Efficient extraction, excellent activity, and microencapsulation of flavonoids from Moringa oleifera leaves extracted by deep eutectic solvent

A deep eutectic solvent (choline chloride (ChCl)-urea) was chosen to extract flavonoids from Moringa oleifera leaves (F MO L), the condition of extraction was tailor-made, under the optimal extraction conditions (material-to-liquid ratio of 1:60 g/mL, extraction time of 80 min, extraction temperature of 80 °C), the highest extraction efficiency reached 63.2 ± 0.3 mg R/g DW, and nine flavonoids were identified. Then, the biological activities including antioxidant activities, antibacterial activities, and anti-tumor activities were systematically studied. F MO L was superior to positive drugs in terms of antioxidant activity. As to DPPH investigation, the IC 50 of F MO L and Vc were 64.1 ± 0.7 and 176.1 ± 2.0 µ g/mL; for the ABTS, the IC 50 of F MO L and Vc were 9.5 ± 0.3 and 38.2 ± 1.2 µ g/mL, the FRAP value of F MO L and Vc were 15.5 ± 0.6 and 10.2 ± 0.4 mg TE/g, and ORAC value of F MO L and Vc were 4687.2 ± 102.8 and 3881.6 ± 98.6 µ mol TE/g. The bacteriostatic (MICs were ≤ 1.25 mg/mL) activities of F MO L were much better than propyl p-hydroxybenzoate. Meanwhile, F MO L had comparable inhibitory activity with genistein on tumor cells, IC50 was 307.8 µ g/mL, and could effectively induce apoptosis in HCT116. Microcapsules were prepared with xylose-modified soybean protein isolate and gelatin as wall materials; after that, the intestinal release of modified F MO L microcapsules was 86 times of free F MO L. Therefore, this study confirmed that F MO L extracted with ChCl/urea has rich bioactive components, and microencapsulated F MO L has potential application in food industry. Graphical abstract