Comparative study of the inhibitory effects of lotus seedpod oligomeric procyanidins on dietary AGE released from glycated casein during digestion

Glycation of protein results in the formation of advanced glycation end-products (AGEs), which are further absorbed by the body through digestion in the gastrointestinal tract. The inhibitory properties of procyanidin for the release of AGEs from glycated proteins are of great significance in promoting, accelerating or stabilizing gastrointestinal folding intermediates, although the mechanism of action remains unclear. With the background of dairy processing, the study investigated the inhibitory effect of lotus seedpod oligomeric procyanidins (LSOPC) and its three monomers on AGE release from glycated casein (G-CS) during gastrointestinal digestion. In gastrointestinal microenvironments, multispectral and microscopy analysis were used to investigate interaction mechanisms. Results showed that the binding force of the protein-procyanidin complexes were hydrogen bonding and hydrophobic interaction and LSOPC leaded the G-CS secondary structure transformations furtherly. In the gastric environment, all monomers displayed stronger binding to pepsin but in the intestinal environment, results were opposite. Molecular docking showed that procyanidins were bound in the internal cavity of G-CS, pepsin and pancreatin, thereby forming a relatively stable binding conformation. Moreover, procyanidins enhanced the antioxidant capacity of G-CS, which could attenuate postprandial oxidative stress in the gastrointestinal tract caused by the release of AGEs. Together, this study improves our understanding of dietary AGEs during gastrointestinal digestion.