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Montevideo, Uruguay

Becco L.,Laboratorio Of Interacciones Moleculares | Rodriguez A.,University of Barcelona | Bravo M.E.,National Autonomous University of Mexico | Prieto M.J.,University of Barcelona | And 4 more authors.
Journal of Inorganic Biochemistry | Year: 2012

The mixed-chelate copper(II) complexes Casiopeínas® have been tested in several models in vitro and in vivo, showing promising antitumoral results. However, their mechanism of action remains to be defined. Trying to get a deeper insight into their molecular mode of action, further analyses, including gel electrophoresis, atomic force microscopy and circular dichroism were carried out to study their interaction with DNA and some cytoskeleton proteins. Our results revealed that the interaction of Casiopeínas triggers DNA cleavage by a free radical mechanism. The tested complexes showed a differential response to reducing and scavenger agents. Differences on target preference were also evident using double stranded oligonucleotides as sequence competitors. Surprisingly, distamycin A, a minor groove binder, enhanced the Casiopeínas' action on DNA. On the other hand, the tested Casiopeínas produce strong changes in protein structure of tubulin, integrin and fibronectin. All together these results suggest a multiple mode of action for these metal-based drugs. In addition, since it has been proposed that antitumor drugs efficiently interacting with DNA could also show activity against Trypanosoma cruzi, etiologic agent of Chagas disease, we evaluated the activity of these compounds on this protozoan parasite. The tested complexes showed in vitro anti-T. cruzi activity similar to the anti-trypanosomal reference drug Nifurtimox. © 2012 Elsevier Inc. All rights reserved.

Gancheff J.S.,Catedra de Quimica Inorganica | Hahn F.E.,University of Munster
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2012

The reaction of K2ReCl6 with 1,2-bis(2,3- dimercaptobenzamido)ethane (H4-1), and 1,2-bis(2,3- dimercaptobenzamido)benzene (H4-2) in the presence of Na 2CO3 in methanol affords dinuclear complexes of Re V. Experimental evidence supports the presence of self-assembled complexes with two {Re(S2C6H3)3} units connected in a triple-stranded fashion. Density Functional Theory (DFT) studies on geometry and electronic properties were conducted employing the hybrid B3LYP and PBE1PBE functionals. The helical (ΔΔ and ΛΛ) and meso-helical (ΔΛ) isomers were considered. For the helicate complexes included in this study, differences in the stability of the isomers were observed originating in different steric and strain interactions between the three ligand strands. The geometries at the minimum exhibit a distorted trigonal-prismatic coordination environment at the metal centers. Natural bond orbitals (NBO) analysis indicates the presence of Re-S bonds which are strongly polarized toward the non-metal. Time-Dependent DFT (TD-DFT) calculations were performed for a further understanding of the optical spectra. The calculations show the occupied 5d orbitals of the rhenium lying beneath occupied sulfur-based MOs. The general features of the electronic spectra in the visible region are reasonably reproduced by the calculations. The analysis of molecular orbitals also allows the assignment of the origin for all experimentally detected absorption bands. In the high-energy region of the spectrum the absorptions are attributed to ligand-to-metal-ligand charge transfer (LMLCT), in which sulfur-based orbitals and unoccupied orbitals at the rhenium atom and the benzene-o-dithiolato groups are involved. Also in the blue region, shoulders originating from LMLCT are observed. © 2012 Elsevier B.V. All rights reserved.

Gancheff J.S.,Catedra de Quimica Inorganica
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2011

The electronic spectra of triple-stranded complexes of Ti(IV) with bis(benzene-o-dithiolato) ligands (H4-L1 = 1,2-bis(2,3-dimercaptobenzamido)ethane; H4-L2 = 1,2-bis(2,3-dimercaptobenzamido)benzene) were investigated at the TD-DFT level of theory employing B3LYP/LANL2DZ. The influence of the nature (aliphatic or aromatic) of the spacer bridging both {Ti(S2C6H 3)3} units on the absorptive features of the dinuclear complexes was also studied. B3LYP/LANL2DZ leads to spectra accounting for four absorption bands. At the lowest-energy region, the most important transitions are due to ligand-to-metal charge transfer (LMCT), in which out-of-plane ligand-centered orbitals and titanium-based MOs are involved. In going to the blue-region, a third band was detected with excitations showing an important contribution from ligand-to-ligand charge transfer (LLCT) and indeed, a combined LMCT + LLCT character has been considered. This observation seems to arise from a decrease in the metallic character of the LUMO-derivatives involved in the excitations. The origin of the absorption band at the highest-energy part of the spectrum is assigned to a LLCT. The influence of the nature of the spacer on the molar absorption coefficients (ε) for this band has been clearly observed. The complex bearing aliphatic spacer shows ε of about 5 E+4 M-1 cm-1, while the one containing an aromatic spacer present a value of ε of about 2 E+5 M-1 cm-1. © 2010 Elsevier B.V. All rights reserved.

Benitez J.,Catedra de Quimica Inorganica | Becco L.,Laboratorio Of Interacciones Moleculares | Correia I.,University of Lisbon | Leal S.M.,Industrial University of Santander | And 8 more authors.
Journal of Inorganic Biochemistry | Year: 2011

In the search for new therapeutic tools against diseases produced by kinetoplastid parasites five vanadyl complexes, [VIVO(L-2H)(phen)], including 1,10-phenanthroline (phen) and tridentate salicylaldehyde semicarbazone derivatives as ligands have been synthesized and characterized in the solid state and in solution by using different techniques. EPR suggested a distorted octahedral geometry with the tridentate semicarbazone occupying three equatorial positions and phen coordinated in an equatorial/axial mode. The compounds were evaluated in vitro on epimastigotes of Trypanosoma cruzi, causative agent of Chagas disease, Leishmania panamensis and Leishmania chagasi and on tumor cells. The complexes showed higher in vitro anti-trypanosomal activities than the reference drug Nifurtimox (IC50 values in the range 1.6-3.8 μM) and increased activities in respect to the free semicarbazone ligands. In vitro activity on promastigote and amastigote forms of Leishmania showed interesting results. The compounds [VO(L1-2H)(phen)] and [VO(L3-2H)(phen)], where L1 = 2-hydroxybenzaldehyde semicarbazone and L3 = 2-hydroxy-3-methoxybenzaldehyde semicarbazone, resulted active (IC50 2.74 and 2.75 μM, respectively, on promastigotes of L. panamensis; IC 50 19.52 and 20.75 μM, respectively, on intracellular amastigotes of L. panamensis) and showed low toxicity on THP-1 mammalian cells (IC 50 188.55 and 88.13 μM, respectively). In addition, the complexes showed cytotoxicity on human promyelocytic leukemia HL-60 cells with IC 50 values of the same order of magnitude as cisplatin. The interaction of the complexes with DNA was demonstrated by different techniques, suggesting that this biomolecule could be a potential target either in the parasites or in tumor cells. © 2010 Elsevier Inc.

Fernandez M.,Catedra de Quimica Inorganica | Varela J.,University of the Republic of Uruguay | Correia I.,University of Lisbon | Birriel E.,University of the Republic of Uruguay | And 6 more authors.
Dalton Transactions | Year: 2013

Searching for prospective metal-based drugs for the treatment of Chagas disease, a new series of ten mixed-ligand oxidovanadium(iv) complexes, [V IVO(L-2H)(NN)], where L is a tridentate salicylaldehyde semicarbazone derivative (L1-L5) and NN is either 5-amine-1,10-phenanthroline (aminophen) or 5,6-epoxy-5,6-dihydro-1,10-phenanthroline (epoxyphen), were synthesized. The compounds were characterized in the solid state and in solution. EPR spectroscopy suggests that the NN ligands act as bidentate through both nitrogen donor atoms in an axial-equatorial mode. The stability of the complexes in solution was investigated by EPR and 51V-nuclear magnetic resonance spectroscopies. The complexes were evaluated in vitro for their activities against Trypanosoma cruzi (T. cruzi), the parasite responsible for the disease, and their selectivity was analyzed using J-774 murine macrophages, as a mammalian model. All the complexes are more active than both the reference drug Nifurtimox and the previously reported [VIVO(L-2H)(NN)] complexes. In general they are more active than the corresponding free NN ligands. Complexation led to highly increased selectivities towards the parasite. In addition, the lipophilicity of the compounds was determined and correlated with the observed activity in order to perform a QSAR (quantitative structure-activity relationship) study. A clear quadratic correlation is found. This study also confirms the influence of the structure of the co-ligand on the anti-T. cruzi effect. To get insight into the mechanism of action of the compounds, the changes in biochemical pathways promoted by two of the most active and most selective complexes are studied by analyzing a few of the parasite excreted metabolites by 1H NMR spectroscopy. The combined information suggests that the mitochondrion could be a target for these complexes. Furthermore, DNA was preliminarily evaluated as a potential target by using atomic force microscopy (AFM), which showed that the complexes display an ability to interact with this biomolecule. This journal is © The Royal Society of Chemistry.

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