Purification, characterization and biological activity of a novel polysaccharide from Inonotus obliquus

A novel water-soluble polysaccharide IP3a was successfully isolated and purified from I. obliquus by DEAE-cellulose, Sepharose CL-6B and Sephadex G-200 column chromatography. Chemical characterization and antitumor and immunoregulatory activity of IP3a were investigated. IP3a consisted of rhamnose, arabinose, glucose and galactose in a molar ratio of 2.5:4.6:1.0:2.6 with an average molecular weight of 48,820 Da. IP3a exhibited no significant antitumor activities in vitro. However, IP3a could not only inhibit the growth of transplantable Jurkat tumor in mice significantly, but also could enhance the splenocyte proliferation and lymphocyte proliferation induced by ConA and LPS in a dose-dependent manner. At the same time, IP3a could promote cytokine secretion (IL-2, IL-6, IL-12 and TNF-α) and macrophage phagocytosis in mice. In addition, IP3a could increase Bax expression and inhibit Bcl-2 expression significantly. These results suggested that antitumor mechanisms of IP3a might be associated with improving immune response in vivo and inducing apoptosis of tumor cells in vitro. IP3a might be utilized as a potential therapeutic agent against lymphoma cancer with immunomodulatory activity.