Esen Bilge Biçer, Şeniz Karabıyıklı Çiçek, Ebru Yabaş
Propolis is a resinous substance produced by honey bees (Apis mellifera) and is rich in biologically active compounds. Efficient extraction of these compounds depends largely on solvent selection and the optimization of extraction conditions. In this study, ultrasonic-assisted extraction (UAE) conditions from crude propolis were optimized using two solvents (dimethyl sulfoxide (DMSO) and ethanol) through a Box–Behnken experimental design based on response surface methodology (RSM). Response surface methodology (RSM) was employed to evaluate the effects of solvent concentration (0-100%), extraction temperature (30–50 °C), and extraction time (30-180 min) on extraction yield. The DMSO-based UAE model showed high statistical significance with an R² value of 0.9950 (F = 154.15, p <0.0001). The optimal extraction conditions were determined as 98.34% solvent concentration, 42.20°C extraction temperature, and 142.60 min extraction time, resulting in a yield of 54.17%. Similarly, the ethanol-based UAE model was also significant (F = 113.09, p <0.0001; R² = 0.9932), with optimal conditions of 99.19% solvent concentration, 45.26 °C extraction temperature, and 171.5 min extraction time, yielding 55.82%. In both solvent systems, solvent concentration was identified as the most influential parameter affecting extraction yield (p <0.0001). Bioactivity analyses revealed that DMSO extracts contained higher TPC (325.27 ± 0,05 mg GAE/g) and exhibited stronger antioxidant activity (DPPH SC50: 11.90 ± 1.6 µg/mL; ABTS SC50: 147.7 ± 0.4 µg/mL) compared with ethanol extracts. Conversely, ethanol extracts demonstrated stronger antimicrobial activity against Escherichia coli, Salmonella enterica serovar Typhimurium, Bacillus cereus, and Staphylococcus aureus, with consistent MIC values of 25 µg/mL. Overall, the findings indicate that both solvents provide high extraction efficiencies (~54-56%) under optimized UAE conditions. Furthermore, solvent selection plays a decisive role in determining the bioactivity profile. The results show that using DMSO in extraction is suitable for maximizing antioxidant properties, while using ethanol is more suitable for antimicrobial applications.