Polyphenol-rich extract of Chinese sumac (Rhus chinensis Mill.) fruits and its main component decrease in vitro starch digestibility of bread: Exploring the potential mechanisms from the perspective of molecular interactions

This study intended to examine whether the polyphenol-rich extract of Chinese sumac fruits (PREF) and its main component quercitrin can delay the in vitro starch digestibility of bread and unravel the underlying mechanisms. The findings indicated that PREF or quercitrin fortification, especially a high dose of PREF (50 g/kg of flour), altered the texture and surface morphology of bread and reduced its digestibility. In vitro inhibiting starch digesting enzymes and in silico analyses were performed to unveil the underlying mechanisms. Both PREF and quercitrin significantly inhibited the activities of α-glucosidase and α-amylase, which could be attributed to the fact that quercitrin can effectively enter the active site of enzymes and form a stable complex. Moreover, the major polyphenols in PREF formed a stable complex with the starch chain, which reduced its digestibility. These encouraging results signify that PREF fortification may be used to develop new healthy bread products for patients with diabetes.