Deep eutectic solvents in the extraction of active compounds from Eucommia Ulmoides Oliv. leaves

Eucommia ulmoides Oliv. leaves (EULs) are a newly-developing food feedstock in China, containing various active compounds with important biological activities for humans. We evaluated the influence of deep eutectic solvents (DESs) with different hydrogen bond donors (HBD) on the yields of active compounds from EULs. As a result, EULs extracts obtained by DESs had the highest total phenolic content (Choline chloride-Levulinic acid, 73.39 mg GAE/g DW) and total flavonoid content (Choline chloride-Triethylene glycol, 147.29 mg RE/g DW), much higher than the samples obtained by water and 60% ethanol (w/w). In addition, DESs could effectively extract active compounds from EULs such as chlorogenic acid, rutin, geniposidic acid, and kaempferol. A correlation analysis revealed that lower pH increased the yields of total phenolics, chlorogenic acid, and salicylic acid. The polarity range of 49-50 kcal/mol was universally applicable to active compounds of EULs. Moreover, EULs extracts obtained by DESs exhibited excellent antioxidant activity in vitro. According to the multifactor analysis, the effects of HBD on the active compounds and antioxidant activity of EULs extracts were confirmed, and Choline chloride-Triethylene glycol was the most effective solvent for extracting active compounds from EULs. This study demonstrated the correlation between DESs with different HBD and the active compounds of EULs, providing a valid basis for the design and selection of tailor-made DESs to extract active compounds from EULs. [GRAPHICS] .