Strong differences in the in vitro cytotoxicity of three isomeric dichlorobis(2-phenylazopyridine)ruthenium(II) complexes

DNA interaction and cytotoxicity studies of new ruthenium(II) cyclopentadienyl derivative complexes containing heteroaromatic ligands

Four ruthenium(II) complexes with the formula [Ru(η(5)-C(5)H(5))(PP)L][CF(3)SO(3)], being (PP = two triphenylphosphine molecules), L = 1-benzylimidazole, ; (PP = two triphenylphosphine molecules), L = 2,2'bipyridine, ; (PP = two triphenylphosphine molecules), L = 4-Methylpyridine, ; (PP = 1,2-bis(diphenylphosphine)ethane), L = 4-Methylpyridine, , were prepared, in view to evaluate their potentialities as antitumor agents. The compounds were completely characterized by NMR spectroscopy and their crystal and molecular structures were determined by X-ray diffraction. Electrochemical studies were carried out giving for all the compounds quasi-reversible processes. The images obtained by atomic force microscopy (AFM) suggest interaction with pBR322 plasmid DNA. Measurements of the viscosity of solutions of free DNA and DNA incubated with different concentrations of the compounds confirmed this interaction. The cytotoxicity of compounds 1234 was much higher than that of cisplatin against human leukemia cancer cells (HL-60 cells). IC(50) values for all the compounds are in the range of submicromolar amounts. Apoptotic death percentage was also studied resulting similar than that of cisplatin.

Organometallic osmium arene complexes with potent cancer cell cytotoxicity

Iodido osmium(II) complexes [Os(η(6)-arene)(XY)I](+) (XY = p-hydroxy or p-dimethylaminophenylazopyridine, arene = p-cymene or biphenyl) are potently cytotoxic at nanomolar concentrations toward a panel of human cancer cell lines; e.g., IC(50) = 140 nM for [Os(η(6)-bip)(azpy-NMe(2))I](+) toward A2780 ovarian cancer cells. They exhibit low toxicity and negligible deleterious effects in a colon cancer xenograft model, giving rise to the possibility of a broad therapeutic window. The most active complexes are stable and inert toward aquation. Their cytotoxic activity appears to involve redox mechanisms.

Synthesis, single-crystal and solution structure analysis and in vitro cytotoxic activity of two novel complexes of ruthenium(II) with in situ formed flavanone-based ligands

Synthesis, structure and properties of two new flavanone complexes of Ru(ii) are described. The new complexes form during the reaction of ruthenium(iii) chloride with 3-aminoflavone (3-af) dissolved in an aliphatic alcohol. The formed products depend on the alcohol used and were found to be: cis-dichloridobis(3-imino-2-methoxyflavanone)ruthenium(ii)·3H(2)O (1) from a methanolic solution and cis-dichloridobis(3-imino-2-ethoxyflavanone)ruthenium(ii)·2H(2)O (2) from an ethanolic solution, in which the original ligand 3-af had been converted by dehydrogenative alcoholysis to an entirely new ligand. This paper presents the X-ray structure and detailed (1)H-NMR analysis of both new compounds, as well as the study of their antiproliferative activity. The coordination of Ru(ii) is octahedral with [RuCl(2)N(2)O(2)] chromophores, having trans chlorides and common Ru-L distances. Both 1 and 2 are highly cytotoxic towards the cisplatin resistant EJ and L1210 cell lines, and both complexes are as active as cisplatin in the sensitive cell lines. They display the ability to overcome cisplatin resistance in the drug resistant sub-lines EJcisR and L1210R. The present evidence suggests that the mechanism of biological activity may be different for these ruthenium compounds compared to cisplatin.

Arene ruthenium complexes as anticancer agents

Neutral or cationic arene ruthenium complexes providing both hydrophilic as well as hydrophobic properties due to the robustness of the ruthenium-arene unit hold a high potential for the development of metal-based anticancer drugs. Mononuclear arene ruthenium complexes containing P- or N-donor ligands or N,N-, N,O- or O,O-chelating ligands, dinuclear arene ruthenium systems with adjustable organic linkers, trinuclear arene ruthenium clusters containing an oxo cap, tetranuclear arene ruthenium porphyrin derivatives that are photoactive, as well as hexanuclear ruthenium cages that are either empty or filled with other molecules have been shown to be active against a variety of cancer cells.

A novel ruthenium(III) complex with a tridentate dianionic P,O,O-ligand showing high cytotoxic activity

Tris(o-anisyl)phosphane was reacted with ruthenium(III) chloride forming a novel Ru(III) complex of formula [Ru(PAn(3))(P(An)(phenolate)(2))Cl] containing a tridentate dianionic P,O,O-ligand and a bidentate neutral P,O ligand. The tridentate ligand was formed by elimination of two methyl groups from the starting ligand in the reaction with the ruthenium salt. The molecular structure was determined by single crystal X-ray diffraction analysis. The compound shows a high cytotoxic activity in ovarian cancer cell lines comparable with cisplatin and overcoming cisplatin-resistance.

Tuning heavy metal compounds for anti-tumor activity: is diversity the key to ruthenium’s success?

This review aims to bring the reader up to date with the more recent ruthenium compounds that have been synthesized and tested for their cytotoxicity. The chemistry of these transition metal complexes will be introduced and the basic principles that govern their common behavior outlined. The recent history of established compounds within this field will be presented alongside those that now represent the cutting-edge. The inherent variety within this class of compounds will lead the reader to appreciate their diversity and pose questions as to their similarities aside from the presence of a shared metal ion. This review aims to discuss and contextualize the state-of-the-art research within the context of the speculative advancement of this developing field. There is an evident need to specify the molecular and cellular targets of these drug molecules in order to ultimately elucidate their mode or modes of action. The evidence presented herein suggests that new avenues of research require novel analytical probes and methods for tracing the fate of ruthenium complexes in cells in order to understand their very promising cytotoxic activity.

Ruthenium polypyridyl complexes and their modes of interaction with DNA: is there a correlation between these interactions and the antitumor activity of the compounds?

Various interaction modes between a group of six ruthenium polypyridyl complexes and DNA have been studied using a number of spectroscopic techniques. Five mononuclear species were selected with formula [Ru(tpy)L₁L₂]⁽²⁻ⁿ⁾⁺, and one closely related dinuclear cation of formula [{Ru(apy)(tpy)}₂{μ-H₂N(CH₂)₆NH₂}]⁴⁺. The ligand tpy is 2,2′:6′,2″-terpyridine and the ligand L₁ is a bidentate ligand, namely, apy (2,2′-azobispyridine), 2-phenylazopyridine, or 2-phenylpyridinylmethylene amine. The ligand L₂ is a labile monodentate ligand, being Cl⁻, H₂O, or CH₃CN. All six species containing a labile L₂ were found to be able to coordinate to the DNA model base 9-ethylguanine by ¹H NMR and mass spectrometry. The dinuclear cationic species, which has no positions available for coordination to a DNA base, was studied for comparison purposes. The interactions between a selection of four representative complexes and calf-thymus DNA were studied by circular and linear dichroism. To explore a possible relation between DNA-binding ability and toxicity, all compounds were screened for anticancer activity in a variety of cancer cell lines, showing in some cases an activity which is comparable to that of cisplatin. Comparison of the details of the compound structures, their DNA binding, and their toxicity allows the exploration of structure–activity relationships that might be used to guide optimization of the activity of agents of this class of compounds.

The synthesis, chemical and biological properties of dichlorido(azpy)gold(III) chloride (azpy=2-(phenylazo)pyridine) and the gold-induced conversion of the azpy ligand to the chloride of the novel tricyclic pyrido[2,1-c][1,2,4]benzotriazin-11-ium cation

A new Au(III) coordination compound with the ligand 2-(phenylazo)pyridine has been synthesized and fully characterized by means of elemental analysis, IR, UV-visible, conductivity measurements, NMR, electrospray ionization (ESI-MS) and inductively coupled plasma optical emission spectrometry (ICP-OES). The chemical stability of the cation in this compound, [Au(azpy)Cl(2)](+) (abbreviated: Au-azpy), was analyzed by means of several physicochemical methods. While stable in the solid state, stability studies performed with the gold compound in solution showed an unexpected and unprecedented reactivity. A cationic organic derivative of 2-(phenylazo)pyridine, (abbreviated: pyrium), was produced from the solution and has been isolated as its chloride salt and characterized by crystal structure determination, elemental analysis, NMR, ESI-MS and conductivity studies in solution. This cyclization reaction is reported for the first time in the case of gold coordination compounds. The Au adduct and the pyrium cation were investigated as potential cytotoxic and anticancer agents, and both show moderate to high cytotoxic properties in cisplatin-sensitive and cisplatin-resistant ovarian carcinoma cell lines, A2780; and cisplatin-sensitive and cisplatin-resistant murine lymphocytic leukemia cell lines, L1210. Significant anticancer activity against the cisplatin resistant cell lines was found for the pyrium salt, ruling out the occurrence of cross resistance phenomena.

Interaction of 2-aminopyrimidine with dichloro-[I-alkyl-2-(naphthylazo) imidazole]palladium(II) complexes: kinetic and mechanistic studies

BACKGROUND

The anticancer properties of cisplatin and palladium(II) complexes stem from the ability of the cis-MCl2 fragment to bind to DNA bases. However, cisplatin also interacts with non-cancer cells, mainly through bonding molecules containing -SH groups, resulting in nephrotoxicity. This has aroused interest in the design of palladium(II) complexes of improved activity and lower toxicity. The reaction of DNA bases with palladium(II) complexes with chelating N,N'donors of the cis-MCl2 configuration constitutes a model system that may help explore the mechanism of cisplatin's anticancer activity. Heterocyclic compounds are found widely in nature and are essential to many biochemical processes. Amongst these naturally occurring compounds, the most thoroughly studied is that of pyrimidine. This was one of the factors that encouraged this study into the kinetics and mechanism of the interaction of 2-aminopyrimidine (2-NH2-Pym) with dichloro-[1-alkyl-2-(alpha-naphthylazo)imidazole]palladium(II) [Pd(alpha-NaiR)Cl2, 1] and dichloro-[1-alkyl-2-(beta-naphthylazo)imidazole]palladium(II) [Pd(beta-NaiR)Cl2, 2] complexes where the alkyl R = Me (a), Et (b), or Bz (c).

RESULTS

2-NH2-Pym reacts with 1a, 1b, and 1c to yield [[1-alkyl-2-(alpha-naphthylazo)imidazole]bis(2-aminopyrimidine)]palladium(II) (3a, 3b, 3c) dichloride and with 2a, 2b, and 2c to yield [[1-alkyl-2-(beta-naphthylazo)imidazole]bis(2-aminopyrimidine)]palladium(II) (4a, 4b, 4c) dichloride in an acetonitrile (MeCN) medium. The products were characterized using spectroscopic techniques (FT-IR, UV-Vis, NMR). The ligand substitution reactions follow second order kinetics - first order dependence on the concentration of the Pd(II) complex and 2-NH2-Pym. Addition of LiCl to the reaction does not influence its rate. The thermodynamic parameters (standard enthalpy of activation, Delta(double dagger)H degrees and standard entropy of activation, Delta(double dagger)S degrees) were determined from variable temperature kinetic studies. The magnitude of the second order rate constant, k2, at 298 K, was shown to increase thus: b

CONCLUSION

The kinetics of the reaction between Pd(II) complexes (1 and 2) and 2-NH2-Pym were examined spectrophotometrically at 530 nm in MeCN under pseudo-first-order conditions. The reaction rate is largely influenced by the pi-acidity of the chelating ligand, with substitution in the naphthyl azoimidazole backbone influencing the rate of the substitution process. The activation parameters, Delta(double dagger)H degrees and Delta(double dagger)S degrees, were determined and support the kinetic rate data.

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Affiliation(s)

Pradip Kumar Ghosh Department of Chemistry, Jadavpur University, Kolkata 700 032, India
Sushanta Saha Department of Chemistry, Jadavpur University, Kolkata 700 032, India
Ambikesh Mahapatra Department of Chemistry, Jadavpur University, Kolkata 700 032, India

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A theoretical study on the hydrolysis process of the antimetastatic ruthenium(III) complex NAMI-A

A hydrolysis process of the anticancer drug ImH[trans-Ru(III)Cl4(DMSO)(Im)] (nicknamed NAMI-A; Im=imidazole, DMSO=dimethyl sulfoxide) has been studied by using density functional theory (DFT) method, and the aqueous solution effect has been considered and calculated by conductor-like polarizable calculation model (CPCM). The stationary points on the potential energy surfaces for the first and second hydrolysis steps (including two different paths) were fully optimized and characterized. The following was found: for the first hydrolysis process, the computed relative free energies DeltaG degrees (aq) and rate constant (k) in aqueous solution are 23.2 kcal/mol and 6.11x10(-5) s(-1), respectively, in satisfactory agreement with the experimental values; for the second hydrolysis step, some disagreement still exists, and thus more accurate solvent model needs to be designed and improved. On the basis of our present limited work, it can reasonably suggest that the hydrolysis process of NAMI-A perform mainly via the first hydrolysis step and then the path 1 of the second hydrolysis step. The theoretical results provide the structural properties as well as the detailed energy profiles for the mechanism of hydrolysis of NAMI-A, such results may assist in understanding the reaction mechanism of the anticancer drug with the biomolecular target.

The hydrolysis process of the anticancer complex [ImH][trans-RuCl4(Im)2]: a theoretical study

A hydrolysis process of the anticancer drug [ImH][trans-RuCl4(Im)2] (ICR, Im=imidazole) has been investigated using density functional theory (DFT), and the aqueous solution effect has been considered and calculated by the conductor-like polarizable calculation model (CPCM). The stationary points on the potential energy surfaces for the first and second hydrolysis steps (including two different paths) were fully optimized and characterized. The results show that the computed values of free energy barriers DeltaG degrees (aq) and rate constants (k) in aqueous solution, in particular for the first hydrolysis step, are in excellent agreement with the experimental results. The analysis of electronic characteristics of species in the hydrolysis process suggests that the nucleophilic attack abilities (A) of hydrolysis products by biomolecular targets is in the sequence of A()<A()<A() (, and express the hydrolysis products of the first hydrolysis step, and of the second hydrolysis step through path 1 and path 2, respectively). On the basis of our present limited work, the following can reasonably be suggested: path 1 in the second hydrolysis step has thermodynamic preference over path 2, and thus the cis-diaqua species may dominate. The theoretical results provide the structural properties as well as the detailed energy profiles for the hydrolysis process of ICR, so such results may contribute to understanding the reaction mechanism of this drug with the biomolecular target.