Optimization of microwave assisted extraction of bioactive compounds in oregano and lovage ethanolic extracts

Oregano and lovage contain a wide variety of bioactive compounds, but conventional extraction techniques usually generate small amounts of secondary metabolites. Thus, the extraction method and the recovery of these compounds represent a current challenge. The aim of this study was to optimize 3 microwave-assisted extraction (MAE) parameters, by response surface methodology (RSM), to obtain ethanolic bioactive extracts from oregano and lovage. The obtained extracts were assessed for their total phenolic content (TPC), antioxidant activity (AA), radical scavenging activity (I%), and antibacterial activity, by determining the minimal inhibitory concentration (MIC) against Escherichia coli and Staphylococcus aureus. The ethanol concentration (X₁: 40, 60 and 80%), microwave power (X₂: 160; 480 and 800 W), and repetitions (X₃: 1 to 10 times) were set as independent variables. The obtained models were validated with new experimental results, and confirmed for the 3 response parameters: TPC, AA, and I%. High-performance liquid chromatography (HPLC) was used to identify and quantify the main phenolic compounds in both optimum oregano and lovage extracts. The optimal extraction parameters were obtained with 49% ethanol, 160 W and 10 repetitions for oregano, whereas for lovage, 53% ethanol, 800 W power, and 10 extraction repetitions were optimal.