Immunostimulatory effects of a polysaccharide from Pimpinella anisum seeds on RAW264.7 and NK-92 cells

Polysaccharides from Pimpinella anisum were isolated using water at elevated temperature and DEAE Sepharose FF chromatography to examine their chemical structure and activation capacity on immune cells. P. anisum fractions (PAF1, PAF2 and PAF3) were mainly composed of neutral sugars (84.0–98.2%) and uronic acids (2.1–11.8%) with weight average molecular weight (Mw) ranging from 186.6 to 5474.5 × 103 g/mol. Polysaccharides induced a significant inflammatory response in RAW264.7 murine macrophage cells releasing nitric oxide and expressing TNF-α, IL-1β, IL-6 and IL-10 cytokines. The induction of NK-92 natural killer cells resulted in TNF-α and IFN-γ production and activation of GrB/perforin-, NKG2D- and FasL-mediated cytotoxicity. Polysaccharides triggered the phosphorylation of NF-κB, ERK, JNK and p38 proteins in RAW264.7 and NK-92 cells indicating the involvement of NF-κB and MAPKs signaling pathways. The most active polysaccharide was a galactoarabinan with complex structure. •A galactoarabinan (PAF2) was isolated from Pimpinella anisum.•Galactoarabinan stimulated RAW264.7 and NK cells to produce proinflammatory mediators.•RAW264.7 and NK cells activated through NF-κB and MAPKs pathways.•Optimum Mw and conformation was essential for cell activation capacity of galactoarabinan.