Purification, characterization, and biological activities of purified polysaccharides extracted from the gray oyster mushroom [Pleurotus sajor-caju (Fr.) Sing.]

Gray oyster mushroom, a common edible mushroom in Thailand, has been used as a source for polysaccharide extraction and purification. In this study, we extracted polysaccharides from the gray oyster mushroom through hot water, ammonium oxalate, and alkaline extraction methods. The extracts were further purified using enzymatic digestion, solvent extraction, and column chromatography. Fourier-transform infrared spectroscopy reveals that the selected fractions contain β-(1→3) glucan and mannan. Monosaccharide composition analysis suggests that glucose and mannose are the major constituents of all analyzed fractions. Interestingly, only the gel-like fraction, namely SG1-1 could enhance neutrophils’ killing activity on Candida albicans. In addition, the purified fractions stimulated glucose uptake activity in the L6 myotubes in a dose-dependent manner. Practical applications The ability of those polysaccharides to stimulate glucose uptake in the muscle cells and enhance a neutrophil’s killing activity implicates the antidiabetic and immunostimulatory activities, respectively. Thus, these polysaccharides could be potentially developed into an immunostimulating agent and an alternative medicine for treating diabetes mellitus.