Modeling the Influence of Extraction Parameters on the Recovery of Antioxidant Compounds of Microwave Extracted Citrus (Citrus reticulata) Peel by Response Surface Methodology

Background: Microwave-assisted extraction (MAE) is a green extraction technology that saves both in energy and time and that bioactive compounds can be extracted without loss as much as in traditional extraction methods. Objectives: This study aims to optimize the MAE process for maximizing the recovery of antioxidant compounds of flavonoids and the activity of radical scavenging of DPPH (2,2-diphenyl-1-picrylhydrazyl) from citrus peels (CP). Methods: The modeling used Box-Behnken Design (BBD) experimental design for optimizing three extraction parameters of time (5, 15, and 25 min), ethanol concentration (50%, 70%, and 90%), and extraction temperature (55, 65, and 75 °C). UHPLC-MS analysis was performed to identify the qualitative flavonoid content in the extract. Results: Our results showed that the optimum MAE conditions that maximize the total flavonoid content and antioxidant activity of the CP extract were extraction time of 16.87 min, 50% ethanol, and temperature at 75°C. The obtained CP extract had a TFC of 14.10 mg QE/g and antioxidant activity of 51.52%, which was in line with the predicted values. Flavonoids of neohesperidin, naringin, hesperidin, narirutin, and nobiletin were identified in the extract of CP. Conclusion: The ethanolic extract of CP was confirmed to have high flavonoids content with potent antioxidant activity.