Biotransformed citrus extract improves intestinal barrier integrity and reduces oxidative damage in female Drosophila melanogaster

Citrus bioflavonoids are widely studied for their potential to strengthen the intestinal barrier and to reduce oxidative damage. However, there is limited knowledge on the bioavailability of flavonoids and its impact on the antioxidant capacity of these nutrients in living organisms. For this study, we tested potential health-promoting effects of aqueous extracts of Citrus aurantium var. amara L., Citrus sinensis, Citrus paradisi powder (AQE) rich in naringin and hesperidin and its bio-transformed version submitted to citric acid hydrolysis and fermentation (FermCAE) rich in naringenin and hersperitin in the in vivo model Drosophila melanogaster. To test the influence of AQE and FermCAE on intestinal barrier integrity, 5 d. o. female w1118 fruit flies were challenged with dyed 5% dextran sodium sulphate solution for 7 days. Dead flies, as well as those that expressed Smurf phenotype were scored throughout 3 independent experiments. Furthermore, oxidative stress challenge was performed. Therefore, 30 mM iron (II) sulphate was added to the solid food and introduced to the test subjects for 3 biochemical assays (ROS level, MDA content and metabolic activity), mortality and climbing activity tests, respectively. In both sets of experiments D. melanogaster were divided into control groups (no stressor or flavonoids), stressor only group and treatment groups with stressor and one of the tested extracts (AQE, FermCAE) in 2 different concentrations (2.5%, 5% (v/w)). Our results suggest that the biotransformation of the glycosides naringin and hesperidin into the aglycons naringenin and hesperitin has significantly improved their protective effect against intestinal barrier damages of in a dose-dependent manner. Furthermore, we observed significant reduction of ROS level in flies stressed with iron sulphate and treated with citrus flavonoid extracts, with most antioxidant effect observed in the group treated with 5% FermCAE. Significant positive impact of AQE and FermCAE was also observed in terms of survivorship and climbing activity of fruit flies exposed to oxidation-inducing stressor. We conclude that supplementation with fermented citrus flavonoids extract improves survivorship, intestinal integrity, and climbing activity in D. melanogaster upon various stressors.