Natural deep eutectic solvent as a green extraction medium for the ultrasonic-assisted extraction of sinapine thiocyanate from black mustard seeds

Herein, several choline chloride-based (ChCl) natural deep eutectic solvents (NADESs) were investigated for the ultrasonic-assisted extraction (UAE) of sinapine thiocyanate (ST) from black mustard seed (BMS). The NADES consisting of choline chloride and ethylene glycol (EG) was screened as the extraction solvent and single-factor experiments were carried out. In addition, compared with the conventional extraction solvents and extraction methods. The optimized extraction conditions were described below: NADES synthesized by ChCl and EG was used as an extractant with a water content of 20 %, and the solid–liquid ratio was 1:30 g∙mL−1. The mixture was extracted under the ultrasonic parameters of 60 ℃ and 200 W for 75 min. The extraction rate obtained using this method was higher than traditional solvents such as methanol, ethanol and water, and the time consumed was also greatly reduced compared to heated reflux extraction. A variety of instruments were used to characterize the experimental materials and further elucidate the extraction mechanism. Meanwhile, the antioxidant capacity of the ChCl/EG extract of BMS was determined by ultraviolet–visible spectrophotometry. The green evaluation of the method was carried out by the complex green analytical procedure index (ComplexGAPI). This work provides a green technique for valid extraction of ST from BMS, which is expected to be expanded to pharmaceutical, food and other related industries.