Optimization and GC-MS Analysis of Extracting Pepper Leaves Essential Oil by Ultrasonic Assisted Distillation Based on Deep Eutectic Solvents

The optimization of the essential oil extracted from pepper leaves by deep eutectic solvents was carried out using one-factor-at-a-time method and response surface methodology. Using a Box-Behnken design,a mathematical model was established to investigate the effects of solvent-solid ratio,ultrasonic power and extraction time on the yield of essential oil,respectively. The results showed that the most suitable deep eutectic solvent was choline chloride/urea. The optimum conditions of pepper leaves essential oil were as follows:The solvent-solid ratio was 14:1 mL/g,the ultrasonic power was 300 W,the extraction time was 53 min. Under the optimal conditions,the yield of essential oil of pepper leaves was 1.380%±0.018%,which was better than steam distillation and ultrasonic-assisted steam distillation. The yield of pepper essential oil increased by 14.33% and 5.18%,respectively. A total of 34 compounds were identified by GC-MS. The main components of essential oil were δ-elemene(19.75%),α-cubebene(9.17%),caryophyllene(8.97%),α-gurjunene(6.12%),β-eiemene(5.13%).The method for extracting pepper leaves essential oil by using choline chloride-urea as deep eutectic solvent is feasible.