Structural Characterization and Immunomodulatory Activity of a Novel Polysaccharide from Lepidium meyenii

A novel polysaccharide named as MC-1 was isolated from the roots of Lepidium meyenii using a water extraction method. Structural characterization revealed that MC-1 had an average molecular weight of 11.3 kDa and consisted of arabinose (26.21%), mannose (11.81%), glucose (53.66%), and galactose (8.32%). The main linkage types of MC-1 were proven to be (1 → 5)-α-L-Ara, (1 → 3)-α-L-Man, (1 → 2,6)-α-L-Man, (1 → )-α-D-Glc, (1 → 4)-α-D-Glc, (1 → 6)-α-D-Glc and (1 → 6)-β-D-Gal by methylation analysis, periodate oxidation-Smith degradation and NMR analysis. The immunostimulating assay indicated that MC-1 could significantly enhance the pinocytic and phagocytic capacity and promote the NO, TNF-α, and IL-6 secretion of RAW 264.7 cells, involving toll-like receptor 2, complement receptor 3, and mannose receptor mainly. These results suggested the potential utilization of MC-1 as an attractive functional food supplement candidate for hypoimmunity population.