Recyclable menthol-based deep eutectic solvent micellar system for extracting phytochemicals from Ginkgo biloba leaves

With an emphasis on human health, the demand for natural products is progressively increasing and sustainable extraction technologies for phytochemicals are receiving greater attention. In the present study, we established a naturally recyclable two-phase aqueous micellar system comprising menthol-based hydrophobic deep eutectic solvent (DES) in water. Typical representative phytochemicals from Ginkgo biloba leaves included flavonoid glycosides, terpene lactones, and bioflavonoids. These compounds have differing polarities and were selected as targets for the evaluation of our novel menthol-based aqueous DES as a green and sustainable extraction technology for partitioning various compounds. Components of the aqueous DES system and extraction process were systematically studied, and the following optimal conditions were identified: menthol–acetic acid ratio of 1:1 (mol/mol), DES–water ratio of 1:1 (v/v), solid–liquid ratio of 15:1 (mg/mL), extraction power of 200 W, and extraction time of 10 min. The two-phase system easily separated compounds with differing polarity into the upper (DES-rich phase) and lower (water phase) phases after extraction. Analyses of the related mechanisms indicated that micelle formation of menthol-based DES in water was the dominant separating process and that this process provided large contact areas between target compounds and extraction solvent, thereby promoting extraction from G. biloba leaves. Moreover, this aqueous DES system could efficiently be recovered and reused in regeneration studies. This novel menthol-based aqueous DES system provides a sustainable extraction technology for various phytochemicals from plant materials.