Optimizing ultrasound-assisted extraction for enhanced yield of bioactive compounds from Vaccinum myrtillus and Rubus idaeus bioresidues

Due to the high nutritional value of berries, their extensive production has led to the accumulation of bioresidues. To leverage these residues, the distinct chemical composition, and functional properties of the leaves and other aerial parts can be used to produce high-value ingredients for cosmetics. Ultrasound-assisted extraction (UAE) is considered simple, fast, efficient, and more affordable than other techniques for obtaining bioactive extracts. This study aimed to determine the optimal conditions for maximizing ultrasound-assisted extraction yields from raspberry (RB) and blueberry (BB) pruning using response surface methodology (RSM). Three factors were analyzed: the ethanol-to-water solvent ratio (ranging from 0 % to 100 % ethanol), extraction time (ranging from 5 to 30 min), and extraction power (ranging from 20 % to 100 %, with a maximum ultrasound power of 500 W). The Box-Behnken design included 17 individual randomized runs to optimize the extract's dry weight range from 22.2 to 202.8 mg/g for RB and 123.5–394.0 mg/g for BB. The optimal extraction point for RB was at 40 % ethanol-to-water ratio, 16 min, and 98 % extraction power, while for BB, it was at 59 % ethanol in water, 30 min, and 73 % extraction power. Higher levels of hydrolyzable tannins characterized the optimal point of RB, while BB showed greater contents of flavonoids. Both revealed strong antioxidant and antibacterial activities, with RB showing higher antioxidant activity than Trolox. These results suggest that the extracts from pruning are obtained at interesting compositions and yields, offering advantages to use in the cosmetic industry due to their bioactivity.