Purification, structural characterization, and immunomodulatory activity of two polysaccharides from Portulaca oleracea L.

In present study, two water-soluble polysaccharides designated as POL-1 and POL-2 were purified from purslane and their structural characteristics as well as immunomodulatory activity were investigated. The weight-average molecular weight ( M w ) of POL-1 and POL-2 were determined to be 64,100 Da and 21,000 Da, respectively. Comprehensive techniques including UV, IR, GC–MS, and NMR were applied to deduced that POL-1 was a pectin polysaccharide homogalacturonan (HG) consisting of →4)- α -Gal p A-(1→ with methyl ester degree of 9.71 % and acetylation degree of 0.34 %, while POL-2 was composed of a 1, 4-linked β -Gal p backbone substituted by short side chain →4)- α -Glc p -(1→ and →6)- α -Glc p -(1→. The →4)- α -Glc p -(1→ was attached at the O -6 position of →4)- β -Gal p -(1→. TEM further revealed that POL-1 was non-branched single chains, while POL-2 was entangled microstructure with side chains. Moreover, POL-2 significantly promoted macrophage phagocytosis as well as the secretion of NO and cytokines (TNF- α , IL-6) through activating NF-κB signaling pathway, thus demonstrating potential immunomodulatory activity. These findings suggested that purslane may be exploited as a potential adjuvant and dietary supplement with immunostimulatory purpose.