Enzymatic Saccharification of Polygonatum kingianum Coll. et Hemsl Polysaccharides: Structural Characterization and Immunological Activity
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Abstract:
The structural characteristics and immunomodulatory activity of Polygonatum kingianum Coll. et Hemsl polysaccharides were investigated under conditions of enzymatic saccharification. The results revealed that among the products of enzymatic saccharification in P. kingianum (SPKP), the contents of polysaccharides and reducing sugars accounted for 94.05% and 4.1%, respectively. Structural analysis of the polysaccharides using Fourier transform infrared spectroscopy revealed that these had furanose-specific absorption peaks at 1 016~1 147 and 931 cm-1, whereas the monosaccharide composition and molar ratios were arabinose: galactose: glucose: mannose: fructose (0.032: 0.117: 0.419: 0.048: 0.383), and the molecular weight (Mw) was 3 820 u. The main type of linkage was →4-Glcp-1→ (47.1%), and the corresponding branching degree was 34.1%. Combined with the results of the iodine–potassium iodide and Congo Red staining experiments, SPKP were inferred to be a three-stranded helical polysaccharides containing complex branches. The findings of RAW264.7 cell experiments indicated that P. kingianum polysaccharides are non-toxic within a wide range of concentrations and can promote cell proliferation, phagocytic capacity, and production of NO. Accordingly, it can be speculated that SPKP have good immunomodulatory activities, which are associated with polysaccharide structures. Our findings in this study may provide a reference for determining the structure-function relationships between polysaccharides and immunomodulatory activity, as well as the development of new methods for processing P. kingianum.
