Extraction of phenolic compounds from Agrimonia eupatoria using microwave and ultrasound-assisted extraction methods

Agrimonia eupatoria (AE) is commonly used as a medicinal plant in Iran. In this study, microwave and ultrasound-assisted extraction (MAE and UAE) methods have been developed to extract phenolic compounds from AE. In addition, the impact of operational variables such as the solvent composition (ethanol and water), microwave and ultrasonic power, and extraction time on the content of total phenolic compounds (TPC) and antioxidant activity (AA) was evaluated through response surface methodology (RSM). The optimized conditions of MAE were as follows: microwave power was 200 W, extraction time was 15 min and ratio of ethanol to water was 0.78 v/v. Under these conditions, the maximum content of TPC and AA were 326.11 mg GAE/100g and 52.25% respectively. The maximum amount of TPC in UAE method was 355.12 mg GAE/100g. Antioxidant activity of about 75.92% was also achieved. The optimum extraction ultrasonic power, time and ratio of ethanol to water were defined as 100 W, 41.82 min and 1.17 v/v, respectively. High-performance liquid chromatography (HPLC) revealed the presence of five different types of phenolic compounds, namely chlorogenic acid, quercetin, rutin, cumaric acid and apigenin in the MAE and UAE extracts. The results indicated UAE was more efficient than the MAE to extract phenolic compounds from AE.