Effects of simulated digestion in vitro on the structure and macrophages activation of fucoidan from Sargassum fusiforme

Molecular size and spatial structure affect the bioactivities of polysaccharides. SFF is a fucoidan extracted from Sargassum fusiforme. The possible changes of SFF affected by gastrointestinal tract and subsequently changes of its physicochemical property or its bioactivity have yet to be systematically investigated. Our results showed that DSFF, the gastrointestinal digestion product of SFF, has increased reducing sugar content, increased proportion of low molecular weight components, and a more clustered island-like morphology. Both SFF and DSFF activate RAW 264.7 macrophages evidenced by the increasing level of NO, intracellular ROS, and macrophages cytokines. Further investigation showed that DSFF induced M1 phenotype polarization in RAW 264.7 cells. DSFF also showed stronger macrophage activation and phenotype polarization than SFF. Our present work showed that SFF could be digested by simulated gastrointestinal environment in vitro and the digested product DSFF showed higher efficiency in macrophages activation and phenotype polarization.