Structural properities and immunoenhancement of an exopolysaccharide produced by Phellinus pini

- Exopolysaccharide PPE was isolated from the culture medium of Phellinus pini..
- Structure and immunoregulatory activity of PPE were investigated.
- PPE was a mannan consisting 2- and 2, 6-α-d-Manp in its backbone.
- 3-α-d-Manp formed its side chains.
- PPE exhibited an obvious macrophage-activating effect.

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.