Ana Lucia Ramalho Mercê

Effects of a lichen galactomannan and its vanadyl (IV) complex on peritoneal macrophages and leishmanicidal activity

A galactomannan (GMPOLY) isolated from lichen Ramalina celastri was complexed with vanadyl ion (IV;VO) forming the complex GMPOLY-VO. Both GMPOLY and GMPOLY-VO diminished the superoxide anion production by macrophages triggered with PMA, the complex giving rise to this effect at concentrations 100 times lower than GMPOLY. Macrophages treated with GMPOLY enhanced the nitric oxide production (40%), this effect not being observed when interferon-γ ((IFN-γ) or IFN-γ plus lipopolysaccharide (LPS) were present. No effect on nitric oxide production was observed by treatment of macrophage with GMPOLY-VO. Both GMPOLY and GMPOLY-VO exhibited leishmanicidal effects on the amastigote form of Leishmania amazonesis, but only GMPOLY-VO inhibited the growth of promastigote form.

Aqueous and solid complexes of iron(III) with hyaluronic acid. Potentiometric titrations and infrared spectroscopy studies.

The coordination of iron(III) ion to hyaluronic acid (Hyal) in aqueous solutions and solid state was accomplished by potentiometric titrations and infrared spectroscopy. The potentiometric titration studies provided the binding constants for the complexes found in the systems and the speciation of these species according to the variation of pH values. The complexes found presented a complexing ability through both the chelating moieties of Hyal (via the N-glucosamine and D-glucoronic acid), showing no special preference for either one while in solid state, but when in aqueous solution the complexation via the N-glucosamine moiety was the preferred, forming two complexed species, ML and ML(2) (log K(ML)=8.2 and log K(ML2)=7.9). The presence of a mu-oxo complex via the D-glucoronic acid was also detected in both aqueous (log K=6.7) and solid states via the N-glucosamine and D-glucoronic acid simultaneously linked to two Hyal chains. A structure for this latter complex was suggested. The results indicated that these complexes could be used in eliminating the excess iron(III) in living organisms.

Complexes of arabinogalactan of Pereskia aculeata and Co2+, Cu2+, Mn2+, and Ni2+.

The main interest in the biopolymer arabinogalactan is that it is edible. Complementing its high protein percentage, when complexed to essential metal ions, widens the use in food and pharmacology industries and technologies. The binding constants of Co2+, Cu2+, Mn2+ and Ni2+ with arabinogalactan, extracted from the leaves of Pereskia aculeata from Brazil were determined by potentiometric titrations and also the speciation according to pH values. The complexed species proposed by potentiometric titrations and the unique complexing ability of galacturonic acid groups towards Cu2+ and Ni2+ in the tridimensional web structure of arabinogalactan were confirmed by IR and EPR spectroscopies. The thermal stability of the complexed species also varied with the metal ion employed in the complexation when compared to the biopolymer alone. These complexes are new sources of additives for the food and pharmacology industries and carriers of essential metal ions to animal and vegetal biochemistry.

Fe(III) - Galactomannan Solid and Aqueous Complexes. Potentiometric, EPR Spectroscopy and Thermal Data

Galactomannans can be employed in food industries to modify the final rheological properties of the products. Since they are not absorbed by the living organisms they can also be used in dietary foods. The equilibria involving the interactions of Fe(III) and galactomannans and arabinogalactan of several leguminous plants were characterized by potentiometric titrations and EPR spectroscopy. The log of the equilibrium constants for the formation of ML species, where M is the metal ion and L is the monomeric unit of the biopolymers, were 15.4, 14.1 and 18.5, for the galactomannans of C. fastuosa, L. leucocephala and S. macranthera, respectively. Log K values for protonated species (MHL) were 3.1, 3.3, and were not detected for the galactomannan of S. macranthera. The log K values for the formation of ML2 were 14.1, 13.3 and 15.2, respectively. Early formation of insoluble products in the equilibrium with arabinogalactan and Fe(III) prevented acquisition of reliable data. The solid complexes assays showed a great dipolar interaction between two Fe(III) ions in the inner structure of the biopolymer which increased as the degree of substitution of the galactomannan decreased, and also showed the resulting thermal stability. The complexes impart a new possibility of providing essential metal ions in dietary foods since decomplexation of the complexes can occur at different pH values existing in the human body.

Two galactomannan preparations from seeds from Mimosa scabrella (bracatinga): Complexation with oxovanadium(IV/V) and cytotoxicity on HeLa cells

Two galactomannans, GALMAN-A and GALMAN-B, were isolated from seeds of Mimosa scabrella (bracatinga), with deactivation and exposure to native enzymes, respectively. They were treated with oxovanadium(IV) and oxovanadium(V), designated (VO(2+)/VO(3+)) to form GALMAN-A:VO(2+)/VO(3+) and GALMAN-B:VO(2+)/VO(3+) complexes, respectively. The potentiometric studies provided the binding constants for the complexes and the resulting complexed species were a function of pH. (51)V NMR spectra of GALMAN-A:VO(2+)/VO(3+) and GALMAN-B:VO(2+)/VO(3+) at pH 7.8 and at 30 degrees C indicated the occurrence of two types of complexes formed by oxovanadium ions and galactomannans. GALMAN-A:VO(2+)/VO(3+) and GALMAN-B:VO(2+)/VO(3+) caused loss of HeLa cells viability at concentrations of 50-200microg/mL. GALMAN-A:VO(2+)/VO(3+) exhibited low toxicity for 24h, although GALMAN-B:VO(2+)/VO(3+) was extremely toxic, since 50microg/mL was sufficient to decrease HeLa cell viability after 48h by 60%. GALMAN-A gave rise to a slight increase in cell proliferation after 48h at 100microg/mL, whereas GALMAN-B promoted a slight decrease at concentrations of 50-100microg/mL. GALMAN-A:VO(2+)/VO(3+) and GALMAN-B:VO(2+)/VO(3+) exhibited a significant decrease in cell proliferation after 48h, each reaching 60% inhibition at 5-10microg/mL. The complexes which caused this effect were at concentrations 10 times lower than the uncomplexed polymers.

Chemical equilibrium in the complexation of first transition series divalent cations Cu2+, Mn2+ and Zn2+ with chitosan

This study provided the data for calculating the stability constants formed in the aqueous HCl equilibrium of chitosan and Cu2+, Mn2+ and Zn2+, and determined the species distribution diagrams to show the influence of pH in the complexation systems based on data obtained from potentiometric and spectrophotometric titrations. The solid complexes further obtained from these aqueous HCl systems, were investigated by infrared spectroscopy. It was verified that chitosan coordinated with the cations Cu2+, Mn2+ and Zn2+ at pHs >4 >5 and >2 respectively, in ligand to metal ratio of 1:1. The logarithms of the binding constants for ML species presented the following stability order: Cu2+>Zn2+>Mn2+. Some possible complexed structures were suggested having both N and/or O atoms as binding sites with one or two monomers of the biopolymer studied.

Macrophage activation and leishmanicidal activity by galactomannan and its oxovanadium (IV/V) complex in vitro

Compounds that activate macrophage antimicrobial activity are potential targets for treatment of leishmaniasis. The present study investigated the in vitro immunomodulatory effects of a galactomannan (GALMAN-A) isolated from seeds of Mimosa scabrella and its oxovanadium (IV/V) complex (GALMAN-A:VO(2+)/VO(3+)) on macrophage activity. GALMAN-A increased nitric oxide levels by ~33% at a concentration of 250μg/ml, while GALMAN-A:VO(2+)/VO(3+) decreased nitric oxide levels by ~33% at a concentration of 50μg/ml. Furthermore, GALMAN-A increased interleukin-1 beta (IL-1β) and interleukin-6 (IL-6) levels by 5.5 and 2.3 times, respectively, at a concentration of 25μg/ml; at the same concentration, GALMAN-A:VO(2+)/VO(3+) promoted an increase in IL-1β and IL-6 production by 8 and 5.5 times, respectively. However, neither GALMAN-A nor GALMAN-A:VO(2+)/VO(3+) affected tumor necrosis factor alpha (TNF-α) or interleukin-10 (IL-10) levels. Importantly, both GALMAN-A and GALMAN-A:VO(2+)/VO(3+) exhibited leishmanicidal activity on amastigotes of Leishmania (L.) amazonensis, reaching ~60% activity at concentrations of 100 and 25μg/ml, respectively. These results indicate that GALMAN-A is three times more potent and its oxovanadium complex is twelve times more potent than Glucantime (300μg/ml), which is the drug of choice in leishmaniasis treatment. The IC50 value for GALMAN-A:VO(2+)/VO(3+) was 74.4μg/ml (0.58μg/ml of vanadium). Thus, the significant activation of macrophages and the noted leishmanicidal effect demonstrate the need for further studies to clarify the mechanisms of action of these compounds.

Equilibrium studies of galactomannan of Cassia fastuosa and Leucaena leucocephala and Cu2+ using potentiometry and EPR spectroscopy

Abstract The binding constants of Cu 2+ and galactomannans composed of sugar units of mannose and galactose from the seeds of Cassia fastuosa and Leucaena leucocephala were determined by potentiometric titrations and inspected by EPR spectroscopy. Two complexed species were found in both systems, one moiety being the metal ion (M) and the other moiety a sugar monomer of the polysaccharide (L), non-protonated, ML, and protonated, MHL. The values for the logarithms of the binding constants are in the range of 15 units for ML for both employed galactomannans, and 8.0 for MHL for Man:Gal medium average ratio 4:1 galactomannan ( C. fastuosa ) and 6.8 for Man:Gal medium average ratio 2.6:1 one ( L. leucocephala ). The EPR spectra have shown one octahedral complex species linked through the oxygen atoms of the hydroxyl groups of the monomer with tetragonal deformation. The A and g obtained values were A ∥ = 178G, g ∥ = 2.260, and g ⊥ = 2.050 and A ⊥ = 30G for CU 2+ with the galactomannans. This was assigned to be ML 2 complex which was only detected in the solid state due to the formation of insoluble products in solution, above pH value of 7.0. The extension of formation of complexed species of galactomannans with Cu 2+ is probably much more affected by the pH variation than by the degree of substitution of monomers of the chain of the biopolymers studied so far.

Evaluation of the complexes of galactomannan of Leucaena leucocephala and Co2+, Mn2+ , Ni2+ and Zn2+

The binding constants for the complexed species formed in aqueous solution between galactomannan of Leucaena leucocephala and the metal ions Co2+, Mn2+, Ni2+ and Zn2+ were determined by potentiometric titrations. The calculated values showed Ni2+ as the best Lewis acid towards the Lewis base -OH groups of the sugar monomers, with Zn2+ being the poorest. For all systems, a higher percentage of the complexed species was present near pH=7.0, although complexed species existed over a wide range of acidic and basic pH values. The isolated solid complexes were studied by TG-DSC thermal analysis and by EPR spectroscopy. The thermal profiles obtained showed higher thermal resistance to final degradation than the biopolymer alone for the complexed species ML having the smallest log K values. The EPR spectra confirmed the complexation of the metal ions via the Lewis base deprotonated hydroxyl groups (-O) and showed that the distances between metal ions in the complexed biopolymer structure depend on the nature of the metal ion. The ability of galactomannans to complex a variety of metal ions in their web like structure and the resistance to high temperatures and a wide range of pH values of these complexes open new perspectives in possible industrial uses whenever these properties are required, such as in bioremediation of waste waters and in the application of slow-release fertilizers.

Properties of complexes of galactomannan of Leucaena leucocephala and Al3+, Cu2+ and Pb2+.

The use of biopolymers in many industrial processes is on the increase. The different interactions of biopolymers and electrolytes either in aqueous solutions or in solid state provide different physico-chemical properties and a simple correlation cannot be established. In this study, in order to determine the properties of the complexes of galactomannan of Leucaena leucocephala (gal) with the metal ions Al3+ and Pb2+, toxic elements and Cu2+, essential, the logs of the binding constants of the complexes formed in the aqueous solutions were calculated. Their rheological properties, their thermal behavior, the infrared characteristics and shape and form of the films formed by those complexes in solid state were also determined. The aqueous solutions properties have shown a better complexation between gal and Al3+. The species distribution diagrams have shown an existence of complex species going from acidic to basic pH values. Infrared spectra have proved the complexations as well as the viscosity studies. Thermal stabilities in general were smaller in the complexed species than in the native biopolymers and the films obtained from aqueous solutions showed for Cu2+ the most different morphology compared to the biopolymer itself. A use can be suggested of this biopolymer in environmental remediations besides its already established industrial uses.