Innovative Extraction Technologies for Development of Functional Ingredients Based on Polyphenols from Olive Leaves

Abstract

Olive tree (Olea europea L.) leaves represent around 10% of the total weight of olives arriving at any given mill, which are generally discarded, causing economic and environmental issues. However, these are rich sources of natural bioactive compounds (i.e., polyphenols), which have health-promoting potential. Thus, the valorization of olive leaves by recovering and reusing their components should be a must for food sustainability and circular economy. This review provides an insight into the principal polyphenols present in olive leaves, together with agronomic variables influencing their content. It also summarizes the recent advances in the application of novel extraction technologies that have shown promising extraction efficacy, reducing the volume of extraction solvent and saving time and cost. Moreover, potential industrial uses and international patents filed in the pharmaceutic, food, and cosmetic sectors are discussed.

Antioxidant and Antimicrobial Activity of Hydroethanolic Leaf Extracts from Six Mediterranean Olive Cultivars

“…The main by-products are leaves, the amount of which depends on different factors, such as olive tree cultivar, environmental conditions, tree age, pruning practices, etc. [ 1 , 2 , 3 , 4 ], often leading to serious economic and environmental problems for producers. However, olive leaves could be converted into value-added products, rich in different phytochemicals and/or converted biofuels using chemical/biochemical methods [ 3 ].…”

Development of muffin with the incorporation of olive pomace flour, extra virgin olive oil and hydrolyzed soy protein

“…However, its composition includes the significant presence of carbohydrates, proteins, fatty acids, minerals, vitamins, pigments and bioactive compounds, especially the phenolic compounds (Lechhab, Lechhab, Cacciola, & Salmoun, 2022;Medeiros, Villa, Silva, & Júlio, 2016;Rodrigues et al, 2015). Most of the phenolic compounds (~98 %) are composed of secoiridoids (glycosylated oleuropein), phenolic alcohols (tyrosol and hydroxytyrosol), hydroxycinnamic acid (verbascoside) and flavonoids (quercetin as flavonols; luteolin-7-O-glucoside, apigenin-7-O-glucoside and diosmetin-7-O-glucoside as flavones) (Ballus et al, 2015;Clodoveo, Crupi, Annunziato, & Corbo, 2021;Expósito-Díaz et al, 2022; (Figure 1) and remain in the bagasse, which can be a natural and low-cost source for use in the food industry as bioactive ingredients (Nunes et al, 2019). The technological application of olive residue requires that the pomace be dehydrated before use to a moisture content of less than 15 % on a dry basis, to avoid product deterioration by bacteria and fungi (mainly molds).…”

Organosolv Treatment/Polyphenol Extraction from Olive Leaves (Olea europaea L.) Using Glycerol and Glycerol-Based Deep Eutectic Solvents: Effect on Metabolite Stability

“…The extraction processes developed to extract polyphenolic compounds from plant material rely on solid-liquid techniques, deployed according to the nature of the compounds to-be-extracted, the cost, properties, and toxicity of suitable solvents, but also the unit operations required, the purity of the product, etc. In the framework of Green Chemistry, the use of alternative solvents (i.e., deep eutectic solvents-DES) and technologies (i.e., ultrasound irradiation, microwave heating) are gaining acceptance for establishing benign protocols for solid-liquid extraction, and on such a basis a high number of extraction procedures have been proposed for polyphenol recovery from olive leaves [12]. One of the major objectives for applying techniques such as ultrasonication, is the disruption of plant cell walls, in order to facilitate release of intracellular metabolites and their entrainment into the liquid phase [13].…”