Structural characterization, immune activity, and action mechanisms of fractionated polysaccharides from Athyrium multidentatum (Doll.) Ching

A water-soluble polysaccharide (AFP) was extracted from Athyrium Multidentatum (Doll.) Ching by water extraction and alcohol precipitation method and purified by column chromatography. AFP was characterized by Fourier transform infrared (FT–IR) spectroscopy, ultraviolet-visible (UV–Vis) spectroscopy, circular dichroism (CD) spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), Congo red (CR) binding assay, monosaccharide composition and molecular weight analyses. 1D and 2D nuclear magnetic resonance (NMR) studies revealed two structural components in AFP, which are →4-β-D-Manp-(1→4)-β-D-Xylp-(1→4)-β-D-Xylp-(1→2)-β-D-Galp-(1→ and β-D-Glcp-(1→4)-β-D-Glcp-(1→4)-β-D-Glcp-(1→2)-β-D-Galp-(1→. AFP exhibited significant immunological activities in both normal and immunosuppressed mice. Dectin-2/SYK/MAPK/non-classical NF-κB signaling pathways might play a crucial role in the immunomodulatory actions of AFP. Current results provided an important basis for the development of AFP as a natural immunoregulator.