Optimized ultrasound-assisted extraction of betulin from Betula pendula bark: a sustainable approach to forest residue valorization

Abstract The outer bark of Betula pendula (silver birch), a lignocellulosic byproduct of wood processing, offers valuable opportunities for the recovery of high-value bioactive compounds. betulin, a triterpenoid responsible for the white coloration of silver birch bark, has attracted considerable attention due to its pharmacological properties, including antioxidant, anti-inflammatory, and anticancer effects. In this study, a green ultrasound-assisted extraction (UAE) method was developed and optimized for the selective extraction of betulin from Betula pendula outer bark. In order to evaluate the effects of ethanol concentration, temperature, sonication amplitude, and cycle on betulin yield, a Box–Behnken design was employed in combination with response surface methodology. Optimal conditions were identified at 92% ethanol, 57 °C, 70% amplitude, and 0.3 Hz − 1 cycle for 15 min of extraction. The process demonstrated excellent repeatability (C.V. < 5%). A positive correlation was identified between betulin concentration and antioxidant capacity, thereby confirming the efficacy of the employed methodology. This work constitutes a significant UAE protocol for B. pendula outer bark, delivering 34.63 mg·g − 1 betulin and outperforming conventional techniques in terms of time and solvent usage, thus contributing to the development of circular biorefinery approaches within the wood industry.