Discrimination of Farming Practices Through Olive Leaf Phenolic and Mineral Analysis

The content and composition of phenolic compounds and mineral elements in olive leaves are susceptible to variation influenced by various factors, such as genotype, environment, and agricultural practices. The aim of this study was to investigate and compare the response of phenolics and minerals to organic and integrated farming systems. Trees from three olive cultivars grown in two neighboring olive groves with different farming systems were used. After sampling during pruning in two consecutives sampling years, the contents of phenolics and minerals in olive leaves was determined by high-performance liquid chromatography (HPLC) and inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis, respectively. The obtained results revealed a complex response of both phenolics and minerals, strongly influenced by interactions among the factors, such as farming system, cultivar, and sampling year. Specific phenolic compounds, such as luteolin-4-O-glucoside and luteolin-7-O-glucoside, were particularly abundant under organic farming conditions. Others, like oleuropein and oleacein, followed a similar trend, though they were more strongly affected by different cultivar and sampling year combinations. A lower content of mineral elements was generally observed under organic farming conditions, although it was also significantly affected by cultivar and sampling year. The results of this study have the potential to be utilized for the enhanced production of organic olive leaves as a reliable source of valuable phytochemicals for nutraceuticals, functional foods, and dietary supplements.