Abstract: Objective: To explore the immunoactivity of Grifola frondosa fruit body polysaccharides (GFP) with different relative molecular weights. Methods: Three polysaccharide fractions from Grifola frondosa fruit body named as GFP-I (＜ 50 kD), GFP-II (50－100 kD) and GFP-III (100－200 kD) were prepared by microwave-assisted extraction followed by multi-enzyme hydrolysis and purified by ultrafiltration. The proliferation of murine lymphocytes with and without Con A or LPS induction in virto was evaluated by MTT assay. A S180 tumor-bearing mouse model was established, and the inhibitory effect of the three GFP fractions at different concentrations on tumor growth was also explored. Results: Lymphocyte proliferation rate without induction was increased by 26.558%－74.167% (P ＜ 0.001), 20.175%－152.075% (P ＜ 0.001) and 26.473%－334.797% (P ＜ 0.001), respectively in group GFP-I, GFP-II and GFP-III as compared with RPMI-1640 group, Con A-induced lymphocyte proliferation rate exhibited respective increases of 31.408%－122.894% (P ＜ 0.001), 53.075%－235.693% (P ＜ 0.001) and 83.347%－367.241% (P ＜ 0.001) for group GFP-I, GFP-II and GFP-III, and LPS-induced lymphocyte proliferation rate was increased by 20.526%－97.075% (P ＜ 0.001), 38.288%－211.348% (P ＜ 0.001) and 54.454%－344.883% (P ＜ 0.001), respectively. In comparison with NS group, the inhibitory rates of GFP-I, GFP-II and GFP-III on tumor growth in S180 tumor-bearing mice were 10.15%－22.94% (P ＜ 0.001), 12.79%－30.10% (P ＜ 0.001) and 23.86%－51.65% (P ＜ 0.001), respectively. Conclusion: GFP-I, GFP-II and GFP-III have notable immunoactivity and anti-tumor activity and the activity of GFP-III is the strongest and positively related to its concentration. Further, these three polysaccharides might mainly promote the T lymphocyte proliferation.

Key words: Grifola frondosa polysaccharides, microwave-assisted extraction followed by multi-enzyme hydrolysis, ultrafiltration, immunoactivity, inhibitory rate of tumor growth