A green microwave-assisted extraction of high value-added compounds from exotic fruits’ peels was optimized by Box-Behnken design using 3 factors: solid/solvent ratio, X1, temperature, X2, and extraction time, X3. By using Derringer’s desirability function, optimum extraction yields are obtained with X1 = 1/149.95 g/mL, X2 = 72.27 °C and X3 = 39.39 min (white-fleshed red pitaya) and X1 = 1/148.96 g/mL, X2 = 72.56 °C and X3 = 5.02 min (yellow pitaya) and a maximum betacyanin content is achieved with X1 = 1/150 g/mL, X2 = 49.33 °C and X3 = 5 min. None of the factors influenced the extraction of phenolic compounds. Eighteen cinnamoyl derivatives, 17 flavonoid derivatives and 4 betacyanins were identified by HPLC–DAD–ESI/MSn, 23 and 15 new compounds being described in yellow and white-fleshed red pitayas, respectively. These results indicate that it is possible to reuse these by-products to recover compounds for food and pharmaceutical industries.
.. 2. Materials and methods. 2.1. Chemicals and standards. Acetonitrile and formic acid were bought from Merck (Darmstadt, Germany) and VWR (Fontenay-sous-Bois, France), respectively. 4-O-Caffeoylquinic acid was purchased from Chengdu Biopurify Phytochemicals Ltd. ...
