Two-phase systems developed with hydrophilic deep eutectic solvents (DESs) and hydrophobic DESs were prepared in this study for the first time. Ginkgo biloba leaves containing several bioactive compounds were chosen as the model plant material to evaluate the possibility of the two-phase DES system as a designer solvent for the simultaneous extraction of the various bioactive compounds with different polarities. After tailoring, a two-phase DES system prepared with two hydrophilic DESs and one hydrophobic DES at a volume ratio of 35 : 5 : 40 could effectively extract flavonoids, terpene trilactones (TTLs), procyanidine (PAC) and polyprenyl acetates (PPAs) simultaneously from the Ginkgo biloba leaves. The extraction conditions were further optimized using the response surface methodology. When the two-phase DES system was employed in the extraction under the optimal conditions, the PPAs moved into the hydrophobic phase, and the flavonoids, TTLs, and PAC were enriched into the hydrophilic phase. The first extraction rates for PAC, flavonoids, TTLs and PPAs were 86.07%, 77.72%, 93.29% and 94.63%, respectively. After extraction, the hydrophilic and hydrophobic phases containing different bioactive compounds could be easily separated for different preparations. Extraction with the two-phase DES system is a new application trial of DESs, which has the potential to be widely used for the extraction of bioactive compounds from plant materials or removal of different polar impurities from specific extracts.

DESs can readily dissolve water-insoluble drugs to a high concentration and enhance the stability of dissolving drugs ( e.g. aspirin).

The instability of dietary flavonoids is currently a challenge for their incorporation in functional foods.