Structural properties and immunomodulatory activity of an α-glucan purified from the fruiting body of Stropharia rugosoannulata

A novel polysaccharide PSRa-2 was purified from Stropharia rugosoannulata fruiting bodies using high pressure homogenization-assisted dual enzyme method, ion exchange, and gel chromatography. The PSRa-2 was characterized via FT-IR, HPAEC, SEM, Congo red test, SEC-MALLS-RI, methylation analysis, and NMR analysis. Structural characterization revealed that PSRa-2 was an alpha-glucan with a Mw 455.6 kDa. The backbone of PSRa-2 was composed of -> 4)-alpha-D-Glcp-(1 -> and -> 3)-alpha-D-Glcp-(1 -> and branches of alpha-D-Glcp-(1 -> at position O-6 of -> 4,6)-alpha-D-Glcp-(1 ->. PSRa-2 induced splenocyte proliferation and protected splenocytes against 5-Fu-induced immunosuppression by restoring the proliferation and secretion of cytokines (TNF-alpha and IL-2) secretion levels. Thus, PSRa-2 exhibits obviously immunomodulatory activity and represents a potential natural immunomodulator.