Optimizing the ultrasonic isolation of phytochemicals from Satureja hortensis L.: Response surface methodology approach, chemical profile, and thermal behavior of optimized extract

Summer savory ( Satureja hortensis L.) was sonicated to obtain extracts rich in highly desirable phytochemicals. Despite this, the plant is still not investigated thoroughly. Therefore, this study aimed to use and optimize ultrasound-assisted extraction for isolation of bioactive compounds for summer savory, and to study chemical profile and thermal properties of the extract obtained under optimal conditions. The box-Behnken experimental design with 17 experiments was created for process optimization in combination with response surface methodology. Investigated responses were total phenolic (TPC) and flavonoid (TFC) contents and two antioxidant assays, DPPH (IC 50 ) and ABTS (EC 50 ) assays. Independent variables were ethanol concentration (40–80 %), temperature (40–80 °C), and liquid-solid ratio (20–40 mL/g). Experimentally obtained results were adapted to the polynomial model with multiple regression using analysis of variance to evaluate the obtained model and assess optimal values for both independent and dependent variables. Predicted values for extraction parameters were ethanol concentration of 40 %, temperature 80 °C, and LSR 31.3 mL/g. Estimated values were 135.55 mg GAE/g, 23.97 mg RU/g, 27.66 µg/mL, and 29.62 µg/mL for TPC, TFC, IC 50 , and EC 50 , respectively. UHPLC-DAD-MS/MS analysis showed that the dominant compound in the investigated extract was rosmarinic acid (52.25 µg/mL), followed by chlorogenic acid (1.82 µg/mL). The analyzed sample showed a glass transition at 50 °C and thermal degradation onset at 245 °C. Decomposition occurred in five stages between room temperature and 800 °C, with major mass losses due to organic compounds’ degradation and polymerization, leaving a 38.3 % residue. • Summer savory extracts were prepared using ultrasound-assisted extraction technique. • Optimization was performed with response surface methodology and Box-Behnken design. • Investigated parameters were total phenolic and total flavonoids contents, DPPH, and ABTS assays. • Extract obtained under optimal conditions was analyzed for presence of polyphenolic compounds. • Thermal analysis indicated complex nature of the optimized extract with five-stage decomposition.