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

Unlabelled: A deep eutectic solvent (choline chloride (ChCl)-urea) was chosen to extract flavonoids from leaves (FL), 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. FL was superior to positive drugs in terms of antioxidant activity. As to DPPH investigation, the IC of FL and Vc were 64.1 ± 0.7 and 176.1 ± 2.0 g/mL; for the ABTS, the IC of FL and Vc were 9.5 ± 0.3 and 38.2 ± 1.2 g/mL, the FRAP value of FL and Vc were 15.5 ± 0.6 and 10.2 ± 0.4 mg TE/g, and ORAC value of FL and Vc were 4687.2 ± 102.8 and 3881.6 ± 98.6 mol TE/g. The bacteriostatic (MICs were ≤ 1.25 mg/mL) activities of FL were much better than propyl p-hydroxybenzoate. Meanwhile, FL had comparable inhibitory activity with genistein on tumor cells, IC50 was 307.8 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 FL microcapsules was 86 times of free FL. Therefore, this study confirmed that FL extracted with ChCl/urea has rich bioactive components, and microencapsulated FL has potential application in food industry.

Supplementary Information: The online version contains supplementary material available at 10.1007/s13399-023-03877-8.