Abstract
SUMMARYThe beneficial properties of polyphenols are widely recognized, and polyphenol-rich olive oil, which is part of the typical Mediterranean diet, has been identified as having positive health effects. However, over the past decade, olive leaves have been discovered as an alternative polyphenol-rich source. This is particularly interesting in the context of the growing interest in functional foods, as well as in terms of the management of biological waste, including olive leaves that are left over from the production of olive oil. Previous studies on olive leaves confirmed that they have a high phenolic content, which explains their previously described strong antibacterial, antimicrobial and antiviral activity. Therefore, the major aim of our work is to comprehensively determine olive leaf phenolic content in cultivars Istarska bjelica, Leccino and Buža as a natural source of bioactive compounds suitable for daily consumption in the form of infusion. For this purpose, we examined the influence of olive leaf cultivar, maceration time and temperature on the phenolic composition of final infusions. Phenolic compounds were analysed by liquid chromatography (LC) coupled to a triple quadrupole mass spectrometer (LC-QQQ). As expected, the results indicate the significant influence of not only the olive cultivar but also of maceration parameters on the qualitative and quantitative phenolic composition. The highest phenolic compound content was obtained in the infusion of Istarska bjelica leaves after 15 min of maceration. However, the Buža olive leaf infusion had the most diverse phenolic composition. Furthermore, we designed several functional olive leaf infusion mixtures with phenolic compositions adjusted based on the desired health effect. The results show the role of phenolic composition adjustment in the development and improvement of the quality of functional olive leaf infusions.
Highlights
Polyphenols, as plant secondary metabolites, show a high degree of structural diversity
Total phenolic content was determined by summing up the mass fractions of all detected individual polyphenols
The results revealed that temperature and time had an evident effect on the mass fraction of extracted phenols (Fig. 1)
Summary
Polyphenols, as plant secondary metabolites, show a high degree of structural diversity. They are present and stored in plant tissues in the form of different derivatives, mainly as sugar O-glycosides [1]. Glycosylation ensures their structural stability during storage in the vacuoles and chloroplasts of plants. Olive leaves have not yet been sufficiently exploited in medical applications as a source of beneficial phenolics. The exploitation of olive leaves as a starting raw material in the production of functional food or other medical products may improve biological waste management
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