The extraction of bioactive compounds is generally carried out using organic solvents, although they are very harmful to the environment. The present study focuses on the extraction of bioactive compounds using natural deep eutectic solvents (NADESs), which are novel, green, and low-melting-point solvents. In this work, we seek to optimize the extraction process of total polyphenols from orange peel using four types of NADESs with different water concentrations, solid–liquid ratios, and extraction times. The results show that the best percentage of NADESs were as follows: 10, 30, and 50%; the solid–liquid ratio differs depending on the compound, and the optimal extraction time is generally estimated to be 30 min.

The aim of this study was to optimize and compare four different natural deep eutectic solvents (NADES) for the extraction of flavonoids in orange peels (Navel cultivar) from Valencia (Spain). Four NADES systems with two components were obtained in their corresponding molar ratios. Three independent variables were used for the optimization: solid-liquid ratio, extraction time and the percentage of NADES in water. The results showed the highest extraction was with choline chloride: fructose (NADES-1) with 50% water content, a solid–liquid ratio of 1:25 and extraction time of 23 min. The results demonstrate that the use of NADES is an efficient and ecofriendly alternative to extracted flavonoids from orange peels.