Structural characterization, chain conformation and immunomodulatory activity of a heteropolysaccharide from Inonotus hispidus

A new polysaccharide (IHP-1aa) was isolated from the fruiting body of Inonotus hispidus by hot water extraction, ethanol precipitation and column chromatography . The molecular weight of IHP-1aa was 26.9 kDa. Structural analysis showed that IHP-1aa consisted of glucose (Glc), galactose (Gal), fucose (Fuc), mannose (Man) and contained a certain amount of 3- O -methylgalactose (3- O -Me-Gal). The structure was mainly composed of →6)- α / β -D-Glc p -(1→, →6)- α -D-Gal p -(1→, →6)-(3- O -Me)- α -D-Gal p -(1→, →6)- α- D-Man p -(1 → and →2, 6)- α -D-Gal p -(1 → as the main chain. Branched at O-2 with single β -L-Fuc p -(1 → 6)- α -D-Gal p -(1 → 6)- α -D-Glc p -(1 → as major the side chain. The results of SEM, XRD and AFM combined with Congo red indicated that IHP-1aa may be amorphous granular chain conformation. In addition, IHP-1aa stimulated macrophage function and improved phagocytic ability of RAW264.7, as well as promoted the secretion of NO , TNF-α and IL-6. IHP-1aa, a 3- O -methylgalactose-containing heteropolysaccharide, was isolated for the first time from the I. hispidus , which may be used as a potential immunomodulator in functional foods.