Ultrasound-assisted deep eutectic solvent extraction of kukoamine A and kukoamine B from Lycii cortex

Abstract

Deep eutectic solvents (DES), are new environmentally friendly and efficient extraction solvents, and have considerable importance for environmental protection and sustainable development. In this study, ultrasound-assisted extraction (UAE) using DES was carried out to extract kukoamine A (KuA) and kukoamine B (KuB) from Lycii cortex (LyC). The DES was synthesised using a magnetic stirring method. A novel approach to extract KuA and KuB from LyC was developed by combining UAE with DES. Different DES formulations were tested to evaluate the efficiency of KuA and KuB extraction. Among them, choline chloride-lactic acid (ChCl-LA) DES had the best effect, and its extraction rate was much higher than that of methanol, which was 8.5 times that of methanol. Both single factorial experiments and response surface methodology (RSM) were used to optimise and model the extraction process. Density functional theory was also used to discuss the extraction mechanism. It was found that HBD and HBA will interact with hydrogen bonding and van der Waals interactions during the formation of DES, and these interactions will also affect the decrease in electron density. Taking ChCl-LA and ChCl-urea as examples, it was found that the binding energy of ChCl-LA was lower than that of ChCl-urea, indicating that ChCl-LA had a stronger interaction with the target substance and a higher extraction rate. The combination of UAE-DES proved to be a sustainable, effective, and simple extraction technique for the recovery of KuA and KuB from LyC.