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Set-up of sonotrode based extraction to recover phenolic compounds from olive leaves
Beatriz Martín García * 1 , Alegría Carrasco-Pancorbo 1 , Vito Verardo 2 , Lorenzo León 3 , Raúl De la Rosa 4 , Ana María Gómez-Caravaca 1
1  Department of Analytical Chemistry, Faculty of Sciences, University of Granada
2  Department of Nutrition and Food Science, University of Granada and Institute of Nutrition and Food Technology ‘José Mataix’, Biomedical Research Center, University of Granada
3  IFAPA Centro Alameda del Obispo, Avda Menéndez Pidal, s/n, Córdoba, E-14004, Spain
4  IFAPA Centro Alameda del Obispo, Avda Menéndez Pidal, s/n, E-14004 Córdoba, Spain

10.3390/foods_2020-07692 (registering DOI)
Abstract:

Olive leaves are a waste by-product obtained during the olive oil production and pruning. They contain phenolic compounds that possess antioxidative, antimicrobial, anti-atherogenic and anti-inflammatory properties, among others. For that reason, a procedure based on ultrasound-assisted extraction via sonotrode was developed to evaluate the recovery of these phenolic compounds from olive leaves. To establish the sonotrode extraction, a Box-Behnken design based on response surface methodology (RSM) was used to optimize the effects of factors such as solvent composition (30-100% EtOH), extraction time (1-10 min) and amplitude (20-100%). Qualitative and quantitative analyses of phenolic compounds were performed using HPLC coupled to DAD and mass spectrometer detectors. The highest content of phenolic compounds was 35.52 mg/g d.w. obtained using 55:45 ethanol/water (v/v), 8 minutes and 100% of the amplitude. The optimal conditions selected for the sonotrode were compared with the result obtained by a conventional ultrasonic bath achieving similar concentrations. Therefore, sonotrode could be considered as an efficient extraction technique that allows a good recovery of phenolic substances from olive leaf that could be easily scale-up at industrial level.

Keywords: Olive leaves, phenolic compounds, sonotrode, Box-Behnken, HPLC-MS
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