Effect of in vitro digestion of Cudrania cochinchinensis root extracts on phenolic compounds, bioactivity, bioaccessibility and cytotoxicity on HepG2 cells

The study aimed to investigate the bioaccessibility and the stability of purified ethanol extracts (PEE) from Cudrania cochinchinensis roots, and the changes in antioxidant activity and enzyme inhibition activity and cytotoxicity by in vitro digestion. No compounds were lost during the gastrointestinal digestion (GID) process, 15 compounds were tentatively identified using UPLC-TOF-MS/MS technology, including five phenolic and ten flavonoid compounds. After the gastric digestion (GD), the bioaccessibility of phenolic and flavonoid compounds was 55.66% and 52.44%, respectively. After the intestinal digestion (ID), the bioaccessibility of phenolic and flavonoid compounds reduced to 39.70% and 33.36%, respectively. The gastrointestinal digestion (GID) decreased the bioaccessibility of phenolic compounds. All compounds were affected throughout the gastrointestinal digestion (GID), among which the more affected compounds were 4-hydroxybenzoic acid, eriodictyol-7-O-glucoside, resveratrol and 3,6,3’,4’-tetrahydroxyflavone (compared with the peak intensity of the undigested PEE). Furthermore, there was a reduction in the antioxidant activity, inhibition activity against α-glucosidase and tyrosinase, and cytotoxicity toward HepG2 cells of the PEE after GID. There was a significantly positive correlation between the bioactivity and the total phenolic/flavonoid contents. The results showed that in vitro digestion had significant effects on the phenolic content and bioactivity. Although phenolic contents were decreased during GID, C. cochinchinensis roots is still a good source of bioactive compounds for the development of functional foods with health benefits.