Phytochemical bioaccessibility and in vitro antidiabetic effects of Chinese sumac (Rhus chinensis Mill.) fruits after a simulated digestion: insights into the mechanisms with molecular docking analysis

This work studied the effects of gastrointestinal digestion on the phytochemical bioaccessibility and in vitro anti-diabetic effects of different fractions from Chinese sumac fruits and delineated the underlying mechanisms by molecular docking. Results showed that gastric digestion significantly increased the phytochemical bioaccessibility and inhibitions for α-glucosidase, dipeptidyl peptidase-4 (DPP-IV) and advanced glycation end product (AGE) formation of the ethanol-extracted fraction, whereas intestinal digestion remarkably decreased these parameters (P < 0.05). For the free phenolic fraction, the parameters were remarkably reduced after gastric digestion but significantly increased after intestinal digestion (P < 0.05). Quercitrin and gvajaverin contributed the most to the α-glucosidase and DPP-IV inhibitions, and trigalloyl glucose and its isomer could be the primary bioactive substance responsible for AGE suppression. Quercitrin, the predominant phenolic compound, could effectively interact with crucial amino acid residues in α-glucosidase, DPP-IV and bovine serum albumin with hydrogen bonds and hydrophobic interactions to exert its inhibitions.