Abstract
Umbilicaria esculenta has been used as a tonic food in China for several centuries owing to its pleasant flavor and health benefits. In this study, a water soluble polysaccharide, which we designated as UP2, with an average molecular weight of 3.33 × 105 Da, was isolated from U. esculenta cultivated in the Huangshan Mountain, by consecutive hot water extraction and anion-exchange chromatography. Gas chromatography analysis indicated that UP2 contained three kinds of monosaccharides, including mannose, glucose, and galactose at a molar ratio of 1.7:1.0:1.2. Linkage analysis of UP2 revealed the presence of (1 → 6)-linked glucosyl, (1 → 3,6)-linked glucosyl, t-linked galactosyl, (1 → 6)-linked galactosyl and (1 → 6)-linked mannosyl at a molar ratio of 0.7:4.6:4.1:2.2:9.1. Structural analysis determined that UP2 possessed a backbone consisting of (1 → 6)-linked β-D-glucopyranosyl and (1 → 6)-linked α-D-mannopyranosyl residues, which substituted at the O-3 position of (1 → 6)-linked β-D-glucopyranosyl residues by branches of (1 → 6)-linked α-D-galactopyranosyl and 1-linked β-D-galactopyranosyl residues. Immunostimulatory activity analysis showed that UP2 could stimulate the proliferation of RAW264.7 cells in a dose-dependent manner, and all the samples (20–500 μg/mL) were found to enhance nitric oxide production. The highest phagocytic activity of UP2 was observed at 200 μg/mL. Thus, UP2 may be a potential source of biological and pharmacological agents.
Highlights
Polysaccharides are found in animal cell membranes and cell walls of plants and microorganisms [1,2,3,4,5], and are compound of saccharide monomers linked through glycosidic bonds formed through their aldehyde and keto groups [6]
We have previously reported the extraction and preliminary characterization of polysaccharides from U. esculenta cultivated in the Huangshan Mountain, and demonstrated that the crude polysaccharides exhibited immunomodulatory activities in vitro [1, 25]
The water-soluble polysaccharide UP (5.68 g) was obtained from the thallus of U. esculenta cultivated in the Huangshan Mountain using the hot water extraction method
Summary
Polysaccharides are found in animal cell membranes and cell walls of plants and microorganisms [1,2,3,4,5], and are compound of saccharide monomers linked through glycosidic bonds formed through their aldehyde and keto groups [6]. They are essential biological macromolecules, and are directly involved in life processes, exhibiting a variety of important biological functions [2, 7]. Structure and Immunostimulation of a U. esculenta Polysaccharide support in the form of salaries for authors [QZ and JL], but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript
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