Stability and antioxidant activity of 10 isoflavones and anthocyanidins during in vitro digestion

The stability and antioxidant activity changes of 10 phytochemicals (isoflavones: genistein, genistin, daidzein, daidzin, formononetin, and anthocyanidins: delphinidin, cyanidin, pelargonidin, malvidin, petunidin) and food representatives (soybeans and blueberries) during in vitro digestion were investigated. Results indicated that the stability of isoflavones and anthocyanidins decreased with digestion. Among the isoflavones, the loss rate of formononetin was the largest, reaching 98.24%, and that of daidzein was the smallest (22.78%). And after intestinal digestion, anthocyanidins degraded into phenolic acids and other compounds, and the loss rate was above 95%. The loss of phenolic compounds in food extract was smaller than the standards, and the loss rate of phenolic compounds in hydrolyzed blueberry extracts (90.66%–96.04%) was higher than that of soybean extract (31.22%–59.74%). Moreover, the antioxidant activity of isoflavones and anthocyanidins decreased after the oral phase. During the gastrointestinal phase, the ABTS, DPPH and FRAP of isoflavones increased, while the ORAC and CAA decreased. The antioxidant activity of anthocyanidins increased in the gastric digestion and decreased in the intestinal phase. The glucoside linkage in the A ring and the hydroxyl methoxylation in the B ring weakened the antioxidant activity of isoflavones, while the hydroxylation and methoxylation of B rings of anthocyanidins could enhance thier antioxidant activity. The changes in antioxidant activity of the two food extracts were consistent with their contents.