Ultrasound-assisted process for optimal recovery of phenolic compounds from watermelon (Citrullus lanatus) seed and peel

Ultrasound-assisted extraction (UAE) was optimized for the collection of phenolic compounds and determination of antioxidant activity of watermelon peel (WMP) and watermelon seed (WMS) using Box-Behnken design and response surface methodology. UAE process variables (sonication temperature, sonication time, and ethanol concentration) had a significant impact on the total phenolic content (TPC) and antiradical activity of WMP and WMS. The optimum conditions for WMP extraction (sonication temperature = 47.82 degrees C, sonication time = 31.63 min, and ethanol concentration = 42.84%) yielded maximum TPC (7.944 mg GAE/100 mL) and antiradical activity (85.150%) while UAE at 50.32 degrees C, 37.60 min, and 39.18% ethanol yielded maximum TPC (32.152 mg GAE/100 mL) and antiradical activity (85.947%) for WMS. The experimental values obtained matched well with the predicted values. Furthermore, of the nine phenolic acids studied, eight were identified and quantified by GC-MS analysis in WMS extracts while none were identified in WMP extracts.