Research on Extraction, Structure Characterization and Immunostimulatory Activity of Cell Wall Polysaccharides from Sparassis latifolia

The cell wall polysaccharides were extracted from Sparassis latifolia fruit bodies by acid-alkali and superfine-grinding assisted methods, and the chemical characterization and in vitro immunity activities of these polysaccharide fractions were studied and compared. Results showed that superfine-grinding assisted extraction exhibited the highest yield of polysaccharides (SP, 20.80%) and low beta-glucan content (19.35%) compared with alkaline extracts. The results revealed that the 20% ethanol precipitated fraction (20E) from SP was mainly composed of beta-(1 -> 3)-glucan and alpha-(1 -> 4)-glucan. With the increase of ethanol precipitation, the fractions (30E, 40E, 50E) were identified as alpha-(1 -> 4)-glucan with different molecular weights and conformations. Cell wall polysaccharides extracted through NaOH (NSP) and KOH (KSP) extraction had similar yields with 8.90% and 8.83%, respectively. Structural analysis indicated that the purified fraction from KSP (KSP-30E) was a beta-(1 -> 3)-glucan backbone branched with beta-(1 -> 6)-Glcp, while the purified fraction from NSP (NSP-30E) mainly contained beta-(1 -> 3)-glucan with a small number of alpha-linked-Glcp. The two fractions both exhibited rigid chain conformation in aqueous solutions. All polysaccharide fractions exerted the activity of activating Dectin-1 receptor in vitro, and the KSP-30E mainly identified as beta-(1 -> 3)-glucan with the terminal group via 1 -> 6-linkage attached at every third residue exhibited a stronger enhancing effect than other fractions. Results suggested that KOH extraction could be efficient for the preparation of bioactive beta-(1 -> 3, 1 -> 6)-glucan as a food ingredient.