Ultrasound-Assisted Extraction of Phenolics from Longan (Dimocarpus longan Lour.) Fruit Seed with Artificial Neural Network and Their Antioxidant Activity

Longan (Dimocarpus longan Lour.) is a non-climacteric subtropical fruit which is widely accepted by consumers all over the world for its pleasant flavor and health benefits. In the present work, the effects of ultrasonic power (120–300 W), temperature (30–70 °C) and ethanol concentration (40–80%) on the yield of total phenolics and 1,1- diphenyl-2- picrylhydrazyl (DPPH) radical scavenging activity were investigated with artificial neural network, and they were proved to be interactional and significant on the dependent variables. The R2 and MSE values of the models suggested good fitness and generalization of the artificial neural network. The results indicated a positive linear relationship between antioxidant activity and total phenolic content. Compared with conventional extraction, ultrasound-assisted extraction showed a higher yield of total phenolics and required a shorter extraction time. A stronger antioxidant activity of the ultrasonic extract was also found compared with conventional extraction.