RESUMO

A water-soluble sulfated heterorhamnan (Gb1) was isolated from the green seaweed Gayralia brasiliensis and purified by ultrafiltration, yielding a homogeneous polysaccharide (Gb1r). Both fractions contained rhamnose, xylose, galacturonic and glucuronic acids, galactose, and glucose. Chemical and spectroscopic methods allowed the determination of Gb1 and Gb1r chemical structure. Their backbones were constituted by 3-, 2-, and 2,3-linked rhamnosyl units (1:0.49:0.13 and 1:0.58:0.17, respectively), which are unsulfated (13.5 and 14.6%), disulfated (16.6 and 17.8%) or monosulfated at C-2 (8 and 8.6%) and C-4 (24.5 and 23.4%). Gb1 was oversulfated giving rise to Gb1-OS, which presented ~2.5-fold higher content of disulfated rhamnosyl units than Gb1, as determined by methylation analyses and NMR spectroscopy. Gb1 and Gb1-OS potently reduced the viability of U87MG human glioblastoma cells. Gb1 caused cell cycle arrest in the G1 phase, increased annexin V-stained cells, and no DNA fragmentation, while Gb1-OS increased the percentage of cells in the S and G2 phases and the levels of fragmented DNA and cells double-stained with annexin V/propidium iodide, suggesting an apoptosis mechanism. The results suggest that the different effects of Gb1 and Gb1-OS were related to differences in the sulfate content and position of these groups along the polysaccharide chains.

Assuntos

RESUMO

In this paper, the biologically inert agarose was selectively modified at C6 of ß-d-Galp units to produce an amino derivative with antibacterial property. The synthetic route involved the preparation of tosyl and azido agarose intermediates. All the polysaccharide derivatives were characterized by mono- and bidimensional 1H and 13C NMR and FT-IR analysis. A water-soluble amino polymer (Mw = 39,000 g mol-1, DSamino = 0.50) was produced by partial acid hydrolysis showing bactericidal and bacteriostatic activity against P. aeruginosa (ATCC 9027), S. aureus (ATCC 6538), and E. coli (ATCC 25922), with MIC values lower than 2.5 mg mL-1 and MBC values ranging from 2.5 to 5.0 mg mL-1.

Assuntos

RESUMO

In this study we described the synthesis of a hybrid polysaccharide harboring moieties of ulvan and kappa-carrabiose. Alkylamines (1,3-diaminopropane and 1,6-diaminohexane) were selectively inserted into ß-D-GlcAp and α-L-IdoAp units in the ulvan structure via an amide bond formation producing ulvan-amide derivatives F-DAP (N% = 1.77; Mw = 208 kg mol-1) and F-DAH (N% = 1.77; Mw = 202 kg mol-1), which were reacted with kappa-carrabiose via reductive amination to produce hybrid ulvan-kappa-carrabiose polysaccharides F-DAP-Kb (N% = 1.56; Mw = 206 kg mol-1) and F-DAH-Kb (N% = 1.16; Mw = 200 kg mol-1). All the ulvan derivatives were characterized by 1H and 13C NMR spectroscopy and did not show cytotoxicity against human dermal fibroblasts (HDFa) at the concentrations of 25, 100, and 500 µg mL-1, neither anticoagulant properties at the range of 10-150 µg mL-1. Therefore, the ulvan-amide derivatives and the hybrid ulvan-kappa-carrabiose polysaccharides showed good biocompatibility in vitro, presenting as worthy candidates for tailoring scaffolds for biomedical applications.

Assuntos

RESUMO

The interaction between galactomannans, guar gum (GG) with sodium lauryl ether sulphate (SLES) was demonstrated using conductometric, tensiometric, pyrene probe and 1H NMR analyses. SLES and GG formed aggregates and reduced the surface tension at a critical aggregation concentration. The interaction was attributed to the presence of surfactant ethoxyl (EO) groups, since in conductometric, tensiometry and pyrene probe analyses using the non-ethoxylated form, sodium lauryl sulphate - SLS, no aggregation was observed. The aggregates formed between SLES and GG presented a negative zeta potential indicating that the polymer is surrounded by SLES and according to the dynamic light scattering analysis (DLS), presented a size of approximately 26 nm. The determination of the thermodynamic parameters showed that the aggregation occurs spontaneously and is a driven-enthalpy and entropy process. SLES and GG interaction could be explored to produce formulations with lower concentrations of surfactants, using commonly used thickeners as GG.

Assuntos

RESUMO

Different hydrolysis conditions to produce κ-carrageenan oligosaccharide alditols were studied and the depolymerization process monitored by capillary electrophoresis (CE). Semisynthesis, ion-exchange and exclusion chromatography were used to obtain and isolate sulfated di-, tetra- and hexasaccharide alditols, the last being fully characterized for the first time. Those derivatives were used as standards to validate a new quantitative CE analytical method which was used to compare two different partial hydrolysis methodologies: an acid hydrolysis followed by reduction and a one-pot reductive hydrolysis using 4-methylmorpholine borane. The resulting depolymerization profiles were quite different from each other. Optimal hydrolysis conditions to produce high yields of specific sulfated oligosaccharides as well as particular mixtures of oligosaccharide alditols were determined. Moreover, using the novel CE method, we were able to distinguish up to eight different oligosaccharides in the hydrolysate mixtures.