17 research outputs found

    Comparative solution and structural studies of half-sandwich rhodium and ruthenium complexes bearing curcumin and acetylacetone

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    Half-sandwich organometallic complexes of curcumin are extensively investigated as anticancer compounds.Speciation studies were performed to explore the solution stability of curcumin complexes formed with [Rh(η5- C5Me5)(H2O)3]2+. Acetylacetone (Hacac), as the simplest β-diketone ligand bearing (O,O) donor set, was involved for comparison and its Ru(η6‑p‑cymene), Ru(η6‑toluene) complexes were also studied. 1H NMR, UV–visible and pH-potentiometric titrations revealed a clear trend of stability constants of the acac complexes: Ru(η6‑p‑cymene) > Ru(η6‑toluene) > Rh(η5-C5Me5). Despite this order, the highest extent of complex formation is seen for the Rh(η5-C5Me5) complexes at pH 7.4. Formation constant of [Rh(η5-C5Me5)(H2curcumin) (H2O)]+ reveals similar solution stability to that of the acac complex. Additionally, structures of two complexes were determined by X-ray crystallography. The in vitro cytotoxicity of curcumin was not improved by the complexation with these organometallic cations.Supplementary material: [http://cherry.chem.bg.ac.rs/handle/123456789/2875]This is the peer-reviewed version of the following article: Meszaros, J. P.; Poljarević, J.; Gal, T. G.; May, N. V.; Spengler, G.; Enyedy, E. A. Comparative Solution and Structural Studies of Half-Sandwich Rhodium and Ruthenium Complexes Bearing Curcumin and Acetylacetone. Journal of Inorganic Biochemistry 2019, 195, 91–100. [https://doi.org/10.1016/j.jinorgbio.2019.02.015

    Indolo[2,3- e ]benzazocines and indolo[2,3- f ]benzazonines and their copper( ii ) complexes as microtubule destabilizing agents †

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    A series of four indolo[2,3-e]benzazocines HL1–HL4 and two indolo[2,3-f]benzazonines HL5 and HL6, as well as their respective copper(ii) complexes 1–6, were synthesized and characterized by 1H and 13C NMR spectroscopy, ESI mass spectrometry, single crystal X-ray diffraction (SC-XRD) and combustion analysis (C, H, N). SC-XRD studies of precursors Vd, VIa·0.5MeOH, of ligands HL4 and HL6·DCM, and complexes 2·2DMF, 5·2DMF, 5′·iPrOH·MeOH provided insights into the energetically favored conformations of eight- and nine-membered heterocycles in the four-ring systems. In addition, proton dissociation constants (pKa) of HL1, HL2 and HL5, complexes 1, 2 and 5, overall stability constants (log β) of 1, 2 and 5 in 30% (v/v) DMSO/H2O at 298 K, as well as thermodynamic solubility of HL1–HL6 and 1–6 in aqueous solution at pH 7.4 were determined by UV–vis spectroscopy. All compounds were tested for antiproliferative activity against Colo320, Colo205 and MCF-7 cell lines and showed IC50 values in the low micromolar to sub-micromolar concentration range, while some of them (HL1, HL5 and HL6, 1, 2 and 6) showed remarkable selectivity towards malignant cell lines. Ethidium bromide displacement studies provided evidence that DNA is not the primary target for these drugs. Rather, inhibition of tubulin assembly is likely the underlying mechanism responsible for their antiproliferative activity. Tubulin disassembly experiments showed that HL1 and 1 are effective microtubule destabilizing agents binding to the colchicine site. This was also confirmed by molecular modelling investigations. To the best of our knowledge, complex 1 is the first reported transition metal complex to effectively bind to the tubulin-colchicine pocket

    Characterization of the binding sites of the anticancer ruthenium(III) complexes KP1019 and KP1339 on human serum albumin via competition studies

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    Indazolium trans-[tetrachloridobis(1H-indazole)ruthenate(III)] (KP1019) and its Na+ analogue (KP1339) are two of the most prominent non-platinum antitumor metal complexes currently undergoing clinical trials. After intravenous administration, they are known to bind to human serum albumin (HSA) in a noncovalent manner. To elucidate their HSA binding sites, displacement reactions with the established site markers warfarin and dansylglycine as well as bilirubin were monitored by spectrofluorimetry, ultrafiltration-UV-vis spectrophotometry, and/or capillary zone electrophoresis. Conditional stability constants for the binding of KP1019 and KP1339 to sites I and II of HSA were determined, indicating that both Ru(III) compounds bind to both sites with moderately strong affinity (log K (1)' = 5.3-5.8). No preference for either binding site was found, and similar results were obtained for both metal complexes, demonstrating low influence of the counter ion on the binding event

    Salicylamide and salicylglycine oxidovanadium complexes with insulin-mimetic properties.

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    Reaction of N-(2-hydroxybenzyl)-N-(2-picolyl) glycine (H(2)papy) with VOSO(4) in water gives the oxidovanadium(V) oxido-bridged dimer [{(papy)(VO)}(2) ÎĽ-O)] (1). Similarly, reaction of N-(2-hydroxybenzyl) glycine (H(2)glysal) with VOSO(4) gives [(glysal)VO(H(2)O)] (2) and reaction of salicylamide (Hsalam) with VOSO(4) in methanol gives [(salam)(2)VO] (3). The crystal structure of the oxido-bridged complex 1 is reported. The insulin-mimetic activity of all three complexes was evaluated with respect to their ability to phosphorylate protein kinase B (PKB). The speciations of complexes 1 and 2 were studied over the pH range 2-10. Complex 1 shows greater stability over the whole pH range but only 2 and 3 exhibit an insulin-mimetic effect

    Bis- and tris(pyridyl)amine-oxidovanadium complexes: characteristics and insulin-mimetic potential.

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    Two novel vanadium complexes, [V(IV)O(bp-O)(HSO4)] (1) and [V(IV)O(bp-OH)Cl2] x CH3OH (2 x CH3OH), where bp-OH is 2-{[bis(pyrid-2-yl)methyl]amine}methylphenol, were prepared and structurally characterised. EPR spectra of methanol solutions of 2 suggest exchange of Cl- for CH3OH and partial conversion to [VO(bp-OH)(CH3OH)3]2+. Speciation studies on the VO2+-bpOH system in a water/dmso mixture (4:1 v/v) revealed [VO(bp-O)(H2O)n]+ as the dominating species in the pH range 2-7. The insulin-mimetic properties of 1 and 2, [V(IV)O(SO4)tpa] (3), [V(IV)O(pic-trpMe)2] (5) and the new mixed-ligand complexes [V(V)O(pic-trpH)tpa]Cl2 (4Cl2) and [V(V)O(pic-OEt)tpa]Cl2 (6Cl2), tpa = tris(pyrid-2-yl)methylamine, picH-trpH = 2-carboxypyridine-5-(L-tryptophan)carboxamide (picH-trpMe is the respective tryptophanmethyl ester), pic-OEt = 5-carboethoxypyridine-2-carboxylic acid, were evaluated with rat adipocytes, employing two lipolysis assays (release of glycerol and free fatty acids (FFA)), respectively and a lipogenesis assay (incorporation of glucose into lipids). The IC50 values for the inhibition of lipolysis in the FFA assay vary between 0.41 (+/-0.03) (5) and 21.2 (+/-0.6) mM (2), as compared to 0.81 (+/-0.2) mM for VOSO4

    Comparative solution equilibrium and structural studies of half-sandwich ruthenium(II)(eta(6)-toluene) complexes of picolinate derivatives

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    Five Ru(II)(eta(6)-toluene) complexes formed with 2-picolinic acid and its various derivatives have been synthesized and characterized. X-ray structures of four complexes are also reported. Complex formation processes of [Ru(II) (eta(6)-toluene)(H2O)(3)](2+) organometallic cation with the metal-free ligands were studied in aqueous solution in the presence of chloride ions by the combined use of H-1 NMR spectroscopy, UV-visible spectrophotometry and pH-potentiometry. Solution stability, chloride ion affinity and lipophilicity of the complexes were characterized together with in vitro cytotoxic and antiproliferative activity in cancer cell lines being sensitive and resistant to classic chemotherapy and in normal cells as well. Formation of mono complexes such as [Ru(eta(6)-toluene)(L) (Z)](+/0) (L: completely deprotonated ligand; Z = H2O/Cl-) with high stability and [Ru(eta(6)-toluene)(L)(OH)] was found in solution. The plc values (8.3-8.7) reflect the formation of low amount of mixed hydroxido species at pH 7.4 at 0.2 M KCl ionic strength. The complexes are fairly hydrophilic and show moderate chloride ion affinity and fast chloride-water exchange processes. The studied complexes exhibit no cytotoxic activity in human cancer cells (IC50 gt 100 mu M), only complexes formed with 2-picolinic acid (1) and its 3-methyl derivative (2) represented a moderate antiproliferative effect (IC50 = 84.8 (1), 79.2 mu M (2)) on a multidrug resistant colon adenocarcinoma cell line revealing considerable multidrug resistant selectivity. Complexes 1 and 2 bind to human serum albumin covalently and relatively slowly with moderate strength at multiple binding sites without ligand cleavage.Supplementary material: [http://cherry.chem.bg.ac.rs/handle/123456789/3123
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