Structural characterization and immunostimulant activities of polysaccharides fractionated by gradient ethanol precipitation method from Panax ginseng C. A. Meyer

Panax ginseng C. A. Meyer is a dual-purpose plant for medicine and food, its polysaccharide is considered as an immune enhancer. Four polysaccharides, WGP-20-F, WGP-40-F, WGP-60-F and WGP-80-F were obtained from ginseng via water extraction and gradient ethanol precipitation with different molecular weights (Mw) of 1.720 x 10(6), 1.434 x 10(6), 4.225 x 10(4) and 1.520 x 10(4) Da, respectively. WGP-20-F and WGP-40-F which with higher Mw and a triple-helix structure are glucans composed of 4-alpha-Glcp, do not show remarkable immunoregulatory effects. WGP-60-F and WGP-80-F are heteropolysaccharides mainly composed of 4-alpha-Glcp and also contain t-alpha-Araf, 5-alpha-Araf and 3,5-alpha-Araf. They are spherical branched conformations without a triple-helix structure and can effectively increase the index of immune organs, lymphocyte proliferation, activate macrophages to regulate the immune system in mice and further enhance immune functions by improving delayed-type hypersensitivity reaction and antibody response. These results indicated that WGP-60-F and WGP-80-F could be used as potential immune enhancers, and gradient ethanol precipitation can be applied for the preparation of ginseng bioactive polysaccharide.