Extraction of phenolic compounds from melissa using microwave and ultrasound

In this study, extraction of phenolic compounds from melissa by microwave and ultrasound was studied. In both the microwave and ultrasound extractions, the effects of extraction time (5-20 min for microwave; 5-30 min for ultrasound) and solid-to-solvent ratio (1:10, 1:20, and 1:30 g mL-1) on total phenolic content (TPC) were investigated. Effects of different powers (50% and 80%) were also studied for the ultrasound extraction. As a solvent, water was used. In microwave extractions, the highest TPC of extracts (145.8 mg GAE g-1 dry material) was obtained in 5 min and at a 1:30 solid-to-solvent ratio. For ultrasound extraction, the conditions that gave the highest TPC (105.5 mg GAE g-1 dry material) were 20 min with a 1:30 solid-to-solvent ratio at 50% power. Extracts obtained at the optimum conditions of microwave and ultrasound were compared with conventional extraction and maceration, respectively. TPC and antioxidant activity of the extract was the highest in microwave extraction among all extraction methods. In addition, microwave reduced extraction time by 83%.