Effects of simulated digestion on the structural characteristics and dendritic cell activation of longan polysaccharides

An active polysaccharide (LP) from longan was purified and characterized. LP consisted of galactose and glucose in a molar ratio of 1.5: 98.5, with a molecular weight of 4.67 × 107 g/mol. The main backbone of LP was T-α-D-Glcp-[(1 → 6)-α-D-Glcp-(1 → 6)-α-D-Glcp]n. After simulated gastrointestinal digestion, the molecular weight distribution, monosaccharide composition, and major glycosidic bonds of LP were not significantly changed. LP and digested LP (DLP) reduced phagocytosis and promoted IL-10 and IL-12 secretion of dendritic cells. In addition, the effects of LP and DLP on activating dendritic cells showed no significant difference. This study helps to illuminate the potential mode of immunomodulatory action of longan polysaccharides in vivo.