Structural properities and immunoenhancement of an exopolysaccharide produced by Phellinus pini

Phellinus pini exopolysaccharide (PPE) is a mannan produced by P. pini when cultured in potato dextroseagar medium. Partial hydrolysis with acid, periodate oxidation and Smith degradation, methylation and ¹³C nuclear magnetic resonance (NMR) spectroscopy were used to elaborate its structure. Results indicated that PPE contained a backbone of (1→2)-linked Man, which was heavily substituted via (1→6)-glucosidic bonds with (1→3)-linked Man, and terminated mainly with Man, as well as a small amount of Gal and Glc. Immunological tests showed that PPE exhibited high macrophages-activating ability, thereby augmenting phagocytosis and enhancing the production of nitric oxide, tumour necrosis factor-α and reactive oxygen species. Therefor, PPE had potential applications in developing functional food or in serving as a natural immnunostimulant.