Phenolic compounds from date pits: ultrasonic-assisted extraction, antioxidant activity and component identification

Ultrasonic and response surface methodology were used to extract phenolic compounds from date pits and optimize extraction parameters including ultrasonic time, solid to liquid ratio and ethanol concentration. A mathematical model of the three parameters for a high extraction yield was established. The results showed that all the extraction parameters and the interaction between solid to liquid ratio and ethanol concentration significantly affected the extraction yield. The optimized extraction parameters were ultrasonic time of 42 min, solid to liquid ratio of 1:46 g/mL, and ethanol concentration of 60%, under which the extraction yield was 8.26%. In vitro antioxidant activity and components of the phenolic compounds was investigated by the antioxidant tests and HPLC, respectively. The antioxidant assays of DPPH and ABTS free radicals, reducing power and total antioxidant capacity suggested that the phenolic compounds from date pits had a high antioxidant activity, and the HPLC analyses revealed that the extracts were mainly composed of seven phenolics.