Green and Efficient Simultaneous Enrichment and Separation of Multiple Valuable Bioactive Compounds from Agricultural Waste Ginkgo biloba Exocarp Using a Two-Phase Deep Eutectic Solvent System

To make full use of Ginkgo biloba exocarp, which was usually neglected as agricultural waste, a green and efficient protocol for simultaneous enrichment and separation of several bioactive compounds with different properties and applications from the exocarp was established for the first time. A two-phase deep eutectic solvent (DES) system was designed to enrich ginkgolic acids (GAs) to the hydrophobic phase and targeted procyanidine (PAC), flavonoids, and terpene trilactones (TTLs) to the hydrophilic phase by adjusting the polarity and hydrophilicity. The two-phase system developed with a hydrophobic DES MHL (l-menthol: 1-hexanol: lauric acid, 1:1.6:0.4) and a hydrophilic DES CCE (choline chloride: citric acid: ethylene glycol, 3:2:1) at a volume ratio of 1:1 gave the highest extraction yields. After extraction condition optimization, the extraction yield of GAs was 172.42 ± 1.66 mg/g in the MHL phase, and the extraction yields of PAC, flavonoids, and TTLs in the CCE phase were 3.10 ± 0.03, 9.95 ± 0.26, and 207.42 ± 4.50 mg/g, respectively. The results were significantly higher than those of traditional single-phase extraction systems with organic solvents. Afterward, the MHL extract solution of GAs could be utilized directly for the production of pesticides. The targets in the CCE extract solution were recovered for the preparation of G. biloba extract through the macroporous resin adsorption method. The recovery of PAC, flavonoids, and TTLs from the CCE phase was achieved by SP825 macroporous resin with recovery yields of 60.97, 75.97, and 83.79%, respectively. Therefore, this work not only provided a basis for improving the extraction efficiency by tailoring the polarity and hydrophobicity of the two-phase DES system, but also contributed to the exploitation and high-value utilization of waste G. biloba exocarp.