Fractionation, chemical characterization and immunostimulatory activity of β-glucan and galactoglucan from Russula vinosa Lindblad.

Water-extracted polysaccharides from Russula vinosa Lindblad (WRP) were separated into three fractions (WRP-1, WRP-2 and WRP-3) by gradient ethanol precipitation and gel chromatography. Structural characterization indicated that WRP-1 was a branched β-(1→3)-glucan and exhibited rigid helical conformation in aqueous solution with Mw of 2,180 kDa and radius of gyration (Rg) of 123.4 nm. The galactoglucan of WRP-2 and WRP-3 were mainly composed of →6)-Galp-(1→ and →4)-Glcp-(1→ terminated by glucose and mannose, presenting much lower Mw (392 and 93.6 kDa) and Rg (57.6 and 42.6 nm), and more incompact flexible conformation than WRP-1. All fractions showed potential immunostimulatory activity by promoting macrophage proliferation, phagocytosis, as well as the release of nitric oxide and cytokines (TNF-α and IL-1β). WRP-1 with unique structure and conformation showed the best immunostimulatory effects among them. This study suggests that WRP could be explored as natural immunostimulator used in the food and pharmaceutical industry.