Abstract
The aim of this study was to optimize the extraction of oleuropein from olive leaves through a systematic study of the effects of different parameters of ultrasound‐assisted extraction (USAE) on the oleuropein yield, in comparison with conventional maceration extraction. A range of operational parameters were investigated for both conventional maceration extraction and USAE: solvent type, olive leaf mass‐to‐solvent volume ratio, and extraction time and temperature. Oleuropein yield was determined using high‐performance liquid chromatography, with total phenolics content also determined. The optimized conditions (water–ethanol, 30:70 [v/v]; leaf‐to‐solvent ratio, 1:5 [w/v]; 2 hr; 25°C) provided ~30% greater oleuropein extraction yield compared to conventional maceration extraction. The total phenolics content obtained using the optimized USAE conditions was greater than reported in other studies. USAE is shown to be an efficient alternative to conventional maceration extraction techniques, as not only can it offer increased oleuropein extraction yield, but it also shows a number of particular advantages, such as the possibility of lower volumes of solvent and lower extraction times, with the extraction carried out at lower temperatures.
Highlights
In recent years, the agronomic, cosmetic, and pharmaceutical industries have increased their interest in natural extracts from plants and by-products that are rich in bioactive compounds
Olive leaves are a promising vegetable matrix, from which natural extracts can be obtained that are rich in a large variety of bioactive compounds, as they are rich in phenolic compounds
We investigate the application of ultrasound- assisted extraction (USAE) and the different extraction parameters such as type of solvent, ratio of olive leaf mass to solvent volume, and extraction time and temperature
Summary
The agronomic, cosmetic, and pharmaceutical industries have increased their interest in natural extracts from plants and by-products that are rich in bioactive compounds This is due to the need to meet the growing demand for natural preservatives and to produce novel functional foods with significant health benefits (Joana Gil-Chávez et al, 2013; Ribeiro, Estanqueiro, Oliveira, & Sousa Lobo, 2015; Soler-Rivas, Espín, & Wichers, 2000). In this respect, olive leaves are a promising vegetable matrix, from which natural extracts can be obtained that are rich in a large variety of bioactive compounds, as they are rich in phenolic compounds. Several studies have shown a wide variety of in vitro and in vivo properties for oleuropein, including antioxidant, antiviral, antibacterial, and anti- inflammatory activities
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