium(II) Coordination Complexes

Ruthenium compounds are highly regarded as potential drug candidates. The compounds offer the potential of reduced toxicity and can be tolerated in vivo. The various oxidation states, different mechanism of action, and the ligand substitution kinetics of ruthenium compounds give them advantages over platinum-based complexes, thereby making them suitable for use in biological applications. Several studies have focused attention on the interaction between active ruthenium complexes and their possible biological targets. In this paper, we review several ruthenium compounds which reportedly possess promising cytotoxic profiles: from the discovery of highly active compounds imidazolium [trans-tetrachloro(dmso)(imidazole)ruthenate(III)] (NAMI-A), indazolium [trans-tetrachlorobis(1H-indazole)ruthenate(III)](KP1019), and sodium trans-[tetrachloridobis(1H-indazole)ruthenate(III)] (NKP-1339) to the recent work based on both inorganic and organometallic ruthenium(II) compounds. Half-sandwich organometallic ruthenium complexes offer the opportunity of derivatization at the arene moiety, while the three remaining coordination sites on the metal centre can be functionalised with various coordination groups of various monoligands. It is clear from the review that these mononuclear ruthenium(II) compounds represent a strongly emerging field of research that will soon culminate into several ruthenium based antitumor agents.

Interaction of the NAMI-A complex with nitric oxide under physiological conditions

The NAMI-A ([ImH][RuCl₄(Im)(DMSO)], Im – imidazole, DMSO – dimethyl sulfoxide) interact with nitric oxide (NO) under physiological-like conditions, however it is rather kinetically sluggish NO scavenger.

Anticancer metallodrugs of glutamic acid sulphonamides: in silico, DNA binding, hemolysis and anticancer studies

In response to an increased demand for effective anticancer drugs, a series of disodium sulphonamides ofl-glutamic acid (L1–L3) was synthesized. Sulphonamides were complexed with copper(ii), nickel(ii) and ruthenium(iii) ions, separately and respectively.

Bioprocess development for nicotinic acid hydroxamate synthesis by acyltransferase activity of Bacillus smithii strain IITR6b2

In this work, acyltransferase activity of a new bacterial isolate Bacillus smithii strain IITR6b2 was utilized for the synthesis of nicotinic acid hydroxamate (NAH), a heterocyclic class of hydroxamic acid. NAH is an important pyridine derivative and has found its role as bioligand, urease inhibitor, antityrosinase, antioxidant, antimetastatic, and vasodilating agents. Amidase having acyltransferase activity with nicotinamide is suitable for nicotinic acid hydroxamate production. However, amidase can also simultaneously hydrolyze nicotinamide and nicotinic acid hydroxamate to nicotinic acid. Nicotinic acid is an undesirable by-product and thus any biocatalytic process involving amidase for nicotinic acid hydroxamate production needs to have high ratios of acyltransferase to amide hydrolase and acyltransferase to nicotinic acid hydroxamate hydrolase activity. Isolate Bacillus smithii strain IITR6b2 was found to have 28- and 12.3-fold higher acyltransferase to amide and hydroxamic acid hydrolase activities, respectively. This higher ratio resulted in a limited undesirable by-product, nicotinic acid (NA) synthesis. The optimal substrate/co-substrate ratio, pH, temperature, incubation time, and resting cells concentration were 200/250 mM, 7, 30 °C, 40 min, and 0.7 mgDCW ml−1, respectively, and 94.5 % molar conversion of nicotinamide to nicotinic acid hydroxamate was achieved under these reaction conditions. To avoid substrate inhibition effect, a fed-batch process based on the optimized parameters with two feedings of substrates (200/200 mM) at 40-min intervals was developed and a molar conversion yield of 89.4 % with the productivity of 52.9 g h−1 gDCW  −1 was achieved at laboratory scale. Finally, 6.4 g of powder containing 58.5 % (w/w) nicotinic acid hydroxamate was recovered after lyophilization and further purification resulted in 95 % pure product.

Pyridine analogues of the antimetastatic Ru(III) complex NAMI-A targeting non-covalent interactions with albumin

A series of pyridine-based derivatives of the antimetastatic Ru(III) complex imidazolium [trans-RuCl(4)(1H-imidazole)(DMSO-S)] (NAMI-A) have been synthesized along with their sodium-ion compensated analogues. These compounds have been characterized by X-ray crystallography, electron paramagnetic resonance (EPR), NMR, and electrochemistry, with the goal of probing their noncovalent interactions with human serum albumin (hsA). EPR studies show that the choice of imidazolium ligands and compensating ions does not strongly influence the rates of ligand exchange processes in aqueous buffer solutions. By contrast, the rate of formation and persistence of interactions of the complexes with hsA is found to be strongly dependent on the properties of the axial ligands. The stability of noncovalent binding is shown to correlate with the anticipated ability of the various pyridine ligands to interact with the hydrophobic binding domains of hsA. These interactions prevent the oligomerization of the complexes in solution and limit the rate of covalent binding to albumin amino acid side chains. Electrochemical studies demonstrate relatively high reduction potentials for these complexes, leading to the formation of Ru(II) species in aqueous solutions containing biological reducing agents, such as ascorbate. However, EPR measurements indicate that while noncovalent interactions with hsA do not prevent reduction, covalent binding produces persistent mononuclear Ru(III) species under these conditions.

Syntheses of ruthenium(II)-4,4′-biimidazole complexes and their potential anti-tumour activity

Synthesis and characterization of the RuII complexes, [Ru(N−N)3][CF3SO3]2, where N−N is 4,4′-biimidazole (complex 1a) or 2,2′-dimethyl-4,4′-biimidazole (1b), and the dimethylsulfoxide complexes RuCl2(DMSO)2(N−N) are reported. The air-stable, water-soluble complexes were characterized by elemental analysis, 1H NMR and IR spectroscopies, mass spectrometry, and solution conductivity. Evidence is presented also for the existence of the diruthenium complexes Ru2Cl4(DMSO)4(N−N), but there are insufficient data for elucidation of their structure. The complexes (and cisplatin) were tested against human breast-cancer cells (MDA-MB-435S) using an in vitro MTT assay, a colorimetric determination of cell viability: 1a and 1b exhibit the lowest IC50 values of 18 ± 5 and 36 ± 5 µmol/L, respectively, with cisplatin exhibiting an IC50 value of 35 ± 5 µmol/L. Isolation of DNA from cells treated with a solution of the Ru species showed no evidence of DNA-binding to the metal, although examination of the cells indicated that Ru was being taken up into the cells.

Synthesis and Characterization of Novel Ruthenium(III) Complexes with Histamine

Novel ruthenium(III) complexes with histamine [RuCl₄(dmso-S)(histamineH)] · H₂O (1a) and [RuCl₄(dmso-S)(histamineH)] (1b) have been prepared and characterized by X-ray structure analysis. Their crystal structures are similar and show a protonated amino group on the side chain of the ligand which is not very common for a simple heterocyclic derivative such as histamine. Biological assays to test the cytotoxicity of the compound 1b combined with electroporation were performed to determine its potential for future medical applications in cancer treatment.