Simple and effective purification approach to dissociate mixed water-insoluble α- and ß-D-glucans and its application on the medicinal mushroom Fomitopsis betulina.

Differences in anomericity and in the branching degree of glucans lead to characteristic intermolecular association that influences their solubility in water or other solvents. A simple purification approach, based on the glucan solubility in aq. 0.1 M NaOH solution, was applied for the separation of mixed water-insoluble α-D-glucans from ß-D-glucans extracted from fruiting bodies of Fomitopsis betulina, which is an underexploited medicinal mushroom. The results indicated that the ß-D-glucan is constituted by (1→3)-linked ß-D-Glcp units substituted at O-6 by non-reducing ß-D-Glcp and (1→6)-linked ß-D-Glcp units, while the α-D-glucan has a linear (1→3)-linked glucan structure. Thus, the 0.1 M NaOH treatment proved to be a simple, efficient and low-cost purification method for separation of water-insoluble glucans with different anomeric configurations and degree of branching that were interacting by intermolecular forces.

Chemical characterization and wound healing property of a ß-D-glucan from edible mushroom Piptoporus betulinus.

A water-soluble ß-D-glucan was obtained from fruiting bodies of Piptoporus betulinus, by hot aqueous extraction followed by freeze-thawing procedure and dialysis. Its molar mass distribution and conformational behavior in solution was assessed by size-exclusion chromatography coupled with multiangle laser light scattering, showing a polysaccharide with an average molecular weight of 2.5 × 105 Da with a random coil conformation for molecular weights below 1 × 106 Da. Typical signals of ß-(1 → 3)-linkages were observed in NMR spectrum (δ 102.7/4.76; 102.8/4.74; 102.9/4.52; and δ 85.1/3.78; 85.0/3.77) and also signals of O-6 substitution at δ 69.2/4.22 and 69.2/3.87. The analysis of partially O-methylated alditol acetates corroborates the NMR results, indicating the presence of a ß-D-glucan with a main chain (1 → 3)-linked, substituted at O-6 by single-units of glucose. The ß-D-glucan showed no toxicity on human colon carcinoma cell line (Caco-2) up to 1000 µg mL-1 and promoted cell migration on in vitro scratch assay, demonstrating a potential wound healing capacity.

Structural characterization and rheological properties of a gel-like ß-d-glucan from Pholiota nameko.

A crude fraction (SCW) was extracted with cold water from Pholiota nameko and showed mannose (24.1%), galactose (44.9%) and glucose (31%). Purification procedures resulted in a polysaccharide fraction (bG-PN), that showed only glucose. NMR and methylation analyses of bG-PN indicated a ß-d-glucan-(1→3)-linked, substituted at O-6 by ß-d-Glcp or (1→6)-linked ß-d-Glcp side chains. Rheological studies of crude and purified fractions at the same concentration showed similar shear-thinning behavior and gel-like structure which indicates no need to isolate the polymer to achieve some desirable rheological properties. SCW (at 1% and 2%) and bG-PN (at 2%) presented thermal stability during heating and cooling, suggesting that the physical structure of gels (SCW and bG-PN at 2%) and viscoelastic fluid (SCW at 1%) formed were not altered in the tested temperature range. Our results suggest that P. nameko ß-d-glucans can be applied in different food preparations as thickener or gelling agents modifying their rheological properties.

Evaluation of microwave-assisted and pressurized liquid extractions to obtain ß-d-glucans from mushrooms.

Microwave-assisted extraction (MAE) and pressurized liquid extraction (PLE) were compared as advanced technologies to obtain polysaccharides (particularly biologically active ß-glucans) from Pleurotus ostreatus and Ganoderma lucidum fruiting bodies. Extraction effectiveness was compared by a full-factorial experimental design (response surface methodology, RSM), using water as extraction solvent. Total carbohydrate content of the obtained extracts and polysaccharide yields were the variable responses investigated, while temperature and extraction time were the experimental factors. Temperature showed stronger influence in the polysaccharide extraction than time. The latter factor slightly affected MAE but not PLE extractions. Optimal conditions within the studied range were determined for each extraction method and species based on the desirability functions. Regarding the polysaccharide composition, the main differences between the species were more quantitative rather than qualitative, since NMR analyses indicated that all extracts contained mainly ß- and α-glucans and heteropolysaccharides. Both extraction systems were effective for polysaccharide extraction from mushrooms.