Partial characterization and immunomodulatory activity of polysaccharides from the stem of Dendrobium officinale (Tiepishihu) in vitro

The crude polysaccharide from the stem of Dendrobium officinale (DOP) was obtained by water extraction and ethanol precipitation. Two fractions of DOP, DOP-1 and DOP-2, were fractioned by DEAE cellulose and Sephacryl S-400 gel filtration column chromatography. Their molecular weights and monosaccharide compositions were studied. The immunomodulatory activity of DOP, DOP-1 and DOP-2 was evaluated with in vitro cell models. The results showed that the 533.7 kDa DOP-1 and 159.5 kDa DOP-2 were mainly composed of mannose and glucose. Both DOP and its purified fractions significantly (P < 0.05) promoted splenocyte proliferation, enhanced natural killer cell-mediated cytotoxicity, and increased the phagocytosis and nitric oxide production of macrophages. Moreover, these two fractions caused a significant (P < 0.05) stimulation of cytokine secretion of both splenocytes and macrophages. These findings suggest that Dendrobium officinale polysaccharides should be explored as novel potential immunomodulators.

► The crude polysaccharide and its two fractions were isolated from the stem of D. officinale.
► Their molecular weight and monosaccharide compositions were studied.
► The immunomodulatory activity of three polysaccharides was evaluated with in vitro cell models.
► One fraction DOP-1 exhibited greater effects on lymphocyte activation.
► The other fraction DOP-2 was more effective on macrophage activation.