Extraction of phenolic compounds from rosemary using choline chloride - based Deep Eutectic Solvents

Deep eutectic solvents (DES) have been explored as an alternative to hazardous solvents to extract natural bioactive compounds. In this work, choline chloride-based DES (neat and hydrated) were assessed in the extraction of phenolics from rosemary leaves. The DES studied on an initial screening showed a total phenolic content (TPC) up to 220% higher than the control. The solubilities of the main rosemary biocompounds, estimated by COSMO-RS, showed a positive correlation to TPC. Choline chloride:1,2-propanediol (CPH) was selected for further optimization. At the optimal conditions (65 degrees C, liquid: solid ratio of 40:1 and 50 %wt of water), the antioxidant activity and TPC were 80 mg of Trolox equivalent/g and 78 mg of gallic acid equivalent/g, respectively. The antimicrobial activity of the optimized extract revealed inhibition of 39-51% to all bacteria tested. In summary, an extract with good antioxidant and antimicrobial activities was obtained from rosemary leaves using CPH as solvent.