Optimization of the recovery of high-value compounds from pitaya fruit by-products using microwave-assisted extraction.

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=1/149.95g/mL, X2=72.27°C and X3=39.39min (white-fleshed red pitaya) and X1=1/148.96g/mL, X2=72.56°C and X3=5.02min (yellow pitaya) and a maximum betacyanin content is achieved with X1=1/150g/mL, X2=49.33°C and X3=5min. 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/MS(n), 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.