Structural features and immunostimulating effects of three acidic polysaccharides isolated from Panax quinquefolius

Three acidic polysaccharides (PPQA2, PPQA4 and PPQA5) were successfully purified from the water-extracted crude polysaccharides of Panax quinquefolius by combination of DEAE Sepharose and Sephacryl S-300 chromatography. The average molecular weights (Mws) of PPQA2, PPQA4 and PPQA5 were 2.3 × 104 Da, 1.2 × 105 Da, and 5.3 × 103 Da, respectively. Monosaccharides components analysis indicated that PPQA2 and PPQA5 were composed of arabinose, rhammose, mannose, galactose, glucose, galacturonic acid and glucuronic acid in a molar percent of 8.0:4.0:2.9:7.2:12.5:26.6:38.8 and 8.5:3.2:5.3:10.8:32.4:15.5:24.4. PPQA4 was composed of arabinose, rhammose, mannose, galactose, glucose and glucuronic acid in a molar percent of 19.7:5.1:8.1:23.9:41.3:2.0. The 13C NMR spectra indicated the existence of O-acetyl groups in PPQA2 and PPQA5, while absence in PPQA4. The in vitro study showed that PPQA2, PPQA4 and PPQA5 were all able to stimulate the production of secretory molecules (NO, TNF-α, and IL-6) of RAW264.7 murine macrophages in a dose-dependent manner. These findings suggest that the three acidic polysaccharides isolated in our study have immunopotentiating effects on macrophages and should be used as a beneficial health food.