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 × 104 Da. While, ALRPN-2 was composed of glucose, galactose and mannose with Mw of 5.105 × 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-α) and interleukin (IL-6, IL-1β), 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 anti-inflammatory activities. Our study would provide theoretical support for potential applications of Apocynum venetum L. during traditional use and the health care fields.