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Structural characterization of a polysaccharide and a β-glucan isolated from the edible mushroom Flammulina velutipes

Smiderle, F.R., Carbonero, E.R., Mellinger, C.G., Sassaki, G.L., Gorin, P.A.J., Iacomini, M.
Phytochemistry 2006 v.67 no.19 pp. 2189-2196
glycosidic linkages, monosaccharides, methylation, glucans, Flammulina velutipes, carbohydrate composition, spectral analysis, mushrooms
Two polysaccharides were isolated from the basidiomycete Flammulina velutipes, via successive hot extraction with water, 2% and 25% aq. KOH, and then submitted to freeze-drying. The precipitate formed by repeated freeze-thawing from the 2% aq. KOH extraction PK2 was analyzed by determination of its monosaccharide composition, as well as by methylation analyses using GC-MS, mono- (13C, 1H NMR) and bidimensional (1H (obs.), 13C HMQC) spectroscopy, and controlled Smith degradations. It was established to be a branched β-glucan, with a main chain of (1 leads to 3)-linked-Glcp residues, substituted at O-6 by single-unit β-Glcp side chains. The precipitate formed by repeated freeze-thawing from the 25% KOH extraction PK25 contained Xyl, Man, and Glc and was heterogeneous by HSPEC and extraction with DMSO gave a soluble xylomannan (XM). It was homogeneous with a molar mass 30.8 x 10(4) g/mol (dn/dc = 0.186). Using the above chemical analyses, it was a xylomannan with Man and Xyl in a 3:2 molar ratio. Its main chain consisted of (1 leads to 3)-linked α-Manp units, mainly substituted at O-4 by β-Xylp units or with some β-Xylp-(1 leads to 3)-β-Xylp groups.