Purification, initial characterization and immune activities of polysaccharides from the fungus, Polyporus umbellatus

Polyporus umbellatus (formerly Grifola umbellatus), an edible fungus, has been used as traditional Chinese medicine. The present investigation aimed to uncover the active ingredients in this fungal species, with the emphasis on its polysaccharides. Two polysaccharides, one from fermented mycelium and the other from the fruiting body, were chromatographically purified. Molecular weights, anti-microbial and immune activities of the polysaccharides were determined. The mycelium polysaccharide was found to have a molecular weight of 857 kDa and consist of glucose and galactose at a molar ratio of 1.57:1, while the one from the fruiting body, 679 kDa in molecular weight, was also made up of glucose and galactose but at a molar ratio of 5.42:1. In immune assays, these fungal polysaccharides increased the killing potency of natural killer (NK) and lymphokine-activated killer (LAK) cells from mouse spleen and promoted proliferation of mouse B and T cells. Additionally, both P. umbellatus mycelium and its extract were found to inhibit Escherichia coli and Staphylococcus aureus, but had no effects on Aspergillus niger or Aspergillus nidulans. These results indicated that fermented P. umbellatus mycelium is indeed immune active, most probably due to its ingredients of polysaccharides. The consumption of this fungus may be beneficial for human health.