Pumpkin polysaccharide preparation, simulated gastrointestinal digestion, and in vivo biodistribution

We employed a single factor and response surface methodology based on Box-Behnken design (BBD) to optimize the extraction of pumpkin polysaccharides. We then simulated pumpkin polysaccharide gastrointestinal digestion in vitro and investigated their biodistribution in mice. The optimal extraction conditions, with a yield of 7.38 ± 0.21%, were as follows: a concentration of NaOH 1.20%, a ratio of material to liquid of 1:11, and an extraction time of 2.1 h, respectively, according to single factor and BBD experiments. In the gastrointestinal experiment in vitro, the molecular weight of the polysaccharides markedly decreased after gastric digestion for 30 min, suggesting the decline is due to the breakdown of polysaccharide glycosidic bonds. The simulated intestinal fluid had little effect on polysaccharides digestion within 240 min. Analysis of the biodistribution in mice indicated that the polysaccharides distribute in the duodenum, jejunum, and ileum 30 to 60 min after intragastrical administration, and are absorbed in the jejunum and ileum after 60 to 360 min. These results provide information on the digestion and biodistribution of pumpkin polysaccharides and offer a theoretical basis for further understanding the absorption mechanisms in vivo.