A new polysaccharide isolated from Morchella importuna fruiting bodies and its immunoregulatory mechanism.

A new polysaccharide (MIPW50-1) with a molecular weight of 28.5 kDa was isolated from Morchella importuna fruiting bodies. Structural analysis indicated that MIPW50-1 was composed of N-acetylglucosamine, galactose, glucose, and mannose with molar ratios of 1.00:14.95:1.53:10.51, and its structure was characterized as a repeating unit consisting of →2,3,6)-α-D-Manp-(1→, →3,6)-α-D-Manp-(1→, →2)-α-D-Galp-(1→, →6)-α-D-Manp-(1→, →4)-β-D-Glcp-(1→, →4)-α-D-GlcpNAc-(1→, →6)-α-D-Glcp-(1→, α-D-Galp-(1→, α-D-GlcpNAc-(1→ and β-D-Glcp-(1→. The immunoregulatory effect of MIPW50-1 was also evaluated. MIPW50-1 was capable of stimulating macrophage function, rising phagocytosis of RAW264.7 cells as well as promoting secretion of NO, TNF-α and IL-6. Moreover, the immunoblot and ELISA assays demonstrated that MIPW50-1 exerted immune-potentiating effect through the TLR4/JNK and Akt/NF-κB signalling pathways in RAW264.7 cells. This is the first polysaccharide containing N-acetylglucosamine isolated from Morchella mushrooms, and MIPW50-1 might be used as one of potential immunoenhancing components in functional foods.