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

Abstract

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.

Effect of Purified Soluble Polysaccharides Extracted from Gray Oyster Mushroom (Pleurotus sajor-caju (Fr.) Sing.] on 3T3-L1 Adipocytes

“…The hot-water extraction method and purification procedure are modified from our previous report (Sermwittayawong et al 2018). Briefly, polysaccharides in the hot water extract were precipitated using five-volume of absolute ethanol.…”

“…As described in Figure 1, the residue from hot water extraction was further extracted using ammonium oxalate as described previously (Sermwittayawong et al 2018). Briefly, the residue was boiled with 1% ammonium oxalate at 98°C for 3-5 h. The supernatant was collected following centrifugation and precipitated with ethanol.…”

“…Total carbohydrates in the sample was analyzed using the phenol-sulfuric assay (Dubois et al 1951), which was performed as previously described (Sermwittayawong et al 2018).…”

“…Total amount of protein in the sample was determined using Bradford's assay (Bradford 1976), which was performed as previously described (Sermwittayawong et al 2018).…”

“…For the anti-diabetic effect, mushroom polysaccharides have been shown to lower expression of pro-inflammatory cytokines, ameliorate glucose intolerance, insulin resistance and oxidative stress in mice (Kanagasabapathy et al 2012). In tissue culture, we have previously shown that both crude and purified polysaccharides isolated from the gray oyster mushroom stimulated glucose uptake in L6 myotubes (Jantaramanant et al 2014;Sermwittayawong et al 2018) including cellular glucose uptake. Although cumulative evidence in literature suggests a connection between β-glucan and reduction of blood glucose concentration, a mechanism of how β-glucan affects cellular glucose uptake has not been demonstrated.…”