Structural characterisation and immunomodulatory activity of polysaccharides from white asparagus skin

The physicochemical properties, structural features and immunomodulatory effects of the white asparagus (Asparagus officinalis L.) skin polysaccharides (WASP) were systematically studied. WASP showed a pectic-like structure with a relatively low degree of esterification (DE, 18%); the weight-average molecular weight (Mw) and intrinsic viscosity were 76.1 kDa and 13 mL/g, respectively. Structurally, the dominated sugar residue of WASP was 4-α-D-GalpA (39.7 mol%), while other residues including α-L-Araf, 3-α-L-Rhap, 2,4-α-L-Rhap, and 4-β-D-Galp were also detected with a comparable amount. A proposed structure of WASP was also presented. Physiologically, WASP could modulate the immune response of RAW 264.7 macrophages through increasing the release of immune factors (IL-6, TNF-α and IL-10) and improving the expression of mRNA. To conclude, the pectic-like polysaccharides from white asparagus (Asparagus officinalis L.) skin could be potentially used as an immunomodulatory agent in functional food.