Simultaneous extraction of total polyphenols and triterpenes from leaves of Celtis sinensis by deep eutectic solvent hybrid system combined with response surface methodology

Abstract

Deep eutectic solvents (DES) have received extensive attention in the extraction of natural products in the last few years. They are considered a substitute for conventional organic solvents because of their environmental advantages. To efficiently extract bioactive polyphenols and triterpenoids from the medicinal plant Celtis sinensis, fifteen DESs were prepared. The resulting DES1 (choline chloride-levulinic acid) showed the maximum extraction yield of total polyphenols, while DES9 (choline chloride-1,2-propylene glycol) had the maximum yield of total triterpenes. Further, the extraction conditions of DES1 and DES9 were methodically optimized. After optimizing the extraction conditions of DES1 and DES9, the extraction yield of total polyphenols was enhanced from 82.05 mg g⁻¹ to 101.38 mg g⁻¹ and that of total triterpenes from 57.87 mg g⁻¹ to 72.72 mg g⁻¹, both significantly superior to those of traditional water- and methanol-based extraction approaches. We designed a new DES by mixing DES1 and DES9 in the ratio of 7.25 : 2.75 to perform extraction of both polyphenols and triterpenes with high efficiency. The new DES solvent simultaneously increased the extraction yields of polyphenols and triterpenes to 118.46 mg g⁻¹ and 88.51 mg g⁻¹, respectively, after response surface methodology. More importantly, the extract obtained by the mixed solvent of DES1 and DES9 displayed significant antioxidant activity superior to those of extracts individually produced by DES1 and DES9. Our results indicate that a DES-based approach has promising potential in extracting bioactive substances from medicinal arbor species with high efficiency and eco-friendliness.