Abstract:Essential oils were extracted from pepper leaves by microwave-assisted distillation using different types of deep eutectic solvents as solvents. Different types of eutectic solvents were compared, and the main factors affecting the yield of essential oils (solvent-solid ratio, microwave power, extraction time) were optimized by single factor test and response surface methodology. The results showed that the choline chloride-urea deep eutectic solvent was the best extractant, when the conditions was as follow: solvent-solid ratio of 16:1 (mL/g), the microwave power of 480 W, and the extraction time of 53 min. Under these conditions, the maximum yield of essential oil was 1.42%. The comparison test indicated that the yield of the essential oil was significantly better than that of steam distillation and microwave-assisted distillation, which increased by 17.48% and 5.66%, respectively. The chemical constituents of the essential oils were identified by gas chromatography-mass spectrometry (GC-MS). A total of 34 substances, the main components were isospathulenol (25.47%), δ-elemene (17.52%), caryophyllene (8.27%), α-cubebene (7.07%), α- gurjunene (5.59%), (+)-ledene (5.02%). A method for extracting pepper leaves essential oil by using choline chloride-urea as deep eutectic solvent could be feasible.
