Extraction and Analysis of Phenolic Compounds from Rocket: Development of a Green and Innovative DES-Based Extraction Method

<i>Eruca sativa</i> Mill. is an annual plant belonging to the Cruciferous family that is characterized by the presence of antioxidant bioactive molecules such as phenolic compounds. Their extraction is usually performed through solid-liquid extraction based on the use of organic solvent. Deep eutectic solvents (DESs) are new green solvents capable of increasing bioactive molecules yield if replaced with organic solvents. The aim of this work was to develop a green analytical method based on the use of DESs for the determination of phenolic compounds in rocket plants. The extraction optimization involved the selection of the best extraction solvent among different selected DESs and the study of the parameters that mainly affect the extraction yield: the quantity of water to add to the selected DES to reduce its viscosity, the matrix-to-solvent ratio, and the time and temperature of the extraction. ChCl-glucose (1:2 molar ratio) DES was selected as the extraction solvent under the following optimized conditions: 1:50 (<i>w</i>/<i>v</i>) as the matrix-to-solvent ratio; 30% of water was added to the DES; extraction time of 30 min; and extraction temperature of 50 °C. The rocket phenolic compounds profile was determined through a high-performance liquid chromatography coupled with mass spectrometry (HPLC-MS) analysis. The innovative green method was applied to real plant samples to determine the growth conditions that favored the accumulation of bioactive molecules.