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 (Mw) 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)-alpha-GalpA-(1 -> with methyl ester degree of 9.71 % and acetylation degree of 0.34 %, while POL-2 was composed of a 1, 4 -linked beta-Galp backbone substituted by short side chain -> 4)-alpha-Glcp-(1 -> and -> 6)-alpha-Glcp-(1 ->. The -> 4)-alpha-Glcp-(1 -> was attached at the O-6 position of -> 4)- beta-Galp-(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-alpha, IL -6) through activating NF-kappa B 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.