Abstract: The effects of three simulated digestive juices on the in vitro digestion of submicron and common powders, water and alcohol extracts, and crude dendrobine and polysaccharide from Dendrobium nobile Lindl. stems were investigated by using a model gastrointestinal system. The dissolution rates of dendrobine and polysaccharide were evaluated. By using high performance liquid chromatography (HPLC), 3,5-dinitrosalicylic acid method and iron exchange chromatography, we determined the changes in the molecular weight, reducing sugar content and monosaccharide composition of polysaccharide after digestion. The polyphenols in digestive juices were analyzed by ultra-high performance liquid chromatographytandem mass spectrometry (UPLC-MS-MS). Results showed increasing dissolution rate of dendrobine during digestion. Submicron powder digestion showed the highest dendrobine dissolution rate of (21.46 ± 0.52)%. On the contrary, the lowest dissolution rate of (8.74 ± 0.50)% was observed for the crude dendrobine. The dissolution rate of polysaccharide from the water extract was the highest among all the samples. Furthermore, during oral and gastric digestion, the submicron powder showed a higher dissolution rate of polysaccharide compared to the common powder, whereas the opposite was observed during intestinal digestion. In addition, simulated gastrointestinal digestion reduced the molecular weight of polysaccharide, and increased reducing sugar content, but did not produce any monosaccharides. The polyphenols from Dendrobium nobile Lindl. showed an increasing trend in simulated gastric juice, but generally decreased in simulated intestinal juice.

Key words: Dendrobium nobile Lindl., in vitro digestion, dendrobine, polysaccharides, polyphenols