Microwave-assisted deep eutectic solvent extraction and quantification of six bioactive compounds from Vaccinium vitis-idaea L. Leaves

Vaccinium vitis-idaea L. leaves (VVLL), a renewable forest resource abundant in active compounds, have not been well utilized. This study employed microwave-assisted natural deep eutectic solvents (NADES) to efficiently extract the total flavonoids from VVLL. Among various combinations, the choline chloride-lactic acid solvent exhibited great selectivity for flavonoids, with the highest extraction rate of 269.99 ± 1.42 mg/g, ( n  = 3). Six flavonoids in the VVLL extract were further analyzed by UPLC-MS/MS and HPLC. They included two isomers, a triterpenic acid, and Asiatic acid which is firstly reported in VVLL. The total flavonoid content extracted by our method is 3.4 times higher than that of Vaccinium vitis-idaea L. fruit. Fourier-transform infrared spectroscopy results revealed NADES-flavonoid hydrogen bonding as the driving mechanism for enhanced extractability. The extracted flavonoids exhibited superior antioxidant capacity against DPPH and ABTS radicals in comparison to the traditional alcohol extraction methods. Specifically, the scavenging activities were also significantly improved. In conclusion, as a high-quality source of flavonoids, VVLL has substantial promise for the development of novel flavonoid products.