Efficient removal of ginkgolic acids from Ginkgo biloba leaves crude extract by using hydrophobic deep eutectic solvents

Extract of Ginkgo biloba leaves (EGb) is a widely used phytotherapy drug, while ginkgolic acids (GAs) are considered as potentially hazardous constituents in EGb. In this work, a liquid-liquid microextraction method for removing ginkgolic acids from Ginkgo biloba leaves crude extract using hydrophobic deep eutectic solvent (DES) was reported. After screening and designing, a ternary hydrophobic DES composed of l-menthol, 1-hexanol and lauric acid at a molar ratio of 1:0.8:0.2, named as MHL, gave the highest removal rate of GAs. The removal conditions were optimized based on the removal rate of GAs, and the optimal conditions were 27.5 % (v/v) of ethanol solution used as the aqueous phase for dissolving the Ginkgo biloba leaves crude extract, 180 μL of the hydrophobic DES, removal temperature of 40 °C, and removal time of 24 min, respectively. Under these conditions, the removal rate of GAs in the model EGb solution reached 74.35 ± 1.56 %. Only one step removal could reduce the GAs content in the real Ginkgo biloba leaves crude extract to 4.02 μg/g (below 5.00 mg/kg). Scaling up the removal operation volume by 100 times, the removal rate of GAs did not decrease, but even improved. The retention rates of total flavonoids and ginkgolides always kept at high levels. This work provides the basic for further considering hydrophobic DESs as green media for efficiently removing the GAs in the standardized EGb production.