Changes of Polyphenol and Flavonoid Contents and Antioxidant Activities of Five Edible Flowers during Simulated Digestion in Vitro

Objective: To explore the changes of phenolic substances and antioxidant activities of five edible flowers after simulated gastrointestinal digestion in vitro. Method: Five flower include osmanthus, marigold, gardenia, magnolia, hibiscus as the research material, by comparing the content of polyphenols and flavonoids and their in vitro antioxidant activities before digestion, in vitro simulated gastric digestion, and in vitro simulated intestinal digestion. Results: The contents of flavonoids, polyphenols and antioxidant activities of the five edible flowers did not increase significantly in the simulated gastric digestion stage, but showed a larger increase trend in the simulated intestinal digestion stage. Through the whole simulated gastrointestinal digestion, polyphenols increased by 127.55% (osmanthus)~461.70% (marigold), and flavonoids increased by 46.50% (magnolia)~218.46% (marigold). Among which, the highest content of polyphenols and flavonoids were found in marigold with the value of (8.95±0.03) mg gallic acid equivalent (GAE)/g and (83.01±0.01) mg catechin equivalent (CE)/g, respectively. Among the three antioxidant activities, the DPPH free radical scavenging ability increased by 77.0% (hibiscus)~158.05% (gardenia), the ferric ion reducing antioxidant power increased 15.30% (osmanthus)~163.92% (gardenia), ABTS⁺ free radical scavenging ability increased by 142.35% (magnolia)~274.18% (gardensis). Conclusion: Five edible flowers had good bioavailability potential and would be expected to be used as raw material sources of natural antioxidant functional foods.