Structural Characterization And Chemical Modification Of Polysaccharide GF4A From Grifola Frondosa

Grifola frondosa, a highly regarded edible fungus, has many pharmaceutical activities, such as anticancer, antiviral and enhancing immunity of human body. In this paper, a water-insoluble polysaccharide fraction GF4A is extracted from fermented Grifola frondosa mycelia using different kinds of separation and purification methods. The primary structure of GF4A is determined by chemical and modem instruments analysis techniques. The structure-defined polysaccharide is further modified by chemical methods, and the anti-rumor activity of one derivative is evaluated.The fermented Grifola frondosa mycelia are first extracted by ethanol, hot water, cool alkali and hot alkali; two water-insoluble fractions GFM2 and GFM5 are acquired. GFM2 is further purified by low-pressure gel-permeation chromatography (LPGPC) and a pure polysaccharide GF4A has been got. The molecular weight of GF4A is estimated as 109kD by HPLC-GPC and the sugar contend is about 95.4%.The primary structure of GF4 A is elucidated by chemical methods, such as acid hydrolysis, TLC, GC, periodate oxidation, Smith degradation, methylation, congo red binding, acetyl oxide hydrolysis, and IR, UV, NMR etc. spectroscopic techniques. GC analysis showed that GF4A contains glucose, mannose, xylose, with the molar ratio of 9:2:1. The backbone of GF4A is consisted of ct-l,3-D-Glc and a-l,3-D-Man, with the molar ratio of 3:1; every eight sugar residues of the backbone consist a repeating unit; two branches located at O-4 of a-l,3-D-Glc, one is consisted of three |3-l,4-D-Glc and the other is a