Abstract
Olive leaves (OLL) represent a major waste generated during the production of olive oil, but there is a great potential for their valorization, because they provide important content in polyphenolic phytochemicals, which possess several bioactivities. In spite of the high number of studies dealing with polyphenol recovery from olive leaves, green processes involving environmentally benign solvents are scarce. In this study, a novel renewable natural low-transition temperature mixture (LTTM), composed of glycerol and sodium-potassium tartrate, was tested for its efficient ability to extract polyphenolic substances from OLL. The extraction process was optimised by using response surface methodology and the maximum yield in total polyphenols was 26.75 ± 3.22 mg caffeic acid equivalents per g dry weight, achieved with 50% (v/v) aqueous LTTM, liquid-to-solid ratio of 45 mL g−1 and at 73 °C. The LTTM was proven to be equally effective with 60% aqueous methanol, but it displayed inferior antioxidant properties. Liquid chromatography-diode array-mass spectrometry analyses revealed no significant qualitative differences between the LTTM and the aqueous methanolic extract.
Highlights
It is nowadays regarded central to the emerging bioeconomy that the residual biomass originating from the agricultural and food sector should not be treated as waste, but rather as a bioresource with high potential for the production of precious chemicals and fuels
An low-transition temperature mixture (LTTM) composed of glycerol, sodium-potassium tartrate tetrahydrate (SPT) and water at a molar ratio of 5:1:4 was tested for its efficiency in extracting polyphenolic antioxidants from various agri-food wastes, including Olive leaves (OLL) [5]
Tested in this amounts study was demonstrated be might efficient with impact the antioxidant properties of the extracts obtained, as indicated by comparison with the
Summary
It is nowadays regarded central to the emerging bioeconomy that the residual biomass originating from the agricultural and food sector should not be treated as waste, but rather as a bioresource with high potential for the production of precious chemicals and fuels. A prominent class of phytochemicals of abundant occurrence in agri-food wastes is polyphenols, encompassing an outstanding diversity of structures [1] Numerous of these compounds possess biological properties of particular interest, including anti-inflammatory and chemopreventive activities [2] and they are considered to have a significant prospect as bioactive agents in food, pharmaceutical and cosmetics industry. In the framework of deploying eco-friendly procedures for purposes of solid-liquid extraction of precious chemicals, a new generation of solvents, termed low-transition temperature mixtures (LTTMs) or deep eutectic solvents (DES), appears as a very promising path These novel materials are composed of non-toxic, natural and renewable substances and have attracting properties not encountered with conventional volatile solvents, such as low vapour pressure, absence of flammability and low cost [4]. The extracts obtained were evaluated for antioxidant activity and the principal phenolics were tentatively identified by liquid chromatography-diode array-mass spectrometry
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