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

Abstract

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 β-glucan content (19.35%) compared with alkaline extracts. The results revealed that the 20% ethanol precipitated fraction (20E) from SP was mainly composed of β-(1→3)-glucan and α-(1→4)-glucan. With the increase of ethanol precipitation, the fractions (30E, 40E, 50E) were identified as α-(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 β-(1→3)-glucan backbone branched with β-(1→6)-Glcp, while the purified fraction from NSP (NSP-30E) mainly contained β-(1→3)-glucan with a small number of α-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 β-(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 β-(1→3, 1→6)-glucan as a food ingredient.