Purification, structural characterization and immunostimulatory activity of polysaccharides from Umbilicaria esculenta.

In this study, an active component UP1-1 was isolated from Chinese Huangshan Umbilicaria esculenta via hot water extraction and purified by anion-exchange and gel-filtration chromatography. UP1-1 mainly composed of galactose, mannose and glucose in a molar ratio of 0.8:1.0:4.6 with an average molecular weight of 281 kDa. Methylation analysis of UP1-1 revealed the major glycosidic bonds comprised 1,6-linked Glcp, 1,4-linked Glcp, t-linked Glcp, 1,3,6-linked Manp, 1,3-linked Galp, t-linked Galp at the ratio of 2.28:0.38:0.32:0.63:0.25:0.29. Structural analysis results revealed that the backbone of UP1-1 consisted of →6)-β-D-Glcp-(1→, →6)-β-D-Manp-(1→, →4)-β-D-Glcp-(1 → residues with side chains of →3)-β-D-Galp-(1→, β-D-Galp-(1 → and β-D-Glcp-(1 → branches located at O-3 position of →6)-β-D-Manp-(1→. Immunostimulatory activity tests showed that UP1-1 could promote the phagocytic activity and NO production of RAW 264.7 cells in a dose-dependent manner. UP1-1 could significantly improve the proliferation effect of RAW 264.7 cells at the concentration of 50 μg/mL. Thus, UP1-1 exerted good immunostimulatory activity, suggesting that UP1-1 has a great potential application in pharmacological industry.