Urea-Glycerol Based Natural Deep Eutectic Solvent on Microwave Assisted Extraction of Essential Oil of Cymbopogon Citratus

Abstract

Urea in combination with glycerol was applied in the process intensification of Urea Glycerol Microwave-Assisted Extraction (UG-MAE) of the essential oil of Cymbopogon citratus. The objective of this research was to evaluate the effect of urea-glycerol molar ratio and leaf length on the UG-MAE of the essential oil of Cymbopogon citratus. This work also proposed and validated a kinetics model based on the diffusion-control assumption. The UG-MAE for Cymbopogon citratus was carried out in a microwave extractor by altering the molar ratio of urea and glycerol and the leaf length. The research findings indicated that urea-glycerol functions effectively as a deep eutectic solvent for extracting the essential oil of C. citratus. It was observed that the solubilization rate of essential oil was greater in shorter leaves of C. citratus compared to longer leaves. In comparison, the solubilization rate for an equal molar ratio of urea-glycerol was lower than that with a higher ratio of urea to glycerol. Optimal conditions for the UG-MAE process were identified and reported in this study. Gas chromatography analysis indicated that Z-citral, E-citral, and trans-caryophyllene are the three primary components present in the essential oil of Cymbopogon citratus obtained through the UG-MAE process. The proposed diffusion-controlled slab particle model was validated, demonstrating a good fit for the experimental data. The kinetics parameters obtained for the UG-MAE of Cymbopogon citratus included the Henry constant, which varied between 0.24 and 0.30, and the effective diffusivity, which ranged from 5.08.E-07 to 3.93.E-06 cm2/s. The concentration profile of the essential oil, expressed as the ratio of oil concentration to the initial oil concentration concerning axial position and time in the solid particle, provides greater insight into the UG-MAE behavior related to Cymbopogon citratus.