Extraction of antioxidants and flavonoids from yuzu (Citrus junos Sieb ex Tanaka) peels: a response surface methodology study

In the present investigation, extraction of antioxidants and flavonoids from the peels of yuzu fruit using a single factor experiment and a response surface methodology (RSM) based on central composite design was studied. Four independent variables were evaluated at five levels with total 29 experimental runs, including ethanol concentration (EtOH), ratio of liquid to material (L/S), extraction temperature (T), and extraction time (t). The total phenolic content (TPC), total flavonoids content (TFC), two indicators of antioxidant capacity (FRAP and DPPH), and three individual major flavonoids in yuzu (hesperidin, naringin, and phloretin) served as the response functions. Quadratic polynomial equations were obtained by multiple regression analysis to predict the optimal extraction conditions. The regression analysis showed that > 95 % of variations were explained by the models of different responses considered. The responses were significantly influenced by all studied factors. The Multiresponse optimized conditions targeted at maximizing all the responses were found to be EtOH = 65.550 %; T = 43.864 A degrees C; t = 119.673 min; and L/S = 37.168 ml/g, with a desirability of 0.950. At the optimized conditions, the experimental values of FRAP (964.9 +/- 23.1 mgTE/g DW), DPPH (453.0 +/- 5.2 mgTE/g DW), TPC (1161.2 +/- 25.2 mgGAE/g DW), (TFC393.4 +/- mgQE/g DW), hesperidin (337.2 +/- 4.0 mg/g DW), naringin (244.9 +/- 1.1 mg/g DW), and phloretin (43.9 mg/g DW) were in a reasonable agreement with the predicted values. The extraction method was applied successfully to extract antioxidants and flavonoids from yuzu peels. It also allows a fast and cost-saving process for extraction of the studied phytochemicals, in addition to improvement of the quantity of the targeted extract.