Structural characterization and immunoregulatory mechanism of a low-molecular-weight polysaccharide from lotus root

The extraction of polysaccharide from lotus root was highly homogenized, and the structure of the polysaccharide was not clear. Herein, we report a hot water method combined with alpha-amylase that was applied to extract lotus root polysaccharide. After purified, a lotus root polysaccharide fraction LP60-a with high purity and low molecule weight was obtained. Systematic characterization of the structure of LP60-a was achieved by monosaccharide composition, methylation and NMR analysis, showing that LP60-a was composed of alpha-1,6glucan linked with a small amount of arabinogalactan. Conformational determination showed that LP60-a was a three-helix polysaccharide with random coil conformation. Furtherly, the immunomodulatory activities of LP60a were investigated in RAW264.7 macrophages. The data indicated that LP60-a could enhance the proliferation and phagocytosis of macrophages significantly, and induce the expression of NO and TNF-alpha in macrophages without causing inflammation. Moreover, LP60-a promoted the phosphorylation of MAPK p38 and JNK, as well as NF-kappa B p65, indicating that LP60-a could activate RAW264.7 cells through MAPK and NF-kappa B signaling pathways. In conclusion, the results imply that LP60-a could enhance the immune function of macrophages, presenting a possibility to play a role as an immunomodulatory agent in dietary supplements.