Microwave-assisted extraction of bioactive compounds from bitter orange seed cotyledon and evaluating their antioxidant properties

In the present study, bioactive compounds were extracted from cotyledon of bitter orange (Citrus aurantium) seed, as a waste of citrus processing, using a microwave-assisted extraction method. The effects of four independent variables including microwave power (100-300 W), extraction time (5-15 min), sample weight (5-15 g), and solvent volume (100-200 mL) on responses of extraction yield, total phenolic content, total flavonoid content, free radical scavenging activity (IC50), ferric ion reducing antioxidant power (FRAP), cupric ion reducing antioxidant capacity (CUPRAC), and chelating capacity of extracts were investigated. Response surface methodology based on the central composite design was employed to investigate the effects of independent variables on the responses and also to optimize the extraction conditions. The optimum extraction condition included microwave power of 300 W, extraction time of 15 min, sample weight of 5 g, and solvent volume of 200 mL. Regarding the extraction yield, its amount increased significantly by increasing microwave power, extraction time, and sample weight, while it decreased significantly by increasing solvent volume. Also, the highest total phenolic content in the extract was observed at the lowest levels of microwave power and extraction time. Concerning the total flavonoid content in the extract, its amount increased significantly by increasing extraction time and solvent volume, while it decreased significantly by increasing sample weight. In addition, the CUPRAC of the extract increased significantly by increasing microwave power, extraction time, and solvent volume, as opposed to sample weight. In conclusion, microwave-assisted extraction can be suggested as a suitable method for extracting bioactive compounds from the bitter orange seed cotyledon.