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Foods 2018, 7(9), 149; https://doi.org/10.3390/foods7090149

Optimization of Ultrasonic-Assisted Extraction of Major Phenolic Compounds from Olive Leaves (Olea europaea L.) Using Response Surface Methodology

1
Department of Biotechnology, University of Rijeka, Radmile Matejčić 2, 51000 Rijeka, Croatia
2
Department of Medical Physics and Biophysics, Faculty of Medicine, University of Rijeka, Braće Branchetta 20, 51000 Rijeka, Croatia
3
Department of Physics, University of Rijeka, Radmile Matejčić 2, 51000 Rijeka, Croatia
*
Author to whom correspondence should be addressed.
Received: 14 August 2018 / Revised: 31 August 2018 / Accepted: 3 September 2018 / Published: 6 September 2018
(This article belongs to the Special Issue Novel Food Processing and Extraction Technologies)
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Abstract

The ultrasound-assisted extraction (UAE) of oleuropein (OLE), verbascoside (VER), and luteolin-4′-O-glucoside (L4OG), as the major phenolics from olive leaves, was optimized using response surface methodology (RSM). A Box–Behnken design (BBD) was used to monitor the effect of different modes of ultrasound operation (pulsed and continuous), liquid–solid (L–S) ratio, and sonication time on each phenolic yield. The yield of UAE and conventional solid extraction (CSE) was determined after performing ultrahigh-performance liquid chromatography with a diode-array detector (UHPLC-DAD) analysis on the extracts. The results suggested that, under optimal conditions, the concentrations of OLE, VER, and L4OG were 13.386, 0.363, and 0.527 mg/g of dry powdered olive leaves (DPOL), respectively. Verification of experiments was carried out under the modified optimal conditions and the relative errors between the predicted and experimental values were dependent on the examined phenolic compound (OLE 8.63%, VER 11.3%, and L4OG 22.48%). In comparison with CSE, UAE improved the yields of OLE, VER, and L4OG (32.6%, 41.8%, and 47.5%, respectively, after 1 min) at a temperature of 60 °C, an L–S ratio of 15 (v/w), and in the continuous mode of UAE. We demonstrated that the UAE technique is an efficient method for enhancing yields of OLE, VER, and L4OG in olive-leaf extracts, while the chosen model was adequate to optimize the extraction of major phenolic compounds from olive leaves. View Full-Text
Keywords: ultrasound-assisted extraction; response surface methodology; olive leaves; oleuropein; verbascoside; luteolin-4′-O-glucoside ultrasound-assisted extraction; response surface methodology; olive leaves; oleuropein; verbascoside; luteolin-4′-O-glucoside
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Giacometti, J.; Žauhar, G.; Žuvić, M. Optimization of Ultrasonic-Assisted Extraction of Major Phenolic Compounds from Olive Leaves (Olea europaea L.) Using Response Surface Methodology. Foods 2018, 7, 149.

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