Isolation, structural characterization and neurotrophic activity of a polysaccharide from Phellinus ribis

A new polysaccharide named PRG was isolated from the fruiting bodies of Phellinus ribis by hot water extraction, ethanol precipitation, anion-exchange and gel-filtration chromatography. PRG was homogeneous, with a molecular weight of 5.16 × 103 Da, as determined by high-performance size-exclusion chromatography-multiangle laser light scattering analysis. Its structural characteristics were investigated and elucidated by methylation analysis, partial acid hydrolysis, gas-liquid chromatography mass spectrometry, Fourier transform infrared and nuclear magnetic resonance spectroscopy. Based on obtained data, PRG was found to be a β-d-glucan containing a (1 → 3)-linked backbone, with a branch of two (1 → 6)-linked and one terminal glucoses substituting at the C-6 position every three residues, along the main chain. PRG exhibited neurotrophic activity, which significantly promoted the neurite outgrowth of the nerve growth factor-stimulated PC12 cells, suggesting that it might be a potential candidate for the treatment of neurodegenerative diseases.