Green extraction of bioactive compounds from apple pomace by ultrasound assisted natural deep eutectic solvent extraction: Optimisation, comparison and bioactivity

Natural deep eutectic solvents (NADES) coupled with ultrasound assisted extraction (UAE) was evaluated as extraction techniques for bioactive compounds from apple pomace. Seven natural deep eutectic solvents (NADES) with different molar ratios were explored as green extraction solvents to evaluate extraction efficiency in terms of total flavonoid content (TFC), total phenolic content (TPC), lipid peroxidation inhibition (LBI) and antioxidant potential. The solvents which performed better than conventional solvent were DES1 (Choline chloride: glycerol (1:2)), DES2 (Choline chloride: lactic acid (1:3)) and DES5 ((Choline chloride: citric acid (1:1)). These solvents were further evaluated for optimisation of processing parameters in UAE-DES. The maximum TPC value was achieved using sonication time 40 min, water 30 %, solid/liquid ratio 1:30, temperature 40 °C, acoustic intensity 83.2 W/cm2 and duty cycle 75 %. HPLC of optimised extract was utilised for quantification of polyphenol compounds showing quercetin as main compound followed by chlorogenic acid, gallic acid, phloretin, phloridizin and rutin.