Isolation and characterization of glucans in Cantharellus cibarius

Mushrooms have been used as health supplements mostly in Asian countries, mainly for immunological, anti-inflammatory and antioxidant activities. Effects are primarily due to their β-glucan content. Most of the common mushrooms in the European diet are less studied, except for the white button mushroom, Agaricus bisporus. Therefore the aim of this project is to characterize glucans from other edible European mushrooms belonging to the phylum Basidiomycota using an optimized extraction procedure. Carbohydrate polymers were isolated with boiling water (PSVV), ammonium oxalate (2%, 80 °C) (PSAO) and NaOH (1 M, 100 °C) (PsNaOH). Compositional studies were conducted by methanolysis and GC, linkage analysis by GC-MS, NMR and enzymatic degradation by HPAEC PAD. Molecular size was determined with SEC-HPLC. Polymer yields were 1.9%, 0.4% and 2.5% for the aqueous, ammonium oxalate and alkali extracts, respectively. The SEC analysis showed two peaks in all fractions. PSVV (80kDa, 8kDa) was composed of 43% glucose which contained β(1-> 6) (16%), β(1-> 4) (10%) and 2% β(1-> 3) linkages. PSVV also contained 37% mannose with 31% of them being terminal units. PSAO (150kDa, 14kDa) was low in yield and contained 62% glucose monomers which were β(1-> 6) (17%) and β(1-> 4) (21%) linked. PSNaOH (120kDa, 15kDa) contained 83% glucose and 8% mannose. Linkage analysis showed presence of a β(1-> 3) linked backbone (32%) with branching in position 6 at every 4th unit in average. In addition, β(1-> 6) linked glucose units were detected (31%). The polysaccharides isolated from C.cibarius were shown to be mainly of β-glucan type, and our analysis shows that β(1-> 3,6) and β(1-> 6) glucans are more extensively extracted by alkali rather than by boiling water, while the aqueous extraction was more likely to extract β(1-> 6) and β(1-> 4) linkages. PSAO fraction resembled PSVV in composition.

Keywords: Mushrooms, beta-glucan, C. cibarius