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Enhancement of the green extraction of bioactive molecules from Olea europaea leaves

This study was aimed to compare the efficiency of conventional extraction (CE), micro-wave-assisted extraction (MWE) and microwave-ultrasound-assisted extraction (MWUE) for extraction of bioactive molecules from olive leaves using water as a solvent and to define the optimum extraction process conditions for all three used methods. Olive leaves are rich source of polyphenols that have beneficial anti-hipertensive, hypocholesterolemic, cardioprotective, and anti-inflammatory effects. CE conditions (temperature, time, magnetic stirrer rotational rate, and particle diameter), as well as MWE extraction and MWUE conditions (microwave power, time, particle diameter, and temperature), were optimized using response surface methodology (RSM) based on Box- Behnken design of experiment. Total polyphenolic content and antioxidant activities of all prepared extracts were analyzed and compared. Results showed that MWUE gave the highest amount of total polyphenols (TPC = 273.779 ± 4.968 mgGAE gd.m.-1) and the highest antioxidant activity approximately 3.1 times greater than CE. Optimal extraction conditions were estimated to be 80 ºC, 15 min, 200 μm and 750 min-1 for CE, 700 W, 7.5 min, 300 μm and 80 °C for MWE and 800 W, 5 min, 100 μm and 60 °C for MWUE. Considering the maximum amount of extracted total polyphenols results indicate the usage of the MWUE as the most effective green ex-traction process in which the highest amount of polyphenols was extracted and could be used by the food industry for commercial application of currently non-profitable plant sources.

olive leaves ; microwave-assisted extraction ; microwave-ultrasound-assisted extraction ; response surface optimization

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