Micellization of soy extract improves bioavailability of glycosidic isoflavones daidzin, glycitin and genistin in a model organism Drosophila melanogaster

Isoflavones are bioactive flavonoids that are naturally occurring in soybeans and foods containing soy. These phytochemicals are also known as phytoestrogens due to their oestrogen mimicking nature, while also possessing some other health promoting capabilities, such as antioxidant properties, positive impact on weight and cardio system in humans and various model organisms. Naturally isoflavones occur in soybeans prevalent as 7-O-glycosides with sugar moieties that are decreasing absorption of isoflavones in enterocytes. Micellization of isoflavone rich soy extract aims to improve bioavailability of their glycosidic chemical form. In this study we suggested a method to quantitate the phytochemicals absorbed and metabolized in the model organism Drosophila melanogaster and compared the bioavailability of glycosylated isoflavones and their respective aglycones in two formulations: powdered soy extract (SE) and its lecithin stabilised micelles (MSE). D. melanogaster were subjected to medium containing 3% or 10% of SE or MSE (~0.4 or 1.3 mg isoflavones/g medium) and non-absorbable dye for 24 h. Excreted dye was quantified via absorbance measurement at 630 nm to estimate isoflavone and total food consumption, while excreted isoflavones were measured with HPLC-DAD. According to our data, the addition of soy extract did not change consumption behaviour of female fruit flies compared to the standard food. We could confirm that micellization significantly improves bioavailability of soy extract and the amount of isoflavones that could be metabolized by the fruit fly. The differences in bioavailability were also observed between isoflavones: daidzin and genistin and their respective aglycones were absorbed and metabolized to ~60% in micellized form, while micellized glycitin and glycitein were absorbed and metabolized to nearly 90%. To conclude, we developed and validated a method to evaluate the bioavailability of phytochemicals in D. melanogaster and demonstrated that micellization improves absorption and metabolization of soy isoflavones.