Extraction, purification and structural characterization of polysaccharides from Apocynum venetum L. roots with anti-inflammatory activity

To investigate anti-inflammatory effects and molecular mechanisms of polysaccharides derived from Apocynum venetum L. roots on lipopolysaccharide (LPS)-induced mouse mononuclear macrophage leukemia (RAW 264.7) cells based on their structural characterization. Water soluble polysaccharides (ALRP) purified from Apocynum venetum L. roots were processing by diethylaminoethyl (DEAE)-cellulose, Sepharose CL-6B or Sephadex G100, and semi-preparative high performance gel permeation chromatography (HPGPC), successively. After that, two neutral homogeneous heteropolysaccharides (ALRPN-1 and ALRPN-2) were obtained. Of which, ALRPN-1 was composed of glucose, galactose and arabinose with weight-average molecular (Mw) of 1.542 x 104 Da. While, ALRPN-2 was composed of glucose, galactose and mannose with Mw of 5.105 x 103 Da. Structural characterization suggested that ALRPN-1 and ALRPN-2 had similar linear backbone with different branches. Meanwhile, the senior structure and micromorphology of ALRPN-1 and ALRPN-2 were demonstrated different. Furthermore, they exerted potent anti-inflammatory activities by weakening the phagocytosis to a certain extent, significantly reducing the level of nitric oxide (NO), tumor necrosis factor (TNF-alpha) and interleukin (IL-6, IL-18), as well as down-regulating the phosphorylation level of extracellular signal-related kinase (ERK1/2) of mitogen-activated protein kinases (MAPKs) signal pathway in LPS-induced RAW 264.7 cells. This study systematically analyzed the two new neutral polysaccharides purified from Apocynum venetum L. roots and demonstrated their potent antiinflammatory activities. Our study would provide theoretical support for potential applications of Apocynum venetum L. during traditional use and the health care fields.