Pressurized green liquid extraction of betalains and phenolic compounds from Opuntia stricta var. Dillenii whole fruit: Process optimization and biological activities of green extracts

The Opuntia Stricta var. Dillenii's prickly pears are an underutilized fruits, which provide a great source of betalains (mainly, betacyanins) and phenolic compounds (phenolic acids and flavonoids) that could play an important role in health-promotion. This study focuses on the optimization of process for the green extraction of betalains and phenolic compounds from Opuntia stricta var. Dillenii's whole fruits by Pressurized liquid extraction (PLE), using a response surface methodology (RSM) by a central composite design (CCD) in order to obtain rich extracts in betalains and phenolic compounds with the similar profile of the original one found in O. dillenii fruits (avoiding any degradation of these compounds during the extraction process) with proven biological activities. For PLE optimization, the ethanol volume in water (0-100%, v/v) and the temperature (25-65C) were selected as independent variables. The identification and quantification of the individual bioactive compounds of the obtained green extracts were done by HPLC-DAD-ESI/MS and HPLC-DAD-ESI/QTOF and their biological activities were determined by in vitro tests, as: the antioxidant activity by the ORAC method and the anti-inflammatory activity by the hyaluronidase inhibition method. Ethanol volume in water (%, v/v) was the var-iable with most significant (p <= 0.05) effect in the target responses (bioactive content and biological activities). The best results were obtained at 50% ethanol in water (v/v) and 25C temperature (run 10) obtaining extracts with betalains as 2.34 & PLUSMN; 0.18 mg of betanin/g dry weight, 2.51 & PLUSMN; 0.04 mg of 5' acute accent -O-E-sinapoyl-2'-apyosil-phyl-locactin/g dry weight, 2.32 +/- 0.19 mg of neobetanin/g dry weight and phenolic compounds, 2.08 & PLUSMN; 0.07 mg of piscicid acid/g dry weight and 0.25 +/- 0.02 mg of isorhamnetin glucoxyl-rhamnosyl-pentoside (IG2) /g dry weight. The betalain and phenolic profile of the PLE extracts was quite similar to the profile from the conven-tional extraction, but PLE extraction process enhanced the extraction of some bioactives as neobetanin (39%) andpiscidic acid (124%). All employed PLE process CCD combinations significantly upgrade the in vitro bio-logical activities (antioxidant and anti-inflammatory) of the Opuntia stricta var. Dillenii's PLE green extracts.