Extraction, purification, structure and bioactivities of polysaccharides from Grifola frondosa (maitake): a review

Grifola frondosa is an edible and medicinal mushroom, and modern pharmacological studies have revealed that it possesses various beneficial activities, which are owing to its complex bioactive components. Among them, polysaccharides are the primary active component of G. frondosa. Although numerous researchers have studied G. frondosa in recent decades, there is currently no review available concerning the polysaccharides of this mushroom. In this paper, we first summarized the methods for extracting and purifying the polysaccharides of G. frondosa polysaccharides. The extraction of polysaccharides directly affects their purity, which in turn affects their bioactivities. Hot water is the common method uesd to extract polysaccharides from this mushroom. Scientists have also developed some new extraction methods, such as cold water extraction, the ammonium sulfate/ethanol aqueous two-phase system (ATPS) and supercritical CO2 extraction. The extracted crude polysaccharides are usually accompanied by compounds, such as proteins, fats and pigments, which can interfere with the structural identification and subsequent activity analyses. Therefore, further separation and purification of the polysaccharides are necessary. The common purification methods of polysaccharides are ethyl alcohol deposition and column chromatography. Next, we reviewed the molecular weights, monosaccharide compositions, structural characteristics and biological activities of G. frondosa polysaccharides. The polysaccharides had a variety of biological activities, such as anti-tumor, antioxidant, hypoglycemic and hypolipidemic activities among others. This paper will provide useful references for the investigation, production, and application of G. frondosa polysaccharides in functional foods and as therapeutic agents.