Immunomodulatory activity-guided isolation and characterization of a novel polysaccharide from Atractylodis macrocephalae Koidz.

The Rhizoma of Atractylodis macrocephala Koidz. is a traditional Chinese herbal medicine that has been widely and empirically used for unexplained recurrent spontaneous abortion. In this study, a polysaccharide from the Rhizoma of Atractylodis macrocephala Koidz., designated as RAMP2, with an absolute molecular weight of 4.354 × 103 Da was isolated and found to be composed of mannose, galacturonic acid, glucose, galactose and arabinose. The NMR results displayed that →3-β-glcp-(1→, →3,6-β-glcp-(1→, →6-β-glcp-(1→, T-β-glcp-(1→, →4-α-galpA-(1→, →4-α-galpA-6-OMe-(1→, →5-α-araf-(1→, →4,6-β-manp-(1→ and →4-β-galp-(1→ were the main linkages in RAMP2. TEM and SEM results indicated that RAMP2 was globular in structure. Furthermore, in vitro experiments on murine CD4+ T cells revealed that RAMP2 could increase the percentage of Treg cells, up-regulate Foxp3, IL-10 and IL-2 mRNA expressions and the secretion of IL-10 and IL-2. RAMP2 was further shown to increase STAT5 phosphorylation levels in Treg cells, suggesting that RAMP2 increased the number of Treg cells through IL-2/STAT5 pathway.