Green extraction approach for the recovery of polyphenols from Croatian olive leaves (Olea europea)

Pressurized liquid extraction (PLE) is shown as an innovative green technology for the effective extraction of the various phytochemicals from food by-products, therefore the aims of this study were to evaluate the application of PLE to engineer green extracts of Croatian olive leaves (Olea europaea, cv. Oblica) for potential industrial production (functional foods/pharmaceuticals). PLE was conducted under various cycle numbers (1, 2), temperature (60, 80, 100 degrees C) and static times (5, 10, 15 min). Obtained extracts were characterized in terms of: (i) total polyphenols (TP); (ii) total flavonoids (TF); hydroxycinnamic acids (HCA); and (iv) flavonols (FLA). Response surface methodology revealed optimal PLE parameters for polyphenols recovery, observing differences in the extraction conditions (number of cycles, temperature and time) according to the specific polyphenol groups. TP optimal extraction conditions (53.15 mg GAE/g) were achieved after PLE (2 cycles, 80 degrees C/5 min,) while 1 cycle with 100 degrees C/15 min were selected as the optimal PLE conditions for TF recovery (16.51 mg QE/g). For HCA, 2 cycle, 91 degrees C/15-min were the conditions with highest yields (1.66 mg CA/g); and for FLA extraction under 1 cycle, 87 degrees C/5-min revealed the highest recovery (8.66 mg QE/g). Results indicated PLE as a good choice for green recovering polyphenols from the olive leaves. (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.