Optimization of extraction process of polyphenols from fruit shell of Metaplexis japonica (Thunb.) Makino and evaluation of its antioxidant activity

Objective: To determine the optimum extraction process of polyphenols from fruit shell of Metaplexis japonica ( Thunb.) Makino and preliminarily evaluate its antioxidant activity. Method: On the basis of single factor experiments, the extraction conditions of polyphenols were optimized by response surface methodology with the content of polyphenols as index. The antioxidant capacity was measured by reducing power, scavenging of hydroxyl radicals and DPPH. Result: The optimum extraction conditions were as follows: ethanol concentration ( v/v) was 42%, ratio of liquid to solid was 16 ∶ 1 ( m L/g) , extraction temperature was 61 ℃ and extraction time was 64 min. Under the conditions, the extraction amount of polyphenols was ( 26.86 ± 0.37) mg/10 g.The polyphenols had certain reducing power.When the concentration of polyphenols was 1 mg/m L, the clearance rate on hydroxyl radicals and DPPH· was 70.78% and 85.22%, respectively. Conclusion: The optimized technology was feasible and the polyphenols had certain antioxidant capacity.