A b-glucan from the Fruit Bodies of Edible Mushrooms Pleurotus eryngii and Pleurotus ostreatoroseus
Carbonero, E. R.a; Gracher, A. H. P. a; Smiderle, F. R. a; Rosado, F. R. b; Sassaki, G. L. a; Gorin, P. A. J. a; Iacomini, M. a
a Departamento de Bioquímica e Biologia Molecular, UFPR, Caixa Postal 19046, CEP 81531-990, Curitiba, PR, Brasil; b Centro Universitário de Maringá (CESUMAR), Av. Guedner, n. 1610, Maringá, PR, Brasil.
e-mail:ecarbonero@bol.com.br
Mushrooms are known for their nutritional and medicinal value and the diversity of their bioactive components. The glucans of basidiomycetes are an important class of polysaccharides with potential biological activities. P. eryngii and P. ostreatoroseus were extracted with CHCl3-MeOH and then MeOH-H2O. Each resulting residue was submitted to hot water extractions, and the extracted polysaccharides were recovered by EtOH precipitation (EPW-PE and EPW-PO for P. eryngii and P. ostreatoroseus, respectively). For purification, EPW-PE and EPW-PO were submitted to freeze-thawing procedures. The insoluble fractions (IEPW-PE and IEPW-PO) show glucose as main monosaccharide components. In order to elucidation of the linkage type of glucans, IEPW-PE and IEPW-PO were submitted to methylation analysis, showing the presence of a branched (1®3), (1®6)-linked b-glucan. 13C NMR and 1H (obs.),13C HMQC spectra, had signals corresponding to all carbons from the polysaccharide: C-1/H-1 at d 103.1/4.21 corresponding to non-reducing ends units, while those at d 102.9/4.51 are from 3-O-substituted and 3,6-di-O-substituted units. The b-configuration was shown by C-1 signals at low field and H-1 signals at high field. The signals at d 86.6 and 86.3 arose from substitutions at O-3, while those at d 86.0 and 76.6 are from similar substitutions and free O-3 from non-reducing end units of b-Glcp. Non-substituted and O-substituted -CH2 signals are at d 61.2; 61.0; 60.9 and 68.4, respectively. The C-6 signals were confirmed from the inverted signal of the DEPT spectrum. The structure of the main chain was identified by a controlled Smith degradation. It proved to be a linear (1®3)-linked b-glucan with six typical signals at d 102.9; 86.1; 76.3; 72.8; 68.4 and 60.9, arising from C-1, C-3, C-5, C-2, C-4 and C-6, respectively. Thus, according to the all data for cold water-insoluble fractions was a branched b-glucan, with a main chain of (1®3)-linked-Glcp residues, substituted at O-6 by single-unit b-Glcp side chains, on average to every third residue of the backbone, as in scleroglucan.
Supported by Capes and PRONEX-Fundação Araucária.
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