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)-beta-D-Glcp-(1 ->, -> 6)-beta-D- Manp-(1 ->, -> 4)-beta-D-Glcp-(1 -> residues with side chains of -> 3)-beta-D-Galp-(1 ->, beta-D-Galp-(1 -> and beta-D-Glcp- (1 -> branches located at O-3 position of -> 6)-beta-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 mu g/mL. Thus, UP1-1 exerted good immunostimulatory activity, suggesting that UP1-1 has a great potential application in pharmacological industry. (c) 2021 Elsevier B.V. All rights reserved.