Spontaneous enanti-omorphism in poly-phased alkaline salts of tris-(oxalato)ferrate(III): crystal structure of cubic NaRb5[Fe(C2O4)3]2.

We show here that the phenomenon of spontaneous resolution of enanti-omers occurs during the crystallization of the sodium and rubidium double salts of the transition metal complex tris-(oxalato)ferrate(III), namely sodium penta-rubidium bis-[tris-(oxalato)ferrate(III)], NaRb5[Fe(C2O4)3]2. One enanti-omer of the salt crystallizes in the cubic space group P4332 with Z = 4 and a Flack absolute structure parameter x = -0.01 (1) and its chiral counterpart in the space group P4132 with x = -0.00 (1). All metal ions are at crystallographic special positions: the iron(III) ion is on a threefold axis, coordinated by three oxalate dianions in a propeller-like conformation. One of the two independent rubidium ions is on a twofold axis in an eightfold coordination with neighbouring oxalate oxygen atoms, and the other one on a threefold axis in a sixfold RbO6 coordination. The sodium ion is at a site of D3 point group symmetry in a trigonal-anti-prismatic NaO6 coordination.

Vanadium and cancer treatment: antitumoral mechanisms of three oxidovanadium(IV) complexes on a human osteosarcoma cell line.

We report herein the antitumor actions of three oxidovanadium(IV) complexes on MG-63 human osteosarcoma cell line. The three complexes: VO(oda), VO(oda)bipy and VO(oda)phen (oda=oxodiacetate), caused a concentration dependent inhibition of cell viability. The antiproliferative action of VO(oda)phen could be observed in the whole range of concentrations (at 2.5 µM), while VO(oda)bipy and VO(oda) showed a decrease of cell viability only at higher concentrations (at 50 and 75 µM, respectively) (p<0.01). Moreover, VO(oda)phen caused a decrease of lysosomal and mitochondrial activities at 2.5 µM, while VO(oda) and VO(oda)bipy affected neutral red uptake and mitochondrial metabolism at 50 µM (p<0.01). On the other hand, no DNA damage studied by the Comet assay could be observed in MG-63 cells treated with VO(oda) at 2.5-10 µM. Nevertheless, VO(oda)phen and VO(oda)bipy induced DNA damage at 2.5 and 10 µM, respectively (p<0.01). The generation of reactive oxygen species increased at 10 µM of VO(oda)phen and only at 100 µM of VO(oda) and VO(oda)bipy (p<0.01). Besides, VO(oda)phen and VO(oda)bipy triggered apoptosis as determined by externalization of the phosphatidylserine. The determination of DNA cleavage by agarose gel electrophoresis showed that the ability of VO(oda)(bipy) is similar to that of VO(oda), while VO(oda)(phen) showed the highest nuclease activity in this series. Overall, our results showed a good relationship between the bioactivity of the complexes and their structures since VO(oda)phen presented the most potent antitumor action in human osteosarcoma cells followed by VO(oda)bipy and then by VO(oda) according to the number of intercalating heterocyclic moieties.

Chelation therapies: a chemical and biochemical perspective.

Chelation therapy occupies a central place in modern medicine and pharmacology, because continuous studies with laboratory animals and extensive clinical experience demonstrate that acute or chronic intoxications with a variety of metals can be considerable improved by administration of a suitable chelating agent. In this review the chemical characteristics, properties and uses of the most common chelating agents as well as those of some new and very promising agents of this type, are discussed. In the second part of the review the biological and biochemical impact of these agents, as well as their use for the treatment of some selected diseases and disorders, are also analyzed and discussed in detail.

Spectroscopic behavior and biological activity of K3[VO(O2)2CO3]∙H2O.

The potassium salt of the carbonato oxodiperoxovanadate(V) complex, obtained by a known synthetic procedure, was thoroughly characterized by infrared, Raman, and electronic spectroscopy. The bioactivity of the complex on the cell proliferation was tested on osteoblast-like cells (MC3T3E1 osteoblastic mouse calvaria-derived cells and UMR106 rat osteosarcoma-derived cells) in culture. At low doses, the complex is more toxic for the nontransformed osteoblasts than for the tumoral ones, whereas at higher doses the deleterious effects are similar for both cell lines. This peroxo complex seems to be the most toxic compound that has so far been tested on osteoblast-like cells in culture.

Experimental and theoretical studies of calcium fructoborate.

Calcium fructoborate samples of composition Ca(C6H10O6BO)2 x 3 x 5H2O were characterized by chemical analysis, infrared and Raman spectroscopy, and thermoanalytical (thermogravimetric and differential thermal analysis) data. Theoretical studies, using density functional theory, were made for seven different structural models of the fructoborate moiety, and the most stable structure could be derived from these calculations. The results of the theoretical study also allow improving the assignment of the vibrational spectra of the compound.

Spectroscopic characterization of a VO2+ complex of oxodiacetic acid and its bioactivity on osteoblast-like cells in culture.

The oxovanadium(IV) complex of oxodiacetic acid (H2oda) of stoichiometry [VO(oda)(H2O)2], which presents an unprecedented tridentate OOO coordination, was thoroughly characterized by infrared, Raman, electronic, and electron paramagnetic resonance spectroscopies. The biological activity of the complex on the cell proliferation and differentiation was tested on osteoblast-like cells (MC3T3E1 osteoblastic mouse calvaria-derived cells and UMR106 rat osteosarcoma-derived cells) in culture. The complex caused inhibition of cellular proliferation in both osteoblast-like cells in culture, but the cytotoxicity was stronger in the normal (MC3T3E1) than in the tumoral (UMR106) osteoblasts. The effect of the complex in cell differentiation was tested through the specific activity of alkaline phosphatase of the UMR106 cells because they expressed a high activity of this enzyme. What occurs with other vanadium compounds [VO(oda)(H2O)2] is an inhibitory agent of osteoblast differentiation.

Copper complexes with heterocyclic sulfonamides: synthesis, spectroscopic characterization, microbiological and SOD-like activities: crystal structure of [Cu(sulfisoxazole)2(H2O)4] . 2H2O.

The synthesis, characterization and comparative biological study of a series of antibacterial copper complexes with heterocyclic sulfonamides were reported. Two kinds of complexes were obtained with the stoichiometries [Cu(L)2] . H2O and [Cu(L)2(H2O)4] . nH2O. They were characterized by infrared and electronic spectroscopies and the crystal structure of [Cu(sulfisoxazole)2(H2O)4] . 2H2O was determined by single crystal X-ray diffraction. It crystallized in the C2/c with Z = 8 monoclinic space group C2/c with Z = 8. The Cu(II) is in a slightly tetragonal distorted octahedron formed by four oxygen atoms from water molecules and two nitrogen atoms from two isoxazole rings. The antimicrobial activity was evaluated for all the synthesized complexes and ligands using the agar dilution test. The results showed that the complexes with five-membered heterocyclic rings were more active than the free sulfonamides while the pyrimidine, pyridine and pyridazine complexes had similar or less activity than the free ligands. In order to find an explanation for this behavior lipophilicity and superoxide dismutase-like activity were tested, showing that the [Cu(sulfamethoxazol)2(H2O)4] . 3H2O presented the highest antimicrobial potency and a superoxide dismutase-like activity comparable with pharmacological active compounds.

On the interaction of vanadium species with meso-2,3-dimercaptosuccinic acid.

The interaction of the VO2+ cation with meso-2,3-dimercaptosuccinic acid (DMSA) was investigated by electron absorption spectroscopy in aqueous solution at different pH values. The spectral behavior, complemented with a spectrophotometric titration, shows the generation of a [VO(DMSA)2]2- complex in which the oxocation interacts with two pairs of deprotonated -SH groups of the acid. It was also found that DMSA rapidly reduces VO3- to VO2+, which might be chelated by an excess of the acid. DMSA can also produce the partial reduction of a V2O5 suspension at pH=5.2. The results of this study suggest that DMSA might be a potentially useful detoxification agent for vanadium.

On the interaction of oxovanadium(IV) with homocysteine.

The interaction of the VO2+ cation with homocysteine was investigated by electron absorption spectroscopy in aqueous solution at different metal-to-ligand ratios. The direct reduction of vanadate(V) solutions with homocysteine was also investigated. The results suggest that the interaction is different from that found in the case of cysteine and occurs through pairs of amino and carboxylate groups of the amino acid. The interaction of VO2+ with homocystine, the oxidation product of homocysteine, was also analyzed. The interest of the results in relation to vanadium metabolism and detoxification is briefly discussed.

On the interaction of the vanadyl(IV) cation with lactose: inhibition effects of vanadyl(IV)/monosaccharide and disaccharide complexes upon alkaline phosphatase activity.

A new vanadyl(IV) complex of the disaccharide lactose was obtained in aqueous solution at pH = 13. The sodium salt of the complex, of composition Na4[VO(lactose)2].3H2O, has been characterized by elemental analysis and by ultraviolet-visible, diffuse reflectance, and infrared spectroscopies. Its magnetic susceptibility and thermal behavior were also investigated. The inhibitory effect on alkaline phosphatase activity was tested for this compound as well as for the vanadyl(IV) complexes with maltose, sucrose, glucose, fructose, and galactose. For comparative purposes, the free ligands and the vanadyl(IV) cation were also studied. The free sugars and the sucrose/VO complex exhibited the lowest inhibitory effect. Lactose-VO, maltose-VO, and the free VO2+ cation showed an intermediate inhibition potential, whereas the monosaccharide/VO complexes appeared as the most potent inhibitory agents.

Reduction of vanadium(V) with ascorbic acid and isolation of the generated oxovanadium(IV) species.

The interaction of sodium metavanadate and VOCl3 with ascorbic acid, one of the possible natural reducing agents of vanadium(V) to oxovanadium(IV), has been investigated. Three new VO2+ complexes could be isolated as microcrystalline powders. One of them, of composition K1.5Na0.5[VO(HAsc)(OH)3], contains ascorbic acid as a monodentate ligand. In the other two, K[VO(Diketo)(OH)] x H2O and Na3[VO(Diketo)2(OH)], the enolized form of 2,3-diketogulonic acid (one of the oxidation products of ascorbic acid), acts as a bidentate ligand. The complexes were characterized by means of electronic (absorption and reflectance) and infrared spectroscopy and magnetic susceptibility measurements. Their thermal behavior was investigated by thermogravimetric and differential thermal analyses. The interest of the investigated system in relation to vanadium detoxification is also discussed.

Spectroscopic and magnetic properties of a Ni(II) complex with citric acid.

The complex compound K2[Ni(cit)(H2O)2]2 x 4H2O (cit = triionized citrate ion) seems to be a good model for the investigation of Ni(II)/citrate interactions that are of interest in relation to nickel metabolism and bioaccumulation. Its infrared and Raman spectra were recorded and analyzed on the basis of its structural peculiarities. The magnetic susceptibility, investigated in the temperature range between 1.9 and 300 K, shows the absence of magnetic interactions between the two metal centers present in this structure.

Metal complexes of carnosine.

The ligand properties of carnosine are analyzed. The stoichiometry, stability constants, and structural and spectroscopic characteristics of its coordination compounds with transition and representative metal cations are discussed. Mixed ligand systems containing carnosine are also presented. The biological activity of some of these metallic complexes is briefly considered.

Oxovanadium(IV) and oxovanadium(V) complexes relevant to biological systems.

Different aspects of the coordination chemistry of oxovanadium(IV) and oxovanadium(V), relevant to the bioinorganic chemistry of vanadium, are presented. Some of the investigated complexes are good models for different aspects of the metabolism and detoxification of vanadium or for a better characterization and understanding of the structural and electronic peculiarities of the coordination spheres of VO2+ and VO2+ in biomolecules. Their structural, spectroscopic and magnetic properties are briefly discussed. The investigated systems include ligands such as reduced and oxidized glutathione, L-ascorbic acid, nucleotides and related systems, carbohydrates, phosphates, carboxylic acids, oxine derivatives and some others.

Vibrational and 57Fe-Mössbauer spectra of FeTbGe2O7.

The infrared, Raman and 57Fe-Mössbauer spectra of FeTbGe2O7 were recorded and analyzed on the basis of its crystallographic data. For comparative purposes, similar measurements were also performed with FeYGe2O7 and with other isostructural compounds containing different lanthanide cations.

Characterization of bis(isoorotato)diaquamagnesium(II) dihydrate: a potentially useful complex for magnesium supplementation.

The synthesis and crystal structure of a new Mg(II) complex of stoichiometry [Mg(isoor)2(H2O)2].2H2O, where isoor is the monoanion of 5-carboxyuracil (isoorotic acid), are reported. The structure, solved by single-crystal X-ray diffractometry, shows that it crystallizes in the triclinic space group P(-1) with Z = 1. The electronic, IR and Raman spectra of the complex are briefly discussed. Its thermal behavior was also investigated by means of thermal gravimetry (TG) and differential thermal analysis (DTA) measurements in an oxygen atmosphere. Dissolution studies support the usefulness of the compound for magnesium supplementation.

Na2Zn3(CO3)4.3H2O: a potentially useful compound for zinc supplementation.

The infrared and Raman spectra of the title compound were recorded and are briefly discussed on the basis of its structural characteristics. Its thermal behaviour was investigated by means of TG and DTA measurements. Several dissolution tests were also performed. The results support the potential usefulness of this double carbonate as a useful compound for Zn(II) supplementation.

On the interaction of the VO2+ cation with cystine.

The interaction between the VO2+ cation and cystine was investigated by electron absorption spectroscopy in aqueous solutions at different metal-to-ligand ratios. Reduction of NaVO3 solutions with cysteine gave similar spectra. The results suggest that interaction occurs through the carboxylate and amino groups of the ligand. The interest of the results in relation to vanadium metabolism are commented upon.

Interaction of the vanadyl (IV) cation with carnosine and related ligands.

The interaction of the vanadyl (IV) (VO2+) cation with carnosine (the dipeptide beta-alanyl-histidine) has been investigated by electron absorption spectroscopy at high ligand-to-metal ratios and at different pH values. The results show that in the range 6.0-8.5, the cation interacts with the imidazole group of four different carnosine molecules and points to the presence of an axially coordinated water molecule. These suppositions were confirmed by the behavior of the VO2+/imidazole system, which was investigated under similar experimental conditions, and supported by previous ENDOR (electron-nuclear double resonance) results. The study was complemented with additional measurements using the glycylglycine, glycylglycine/imidazole, and histidine systems as ligands.

A spectrophotometric study of the interaction of VO2+ with cytosine in nucleotides.

The interaction of VO2+ with cytidine-monophosphate, -diphosphate, and -triphosphate has been investigated at different pH values and metal-to-ligand ratios by differential UV-absorption spectroscopy. It is shown that at pH values between 3 and 5 and for metal-to-ligand ratios up to 0.5, the cytosine ring is involved in coordination. On the other hand, measurements performed at pH = 7 show the absence of this type of interaction. Some comments on the possible structural characteristics of the generated complexes are made on the basis of the known coordination behavior of cytosine. Similar spectroscopic measurements with the systems VO2+/PO(3-)4, VO2+/P2O(4-)7, and VO2+/D-ribose were also performed in order to complement the analysis of the experimental results.