Extraction of Bioactive Compounds from Celery Root Peels Using an Ultrasound-Assisted Method with Choline Chloride–Based Deep Eutectic Solvents

The concepts of sustainable and green technology have come to the forefront due to problems such as increasing environmental pollution, depletion of resources, and uncontrolled increases in industrialization. Green chemistry aims to reduce or completely eliminate pollution in the environment. In this study, both the ultrasonic method, which is a form of green technology, and deep eutectic solvents, which are among green solvents, were used, and a perspective on creating economic value from a waste product (celery root peel) is presented. In this context, phytochemical compounds (total flavonoid content and antioxidant activities) were obtained from celery root peels by ultrasonic-assisted extraction using 10 different choline chloride–based deep eutectic solvents, and the results were compared with methanol, an organic solvent. As a result, according to the total flavonoid content, the most effective deep eutectic solvent was choline chloride to sucrose, while according to the antioxidant activity value, choline chloride to lactic acid was found to be effective. For all of the analyzed bioactive compounds, higher or equal yields were obtained with all deep eutectic solvent extracts compared to methanol, and deep eutectic solvents could be alternatives to organic solvents (such as methanol) that may have toxic effects on humans or the environment.