Ultrasound-assisted deep eutectic solvent extraction and bioactivity evaluation of phenolic compounds from white birch bark

White birch bark, a byproduct of the construction and paper industries, is an underexploited resource rich in bioactive phenolic compounds. Despite the well-documented pharmacological properties of terpenoids in birch bark, phenolic compounds remain insufficiently studied, particularly regarding efficient extraction methods. Deep eutectic solvents (DESs) are eutectic mixtures formed through hydrogen bonding and other interactions between two or more components, demonstrating great potential in the extraction of active ingredients. Hence, this study optimized the ultrasound-assisted (UA) combined with DESs extraction (UADESs) of total phenols (TTP) from white birch bark. The results showed that the optimum DESs was a mixture of choline chloride and glycolic acid (molar ratio 1:2) with 10 % water. The optimal UADESs conditions (extraction temperature 56.05°C, extraction time 16.01 min, ultrasonic power 423.5 W, material-liquid ratio 1:51.49 g/ mL) yielded 29.17 mg/g TTP, surpassing traditional ethanol and ultrasonic methods by 2.27 and 1.38-fold, respectively. UPLC-MS/MS identified 14 phenolic compounds. The extracts by UADESs exhibited superior antioxidant, antimicrobial, and hypoglycemic activities. These findings highlight the potential of UADESs for valorizing birch bark waste into high-value bioactive compounds, providing an environmentally friendly approach for applications in the pharmaceutical and food industries. • Birch bark, an industrial byproduct, is a rich source of bioactive compounds. • DESs-based extraction enhanced phenol yield by up to 2.27 and 1.38 fold compared to conventional methods. • The extracts showed potent antioxidant, antimicrobial, and hypoglycemic activities. • Low-toxicity DESs extraction offers an eco-friendly alternative to traditional organic solvents.