Digestive behavior of Dendrobium huoshanense polysaccharides in the gastrointestinal tracts of mice

With fluorescent end-labeling method, a homogenous Dendrobium huoshanense polysaccharide (GXG) that was orally administrated to mice was found to be degraded into a stable fragment (dGXG) in the stomach, where dGXG was propelled into the small intestine and absorbed into the systemic circulation. The residual GXG in the stomach could pass through the gastrointestinal tract and was excreted into faeces with a very slow fermentation in the large intestine. The simulated digestion of GXG indicated that the acidic pH condition in the gastric fluid was responsible for GXG degradation, which was supported by the oral digestion of dGXG. Chemical analysis not only showed a change in the molar ratio of monosaccharide compositions and glycosidic linkage types, but also found the loss of the sugar residue (1 → 4)-linked Galp after the acid treatment of GXG, suggesting that the cleavage of glycosidic linkage, especially (1 → 4)-linked Galp linkage, resulted in GXG degradation in the gastrointestinal tract.