Monosaccharide Composition Analysis of Immunostimulating Subfraction from Auricularia auricula-judae Hot Water Extract

Auricularia auricula-judae hot water extract (AACE) was previously demonstrated the immunestimulating effects by initiating macrophage activation toward M1 phenotype. The subfractions of different molecular weight of AACE exhibited different potency in the immune stimulation. The components of molecular weight between 10 to 50 kDa, assigned as F2, exhibited the highest capability in the immune stimulation which associated with increase of anti-cancer efficacy of macrophages and might be a potential dietary adjuvant for cancer immunotherapy. Polysaccharides are major immunostimulating components of most species of edible fungi. Hence, in the present study, the characteristics of polysaccharides contained in the F2 fraction of AACE were further elucidated. The monosaccharide compositions and glycosidic linkages were determined using high performance liquid chromatography (HPLC), ultraperformance liquid chromatography-electrospray tandem mass (UPLC-MS/MS) spectrometry and nuclear Magnetic Resonance (NMR) spectroscopy. The results indicated that F2 fraction contained mainly gluconic acid, mannose, glucose, xylose, rhammnose and N-acetylglucosamine, whereas mannose and gluconic acid were not detected in the fraction of molecular weight lower than 10 kDa that was previously demonstrated to have limited immune-modulating activity. The F2 fraction contained gluconic acid, mannose, glucose, xylose, rhammnose and N-acetylglucosamine in a molar ratio of 1.0:5.6:5.8:6.4:6.9:19.0 and had the highest molar ratio in N-acetylglucosamine compared with the other subfractions of AACE. NMR spectroscopy revealed the presence of the glycosidic linkages of -2)[β-D-GlcA-(1-3)β-D-Glc-(1-3)][α-D-GlcNAc-(1-4)]α-D-Man-(1-2) β-D-Xyl-(1-2)α-D-Rha(1- and main chain of α-D-Man-(1-2)β-D-Xyl-(1-2)α-D-Rha in F2 components. Our study provides fundamental information required for chemistry study and nutraceuticals development for the immunostimulant components of A. auricula-judae.