Extraction of phenolic compounds from lime peel waste using ultrasonic-assisted and microwave-assisted extractions

Microwave-assisted extraction (MAE) and ultrasonic-assisted extraction (UAE) have been studied to extract natural phenolic compounds from lime peel wastes. A response surface methodology with a three-level and three-factor Box-Behnken design was used to predict the optimal conditions of each extraction parameter based on the total phenolic contents, antioxidant activities and the half maximal inhibitory concentration. The results showed that the optimal predicted MAE was obtained at 55% ethanol concentration, 140 W microwave power for 45 s with 8 repeats of the extraction step. Meanwhile, the optimal predicted UAE was at 55% ethanol concentration, 38% amplitude and 4 min extraction time. UAE was the more effective method to extract the total phenolics (54.4 mg GAE/g) with high antioxidant activity and saving of time of 33% compared with MAE. Therefore, the natural phenolic extract from lime peel waste might be available as a source of active and functional compounds for pharmaceutical and food products.