Three-stage microwave extraction of cumin (Cuminum cyminum L.) Seed essential oil with natural deep eutectic solvents

As a class of promising green media, natural deep eutectic solvents (NADESs) have attracted more and more attention in recent years. In this paper, a novel method based on microwave-assisted natural deep eutectic solvents pretreatment coupled with microwave hydrodistillation (MA-NADES-MHD) was used for the extraction of essential oil from Cuminum cyminum L. seed. NADESs were used as pretreatment solvents for adsorbing microwaves and dissolving cellulose. The maximum yield of essential oil obtained with this three-stage microwave extraction technology was 2.22% (w/w) when the natural deep eutectic solvent composed of choline chloride and L-lactic acid (with 1:3 of molar ratio) with 40% (w/w) of water. Compared with microwave hydrodistillation (MHD) and ultrasound-assisted natural deep eutectic solvents pretreatment combined with microwave hydrodistillation (UA-NADES-MHD) in which essential oil yield of 1.13% (w/w) and 1.57% (w/w) were obtained, respectively, the MA-NADES-MHD naturally brought more essential oil. Notably, a total of 45, 48, and 58 volatile components were identified by using gas chromatography-mass spectrometry with MHD, UA-NADES-MHD, and MA-NADES-MHD, respectively. Hence, NADESs had a significant impact on the extraction of essential oil with higher yield, premium quality, and more quantity, especially when it was combined with microwave technology. Moreover, the MA-NADES-MHD as an economical and eco-friendly technique had the potential to be applied to other plant materials.