Characterization of new oxovanadium(IV) complexes of saccharides

Antioxidant, anticancer activities and mechanistic studies of the flavone glycoside diosmin and its oxidovanadium(IV) complex. Interactions with bovine serum albumin

The natural antioxidant flavonoid diosmin, found in citric fruits, showed low antioxidant properties among other flavonoids due to its structural characteristics and low cytotoxicity against lung (A549) and breast (T47D, SKBR3 and MDAMB231) cancer cell lines. The anticancer behavior has been improved by the metal complex generated with the flavonoid and the oxidovanadium(IV) ion. This new complex, [VO(dios)(OH)3]Na5·6H2O (VOdios), has been synthesized and characterized both in solid and solution states. The interaction of the metal ion through the sugar moiety of diosmin precluded the improvement of the antioxidant effects. However, the cell-killing effects tested in human lung A549 and breast T47D, SKBR3 and MDAMB231 cancer cell lines, were enhanced by complexation. The anti-proliferative effects on the human lung cancer cell line were accompanied by cellular ROS generation and an increase in cytoplasm condensation. The breast cancer cell lines did not produce caspase3/7 activation, mitochondrial potential reduction and ROS generation. Therefore, a non-apoptotic form of cell death in a caspase- and oxidative stress-independent manner has been proposed. The protein binding ability has been monitored by the quenching of tryptophan emission in the presence of the compounds using bovine serum albumin (BSA) as a model protein. Both compounds could be distributed and transported in vivo and the complex displayed stronger binding affinity and higher contributions to the hydrogen bond and van der Waals forces.

Bovine serum albumin binding, antioxidant and anticancer properties of an oxidovanadium(IV) complex with luteolin

Chemotherapy using metal coordination compounds for cancer treatment is the work of the ongoing research. Continuing our research on the improvement of the anticancer activity of natural flavonoids by metal complexation, a coordination compound of the natural antioxidant flavone luteolin (lut) and the oxidovanadium(IV) cation has been synthesized and characterized. Using different physicochemical measurements some structural aspects of [VO(lut)(H2O)2]Na·3H2O (VOlut) were determined. The metal coordinated to two cis-deprotonated oxygen atoms (ArO(-)) of the ligand and two H2O molecules. Magnetic measurements in solid state indicated the presence of an effective exchange pathway between adjacent vanadium ions. VOlut improved the antioxidant capacity of luteolin only against hydroxyl radical. The antitumoral effects were evaluated on MDAMB231 breast cancer and A549 lung cancer cell lines. VOlut exhibited higher viability inhibition (IC50=17 μM) than the ligand on MDAMB231 cells but they have the same behavior on A549 cells (ca. IC50=60 μM). At least oxidative stress processes were active during cancer cell-killing. When metals chelated through the carbonyl group and one adjacent OH group of the flavonoid an effective improvement of the biological properties has been observed. In VOlut the different coordination may be the cause of the small improvement of some of the tested properties of the flavonoid. Luteolin and VOlut could be distributed and transported in vivo. Luteolin interacted in the microenvironment of the tryptophan group of the serum binding protein, BSA, by means of electrostatic forces and its complex bind the protein by H bonding and van der Waals interactions.

Using Raman spectroscopy in tablet moisture surface analysis: tablet surface markers

A method was developed to monitor the hydration of a tablet surface using chemical functional groups able to bind atmospheric water through H-bonding. In this study, generic oral dissolving loratadine tablets were used. These tablets have relatively high mannitol and lactose concentrations. Both mannitol and lactose have C-OH alcohol functional groups, several of which are potentially available for H-bonding with atmospheric water. The Raman intensity of the alcohol functional groups decreases upon hydration. This observation can be used to indirectly monitor water adsorbed to tablet surfaces at the alcohol sites. The hydration assay is based on the change in the Raman peak intensity of the alcohol C-OH stretching at 875.5 cm(-1). Consequently the decrease in the Raman intensity of this vibration can be used to monitor water adsorption. The Raman measurement of tablet surface water was compared to the direct moisture measurement method using a microbalance. The Raman spectroscopy is used to monitor the water that is specifically bound to the C-OH alcohol functional groups available for hydration. The microbalance was used to monitor the tablets' weight change during water adsorption and desorption. The distribution of the ratio of the Raman intensity of C-OH peak at 875.5 cm(-1) divided by the intensity of loratadine's C-Cl peak at 712.6 cm(-1) was experimentally determined to be a Gaussian distribution with a mean of 3.22+/-0.277. Raman analysis indicates that there is both tightly and loosely bound water at the tablet surface. This can be a useful technique with regard to inspecting and controlling the tablet drying process.

Vanadyl(IV) complexes with saccharides. Bioactivity in osteoblast-like cells in cultureThis paper is one of a selection of papers published in this Special issue, enititled Second Messengers and Phosphoproteins—12th International Conference

Complexes of vanadyl(IV) with 4 monosaccharides and 5 disaccharides were tested in 2 osteoblast-like cell lines (MC3T3E1 and UMR106). Many complexes caused stimulation of UMR106 proliferation (120% basal) in the range of 2.5 to 25 µmol/L. In the nontransformed osteoblasts, some vanadyl–saccharide complexes stimulated the mitogenesis (115% basal) in the same range of concentration. The glucose and sucrose complexes were the most efficient inhibitory agents (65% and 88% of inhibition vs. basal, respectively) for tumoral cells at 100 µmol/L. The galactose and turanose complexes exerted a similar effect in the nontransformed osteoblasts. On the other hand, all the complexes promoted the phosphorylation of the extracellular regulated kinases (ERKs). All together, these results indicate that the stimulation of ERKs is not the only factor that plays a role in the proliferative effects of vanadium derivatives since some compounds were inhibitory proliferating agents. Cell differentiation was evaluated by alkaline phosphatase specific activity and collagen synthesis in UMR106 cells. All the complexes inhibited alkaline phosphatase activity, with galactose complex as the most effective compound (IC50= 43 µmol/L). The complex with the trehalose TreVO was the most effective agent to stimulate collagen synthesis (142% basal) and glucose consumption (132% basal). A cytosolic tyrosine protein kinase and the kinase-3 of glycogen synthase seem to be involved in the stimulation of glucose consumption by vanadium derivatives. In this series, only TreVO gathered the characteristics of a good insulin mimetic and osteogenic drug. In addition, this complex was a good promoting agent of nontransformed osteoblast proliferation, whereas it inhibited tumoral osteoblasts. GluVO, the complex with glucose, was also more toxic for tumoral than for nontransformed cells. These 2 vanadium derivatives are good potential antitumoral drugs. All the results suggest that the biological effects of vanadium compounds are a complex phenomenon influenced by the complexation, the dose, and the nature of the ligands and the cells.

Synthesis, characterization, and biological activity of oxovanadium(IV) complexes with polyalcohols

Oxovanadium(IV) complexes of the polyalcohols sorbitol, galactitol, and mannitol, of stoichiometry Na(2)[VO(L)(2)].H(2)O, were obtained from aqueous alkaline solutions. They were characterized by elemental analysis, infrared and UV-vis spectroscopies, thermoanalytical (thermogravimetric and differential thermal analysis) data, and magnetic susceptibility measurements. The biological activities of the complexes on the proliferation, differentiation, and glucose consumption were tested on osteoblast-like cells (MC3T3E1 osteoblastic mouse calvaria-derived cells and UMR106 rat osteosarcoma-derived cells) in culture. The three complexes exerted a biphasic effect on cell proliferation, being slight stimulating agents at low concentrations and inhibitory in the range of 25-100 microM. All the complexes inhibited cell differentiation in tumor osteoblasts. Their effects on glucose consumption were also discussed. The free ligands did not show any effect on the studied biological parameters.

Synthesis, characterization and biological activity of oxovanadium (IV) complexes with cyclic polyalcohols

Oxovanadium (IV) complexes of the cyclic polyols conduritol C (cond) and myo-inositol (inos) of stoichiometry Na(2)[VO(cond)(2)].2H(2)O and Na(2)[VO(inos)(2)].H(2)O were obtained in aqueous alkaline solutions. They were characterized by infrared and UV-Vis spectroscopies, thermoanalytical (thermogravimetric and differential thermal analysis) data and magnetic susceptibility measurements. The biological activities of the complexes on the proliferation, differentiation and glucose consumption were tested on osteoblast-like cells in culture. Conduritol C and myo-inositol did not produce any effect on these parameters. Normal and tumoral cell proliferation was inhibited about (ca.40-60%) by the two oxovanadium (IV) complexes in concentrations as low as 100microM. The complexes were also inhibitory on cell differentiation (ca. 70-80%) while they stimulate glucose consumption. Comparisons of these effects with those of the oxovanadium (IV) cation, under the same experimental conditions, were also performed.

Investigations of different carbohydrate anomers in copper(II) complexes with d-glucose, d-fructose, and d-galactose by Raman and EPR spectroscopy

With the aim of verifying different carbohydrate anomers coordinated to copper(II) ions, some copper(II) complexes with D-glucose (Glc), D-fructose (Fru), and D-galactose (Gal) were prepared and investigated by spectroscopic techniques. Their compositions were verified by elemental, ICP-AES and thermal analyses, in addition to conductivity measurements. The compounds isolated were consistent with the formula Na2[Cu2(carbohydrate)3].8H2O and Na[Cu2(carbohydrate)3].6H2O for the aldoses Glc and Gal, respectively, and Na2[Cu3(carbohydrate)4].8H2O in the case of the ketose, Fru. EPR spectra of these solids showed a rhombic environment around the metal center and suggested the presence of different anomers of the carbohydrates in each case. By Raman spectroscopy, it was possible to verify the predominance of the beta anomer of d-glucose in the corresponding copper complex, while in the free ligand the alpha anomer is predominant. In the case of the analogous complex with d-galactose, the spectrum of the complex shows bands of both anomers (alpha and beta) in approximately the same relative intensities as those observed in the isolated free ligand spectrum. On the other hand, for the complex with d-fructose a mixture of both furanose (five-membered ring) and pyranose (six-membered ring) structures was detected with prevalence of the furanose structure. Based on variations in the relative intensities of characteristic Raman bands, the binding site for copper in the fructose ligand was identified as most likely the 1-CH2OH and the anomeric 1-OH, while in beta-D-glucose it is presumably the anomeric 1-OH and the O-5 atom. These results indicated that EPR and Raman spectroscopy are suitable supporting techniques for the characterization of carbohydrate anomers coordinated to paramagnetic ions.

Characterization of oxovanadium (IV) complexes of d-gluconic and d-saccharic acids and their bioactivity on osteoblast-like cells in culture

Oxovanadium (IV) complexes of the alpha-hydroxycarboxylic ligands D-gluconic and D-saccharic acids of stoichiometry Na(2)[VO(gluconate)(2)].H(2)O, K(2)[VO(saccharate)(2)].4H(2)O, Na(4)[VO(gluconate)(2)].2H(2)O and K(5)[VO(saccharate)(2)].4H(2)O were obtained in aqueous solutions; the first two in acid, the other two in alkaline media. They were characterized by infrared and UV-Vis spectroscopies, thermoanalytical (thermogravimetric and differential thermal analysis) data and magnetic susceptibility measurements. The complexes were found to be mononuclear, possessing the VO(2+) moiety, and the thorough analysis of the spectral data allowed the determination of the characteristics of the metal-to-ligand interactions. The biological activities of these complexes on the proliferation, differentiation and glucose consumption were tested on osteoblast-like cells in culture. Comparisons of these effects and those of the oxovanadium (IV) cation and the free ligands were performed. Different behaviors could be observed for the complexes obtained at acidic or alkaline pH-values, as well as for the different cellular types. The free ligands did not show any biological effect.

Synthesis of a new vanadyl(IV) complex with trehalose (TreVO): insulin-mimetic activities in osteoblast-like cells in culture

Vanadium compounds show interesting biological and pharmacological properties. Some of them display insulin-mimetic effects and others produce anti-tumor actions. The bioactivity of vanadium is present in inorganic species like the vanadyl(IV) cation or vanadate(V) anion. Nevertheless, the development of new vanadium derivatives with organic ligands which improve the beneficial actions and decrease the toxic effects is of great interest. On the other hand, the mechanisms involved in vanadium bioactivity are still poorly understood. A new vanadium complex of the vanadyl(IV) cation with the disaccharide trehalose (TreVO), Na(6)[VO(Tre)(2)].4H(2)O, here reported, shows interesting insulin-mimetic properties in two osteoblast cell lines, a normal one (MC3T3E1) and a tumoral one (UMR106). The complex affected the proliferation of both cell lines in a different manner. On tumoral cells, TreVO caused a weak stimulation of growth at 5 microM but it inhibited cell proliferation in a dose-response manner between 50 and 100 microM. TreVO significantly inhibited UMR106 differentiation (15-25% of basal) in the range 5-100 microM. On normal osteoblasts, TreVO behaved as a mitogen at 5-25 microM. Different inhibitors of the MAPK pathway blocked this effect. At higher concentrations (75-100 microM), the complex was a weak inhibitor of the MC3T3E1 proliferation. Besides, TreVO enhanced glucose consumption by a mechanism independent of the PI3-kinase activation. In both cell lines, TreVO stimulated the ERK phosphorylation in a dose- and time-dependent manner. Different inhibitors (PD98059, wortmannin, vitamins C and E) partially decreased this effect, which was totally inhibited by their combination. These results suggest that TreVO could be a potential candidate for therapeutic treatments.

Three new vanadyl(IV) complexes with non-steroidal anti-inflammatory drugs (Ibuprofen, Naproxen and Tolmetin). Bioactivity on osteoblast-like cells in culture

The synthesis and spectral and magnetic characterization of VO(2+) complexes with Ibuprofen (2-(4-isobutylphenyl)propionic acid), Naproxen (6-methoxy-alpha-methyl-2-naphthalene acetic acid) and Tolmetin (1-methyl-5-(4-methylbenzoyl)-1H-pyrrole-2-acetic acid) were studied. The complexes [VO(Ibu)(2)] x 5CH(3)OH, [VO(Nap)(2)] x 5CH(3)OH and [VO(Tol)(2)] were obtained from methanolic solutions under nitrogen atmosphere. The biological activities of these complexes on the proliferation of two osteoblast-like cells in culture (MC3T3E1 and UMR106) were compared with that of the vanadyl(IV) cation. The complexes exhibited different effects depending on the concentration and the cellular type, while no effect was observed for their parent drugs.