Optimization of ultrasonic-microwave assisted extraction of polyphenols from jackfruit peel and evaluation of its antioxidant activities

In order to maximize the yield of polyphenols from jackfruit peel,response surface methodology(RSM)was employed to optimize the ultrasonic-microwave assisted extraction(UMAE) conditions,and the antioxidant activities of the polyphenol extracts were evaluated in vitro. On the basis of single-factor experiments,the Box-Behnken center-composite experimental design principle was used to design the experiments and the response surface analysis with 4 factors and 3 levels was adopted. A second order quadratic equation for extraction of polyphenols was created. After analyzed the significance of various factors and their interactions,the optimal extraction conditions for polyphenols from jackfruit peel were determined as follows:70% aqueous ethanol as the extraction solvent,1∶40 as solid-liquid ratio,extraction time 12 min and microwave power 75 W.The extraction yield of polyphenols was determined to be 7.19 mg/g under the optimized extraction conditions,which were above that of traditional hot water extraction,microwave assisted extraction and ultrasonic assisted extraction(1.04 mg/g,5.23mg/g and 5.89 mg/g,respectively). These results confirmed that UMAE of polyphenols had great potential and efficiency compared with traditonal extraction technologies. Furthermore,the experiments of antioxidant activity showed that polyphenol extracts of jackfruit peel exhibited strong antioxidant activities by the DPPH and ABTS radical scavenging assays,and the EC50 were 101.39 μg/m L and 106.60 μg/m L,respectively.The present study showed that the jackfruit peel were strong radical scavengers and could be considered as a good source of natural antioxidants for medicinal and commercial uses.