Supramolecular hydrogels of ß-cyclodextrin linked to calcium homopoly-l-guluronate for release of coumarins with trypanocidal activity.

Association constants and thermodynamicsparameters on inclusion of four 3-amido coumarins that present trypanocidal activity, into 6-amino-ß-cyclodextrin (1:1 stoichimetry) were determined. In addition, pure homopolymeric-α-l-guluronate fraction prepared by partial hydrolysis of sodium alginate from Sub-Antarctic Kelp Durvillaea antarctica was conjugated with 6-amino-ß-cyclodextrin (64% yield). To glycoconjugates, 3-amido coumarins were incorporated (73% of encapsulation) and supramolecular hydrogels were prepared by gelation with Ca2+ ions. The trypanocidal activity of the inclusion complexes increased by 10%. Likewise, an increase in diffusion in artificial membrane was observed (13%). It was found that the inclusion complexes increased the variation of the mitochondrial potential of T. cruzi (17%). The lowest release of substituted amidocoumarins (ACS) from supramolecular hydrogels occurred at pH 1.2 whereas the maximum release (34%) was observed at pH 8.0. Encapsulation of lipophilic bioactive compounds in supramolecular hydrogels allows the generation of release systems sensitive to pH with potential application in biomedicine.

Chemical structure and biological properties of sulfated fucan from the sequential extraction of subAntarctic Lessonia sp (Phaeophyceae).

This work is related to the structural characterization of the sulfated polysaccharide from Lessonia sp and the study of its antioxidant and antiparasitic properties. Sequential extraction afforded D-mannitol as the only low MW sugar alcohol. Extraction with 2% CaCl2 afforded in 3.0% yield, a sulfated fucan (SF). Its major fraction (48.5% yield), isolated by ion-exchange chromatography corresponds to a linear polymer of α-l-fucopyranosil residues linked 1→3, sulfated at the O-4 and partially at O-2 positions. By alkaline extraction, sodium alginate (10.3% yield) was obtained. The antioxidant capacity of SF by ESR showed high elimination index (IC50, mg/mL) of hydroxyl (0.27), alkoxy (10.05), and peroxyl (82.88) radicals in relation to commercial mannitol. SF showed activity against the epimastigote form of Trypanosoma cruzi parasite (250 µg/mL) and low cytotoxicity in murine cells (367 µg/mL). The elimination capacity of radicals in aqueous medium of SF would allow its potential biomedical application.

Characterization of bacteria using its O-antigen with surface-enhanced Raman scattering.

The O-antigen determines the specificity of bacterial serotype, a sort of bacterial fingerprinting. In this work we report the extraction, purification and characterization of the O-antigen of two pathogenic bacteria, Escherichia coli O16 and Salmonella typhimurium. Molecular fingerprints found in the vibrational spectra represent a powerful analytical technique for identification (or differentiation) of molecular moieties in complex systems such as pathogens. In addition, advantages of vibrational Raman scattering are unique thanks to the high sensitivity and specificity achieved via surface-enhanced Raman scattering (SERS). SERS is used here to take advantage of characteristic vibrational frequency differences of O-antigens, thus allowing bacterial differentiation. Characteristic fundamental vibrational modes associated with the monosaccharide N-acetylglucosamine and deformations of the O-antigen chains provide the main spectroscopic differences between the O-antigens of E. coli O16 and S.typhimurium.

Characterization of a neutral polysaccharide with antioxidant capacity from red wine.

A neutral fraction (PS-SI) (0.3g/L) with MW of 74kDa, which contained galactose, arabinose, mannose, and glucose in the molar ratio of 1.0:0.6:0.4:0.2 was obtained by treatment of the whole polysaccharide extracted from red wine with cetrimide, followed by gel permeation chromatography. Spectroscopic and methylation analyses indicated that PS-SI is a mixture of neutral polysaccharides, consisting mainly of beta (1-->3)-linked galactopyranosyl residues, with side chains of galactopyranosyl residues at positions O-6. Arabinofuranosyl residues linked alpha (1-->5), alpha-mannopyranosyl and glucosyl residues appear to be components of different polysaccharides. The in vitro antioxidant capacity of fractions of wine polysaccharide was studied by hydroxyl radical scavenging and ORAC assays. Fraction PS-SI presented the strongest effect on hydroxyl radicals (IC(50)=0.21).

Characterization of a fucoidan from Lessonia vadosa (Phaeophyta) and its anticoagulant and elicitor properties.

Blades of Lessonia vadosa (Phaeophyta) were extracted with 2% CaCl(2) solution, affording in 4.4% yield a polysaccharide which contained fucose and sulfate groups in the molar ratio 1.0:1.12. The high negative optical activity value ([alpha](D)(22)=-134.0 degrees ), FT-IR and NMR analysis suggest the presence of a fucoidan. (13)C NMR spectrum of the polysaccharide obtained by solvolytic desulfation of native fucoidan indicated the major presence of 1-->3 linked alpha-l-fucan. Depolymerization of the native fucoidan with H(2)O(2) in the presence of copper(II) acetate gave in 54.8% yield a fraction with 33.7% of sulfate content. The native fucoidan (MW 320,000) showed good anticoagulant activity whereas the radical depolymerized fraction (MW 32,000) presented a weak anticoagulant activity. These polysaccharides showed significant activation of phenylalanine-ammonia lyase (PAL), lipooxygenase (LOX) and glutathione-S-transferase (GST) defence enzyme activities in tobacco plants.

Carrageenans from chilean samples of Stenogramme interrupta (Phyllophoraceae): structural analysis and biological activity.

Carrageenans extracted from cystocarpic and tetrasporic Stenogramme interrupta were analysed by chemical and spectroscopic methods. The carrageenan from cystocarpic plants is composed predominantly of 0.5 M KCl-insoluble and 1 M KCl-soluble fractions. The insoluble fraction contained iota-carrageenan as the major component with alpha-carrageenan and pyruvated carrageenan as minor components. The soluble fraction is highly heterogeneous and did not contain the precursors mu- and nu-carrageenans. The polysaccharide from tetrasporic plants is composed of zeta- and lambda-carrageenans, and low sulfated galactans. It is soluble in KCl and partly cyclized by alkaline treatment. The antiviral and anticoagulant properties of the insoluble polysaccharide fraction from cystocarpic S. interrupta and the polysaccharide from tetrasporic S. interrupta are reported the results of which suggest promising antiherpetic activity.

Heterogeneity of carrageenans from Chondrus crispus.

Carrageenans extracted from gametophytic and sporophytic Chondrus crispus were analysed by hydrolysis, KCl fractionation and 1H NMR spectroscopy. The carrageenan from gametophytic plants is composed predominantly of two KCl insoluble fractions which contain kappa-carrageenan as the major component with 1-carrageenan and sulphated galactans as minor components. The precursor mu- and v-carrageenans were not found in the soluble fraction. The extract from sporophytic plants is composed mainly of a KCl soluble fraction which could be separated into 10 fractions by ion-exchange chromatography. The major component did not show a lambda-type structure but one of a xi-carrageenan.