The composition and bioactivity of bound polyphenols from coffee dietary fiber during in vitro Simulating digestion

Dietary fiber from coffee peel is rich in bound polyphenols good for human health due to the antioxidant activity. In this study, we evaluated the bound polyphenol release conditions and activities in coffee peel soluble dietary fiber (CPSDF) in the process of in vitro simulation digestion. The CPSDF structure became loose and porous due to simulated digestion but retained the polysaccharide backbone. Widely-targeted metabolomics analysis identified 550 metabolites, with phenolic acids and flavonoids being main differentially expressed metabolites in digested products (82.18% in total). The most significant increase in the 5,7,8,3',4'-pentamethoxyflavanone content and decrease in the 3,5-dihydroxyacetophenone content were observed after digestion (undigested vs S-intestine). Additionally, the changes in antioxidant and enzyme inhibitory activities followed the same pattern as that observed for total phenolic content. The enzyme inhibitory and antioxidant activities of gastric digestion products were greater than those of the oral and small intestinal digestion products. The present work provided the theoretical foundation for developing high-value CPSDF products and reusing coffee peel waste.