An environmentally friendly process for the production of extracts rich in phenolic antioxidants from Olea europaea L. and Cynara scolymus L. matrices

Abstract

A sustainable extractive technology followed by membrane separation methods was applied to Olea europaea L. (leaves and pitted olive pulp) and Cynara scolymus L. by-products (leaves and stems), to obtain different standardized commercial extracts for application in the functional food industry, pharmaceutical and cosmetic fields. The entire treatment, PCT registered, consists of water extraction of the aforementioned vegetal material and the following steps of fractionation: (1) microfiltration (only for Olea); (2) ultrafiltration (only for Cynara); (3) nanofiltration (only for Olea); (4) reverse osmosis and final concentration by evaporation at low temperature or spray-dried technique. Thanks to these steps, different fractions enriched with phenolic compounds that have an economic value can be obtained. These fractions were characterized and quantified by HPLC/DAD-ESI/MS and then tested for their antiradical and antioxidant properties. The EC50 values by DPPH test were 6.76 × 10−3 mM for the Olea green leaves (GL) soft extract, 5.44 × 10−3 mM for the Olea dried leaves (DL) soft extract, and 1.22 × 10−3 mM in the case of the Olea OH-Tyr soft extract. The EC50 value of the Cynara GL soft extract was 3.25 × 10−3 mM. The ORAC results were 3632 ± 110.7 µmoL TE/g for OH-Tyr Olea soft extract, 1410 ± 62.1 µmoL TE/g for GL Olea soft extract, and finally 760 ± 12 µmoL TE/g for GL Cynara soft extract, confirming the highest antioxidant activity of hydroxytyrosol.