Eco-friendly extraction of anthocyanins compounds from red radicchio by-products with natural deep eutectic solvents

The food industry requires novel green solvents to extract bioactive compounds, particularly regarding agrifood by-product valorization. Considering this, an eco-friendly ultrasound-assisted method for extracting phenolic compounds from the processing residues of red chicory of Treviso Precoce IGP using natural deep eutectic solvents (NaDESs) has been developed. Citric acid:choline chloride (1:2) was identified as the most suitable NaDES based on its stability and extraction capability towards phenolic compounds. Using a three-factor, three-level Box–Behnken experimental design combined with Response Surface Modeling, the maximization of polyphenol yield by optimizing the water percentage in NaDES, the ultrasound extraction time, and the citric acid: choline chloride molar ratio has been obtained. The maximum extraction yield (117.43 ± 0.33 and 2894 ± 0.22 μg/mL of chlorogenic and chicoric acids, respectively) was obtained by using a 3:2 citric acid:choline chloride molar ratio with 25% of water and by sonicating the extracts for 49 min. Considering the green nature, biodegradability, and low cost of NaDES, the obtained polyphenolic extracts are expected to offer advantages in industrial food and pharmaceutical applications, eliminating the need for expensive downstream purification steps.