Systematic evaluation of polyphenols composition and antioxidant activity of mulberry cultivars subjected to gastrointestinal digestion and gut microbiota fermentation

In this study, mulberry cultivars were found to have abundant bioactive compounds such as phenolics (100.97-586.23 mg gallic acid equivalents/100 g fresh weight), flavonoids (16.38-368.16 mg rutin equivalents/100 g fresh weight) and procyanidins (4.20-121.56 mg catechin equivalents/100 g fresh weight) after in vitro digestion. HPLC-TOF-MS analysis revealed that digested mulberry cultivars contained multiple phenolic compounds including cyanidin-3-O-glucoside and cyanidin-3-O-rutinoside. After gut microbiota fermentation, the contents of anthocyanins were increased initially, then decreased with time, and some anthocyanin metabolites (such as 3,4-Dihydroxybenzoic acid, 2,4,6-trihydroxybenzoic acid, 2,4,6-trihydroxybenzaldehyde, etc.) were detected. Our further cellular study indicated that mulberry (Hanguo) possessed reactive oxygen species scavenging capacity after gut microbiota fermentation. Our results indicated that the new cultivar Hanguo contained abundant polyphenols and exhibited potent antioxidant property after in vitro digestion and gut microbiota fermentation compared with other mulberry cultivars, which could be recommended as a dietary source of functional foods.