Optimization of Propolis Extraction Under Thermosonication and Quantification of Bioactive Compounds by LC-MS/MS

Thermosonication is a treatment that combines ultrasound power and mild temperatures. In this study, thermosonication was used to identify a new optimized model to maximize phenolic content, antioxidant capacity, and balsam yield of extract. A central composite design was employed to investigate the effects of ethanol concentration (50–100%), temperature (30–70 °C), time (10–50 min), and solid solvent ratio (1:100–1:300 g/mL). The effectiveness of the optimized method was compared to conventional solid-liquid extraction methods that carried out following condition: 75% ethanol concentration, 50 °C, and 1:200 g/mL solid solvent ratio during 24 h. Under optimal conditions (90% ethanol, 51 °C, 32 min, and 1:300 g/mL solid solvent ratio), total phenolic content (252.74 mg GAE/g), flavonoid content (222.32 mg CE/g), antioxidant activity (1.43 mmol TEAC/g), and (71.99%) were greater than the conventional extraction. The quality of propolis extract varies greatly depending on the source, extraction parameters, and processing procedures. Therefore, balsam yield, which represents the soluble fraction of propolis, might be considered as a crucial quality measurement. Thirteen bioactive compounds were quantified by LC-MS/MS. Ferulic acid (5.31–6.55 mg/g propolis) was found major phenolic acid while quercetin (0.14–0.15 mg/g propolis) was the major flavonoid. Also, taxifolin was identified for the first time in propolis. In addition, close R2 and adj-R2 values and the results of validation study demonstrated that the new model was fitted well and highly efficient method to produce high-quality propolis extract.