Extraction, optimization and bioactivities of alcohol-soluble polysaccharide from Grifola frondosa

Traditional extraction methods for polysaccharides are water extraction and ethanol precipitation, while the alcohol-soluble polysaccharides would be abandoned. The extraction process of alcohol-soluble polysaccharide from the fungus Grifola frondosa (GFAP) optimized by orthogonal test and the bioactivities (antitumor and antioxidant) were investigated in this study. The optimum extraction conditions were determined as follows: Solid–liquid ratio of 1:20 g/mL, extraction temperature of 65 °C, extraction time of 4.5 h, assistant factors of ultrasound-assisted extraction and extraction times of 2, under these conditions, the experimental yield of GFAP was 36.34 ± 1.26%. High Performance Gel Permeation Chromatography and chemical component analysis showed that the contents of total sugar, protein and uronic acid in GFAP were 95.83%, 0.34% and 0.21%, respectively, and its molecular weight was about 2.9 kDa. Additionally, results of MTT assay showed that GFAP could significantly inhibit the proliferation of Hepatocellular Carcinoma cell line (HepG2) in time- and dose- dependent manners. The in vitro antioxidant results showed that GFAP possessed excellent scavenging effects on ABTS+ (61.2%), DPPH⋅ (90.3%) and HO⋅ (49.2%) at the concentration of 2 mg/mL. These results demonstrated that GFAP is a relatively abundant polysaccahride in Grifola frondosa with strong antitumor and antioxidant activities. Our data provided a theoretical basis for the practical application of GFAP in the future.