Effects of invitro digestion on the composition of flavonoids and antioxidant activities of the lotus leaf at different growth stages

The lotus leaf is rich in phenolic compounds and has good antioxidant activity. The effects of simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) digestions on the active substances and antioxidant activity of the lotus leaf in different growth stages (D25, D45 and D65) were investigated. The total phenolic content of D25 and D45 significantly increased by SGF digestion but not D65 compared to the DW treatment. However, SIF treatment saw markedly increased total phenolic content across all growth stages (D25, D45 and D65). Moreover, the total flavonoid content at all growth stages was increased by SIF digestion compared to SGF treatment. The pepsin and trypsin had different effects on the FRAP and ABTS (2, 2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid)) antioxidant activities of the lotus leaf. The SGF digestion increased the FRAP antioxidant capacity of the lotus leaf, and SIF digestion increased the ABTS antioxidant capacity of the lotus leaf. The HPLC results showed that the main flavonoid compound in the lotus leaf was isoquercetin. This study provides a theoretical basis for the development and utilisation of the lotus leaf as an inexpensive natural and functional food ingredient.