Abstract
The aim of the present study was to improve the recovery of polyphenols from olive leaves (OL) by optimizing a multistage extraction scheme; provided that the olive leaves have been previously steam blanched. The maximum total phenol content expressed in ppm caffeic acid equivalents was obtained at pH 2, particle size 0.315 mm, solid-liquid ratio 1:7 and aqueous ethanol concentration 70% (v/v). The optimum duration time of each extraction stage and the operation temperature, were chosen based on qualitative and quantitative analysis of oleuropein (OLE), verbascoside, luteolin-7-O-glucoside and apigenin-7-O-glucoside performed by high performance liquid chromatography with diode array detector (HPLC-DAD). The optimum conditions for multistage extraction were 30 min total extraction time (10 min × 3 stages) at 85 °C. The 80% of the total yield of polyphenols was obtained at the 1st stage of the extraction. The total extraction yield of oleuropein was found 23 times higher (103.1 mg OLE/g dry weight (d.w.) OL) compared to the yield (4.6 mg OLE/g d.w. OL) obtained by the conventional extraction method (40 °C, 48 h). However, from an energetic and hence from an economical point of view it is preferable to work at 40 °C, since the total extraction yield of polyphenolic compounds was only 17% higher for a double increase in the operating temperature (i.e., 85 °C).
Highlights
By-products and wastes from plant food processing, which represent a major environmental problem in Mediterranean countries, are sources of added value bioactive compounds called phytochemicals or secondary metabolites [1]
In preliminary experiments the total phenol content (TPC) of ethanolic extracts of olive leaves was determined with Folin-Ciocalteau assay and HPLC-DAD
It should be noted that when the extraction temperature was ≤40 °C there were no qualitative changes of the phenolic profile of the extracts and Folin-Ciocalteau assay was preferred as an easy and fast procedure for the optimization of extraction in terms of pH, particle size, solid-to-liquid ratio (S/L) and ethanol concentration (% EtOH, v/v)
Summary
By-products and wastes from plant food processing, which represent a major environmental problem in Mediterranean countries, are sources of added value bioactive compounds called phytochemicals or secondary metabolites [1]. Among the different parts of the olive tree, olive leaves possess the highest oleuropein content, within a range of 1%–14% compared to olive oil (0.005%–0.12%) and olive mill wastewater (0.87%) [4]. Several studies have revealed that the health-promoting properties of virgin olive oil are mainly due to the presence of polyphenolic compounds [5]. Oleuropein and related phenolic compounds (e.g., luteolin-7-glucoside, apigenin-7-glucoside, hydroxytyrosol and rutin) have shown cardiovascular protective effects [6,7]. A possible explanation for these effects of olive leaves polyphenols has been attributed to the synergistic phenomena among the phenolic compounds [8]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
