Comparative study of the content of phenolic compounds in olive fruits and leaves for possible use in breeding programs for the functional selection of olive cultivars

Olive breeding has traditionally focused on the agronomic traits but the increasing number of scientific proofs supporting the positive impact of virgin olive oil (VOO) consumption on human health has made the functional quality of this product to be considered as an olive breeding target, particularly regarding the phenolic fraction of VOO. The presence of phenolic compounds in VOO is based mainly on the content of phenolic glucosides initially present in the olive fruit tissues and on the activity of hydrolytic and oxidative enzymes acting on these glucosides during the VOO extraction process. Thus, data on olive fruit phenolic composition would be of interest in olive breeding programs with the aim of obtaining new cultivars with improved functional quality. Taking into account that the main phenolics in olive fruits are essentially similar to those found in olive leaves, the objective of the present work was to carry out a comparative study of the phenolic fraction of fruits and leaves in selected cultivars characterized by having different contents of phenolic compounds in the oils to find out if the early selection of olive seedlings could be possible through an analysis of the phenolic compounds of their leaves. Results of the study showed that there is no correlation between the level of the fruit and leaf phenolics for the different olive cultivars. In addition, no significant correlation was found between the content of tyrosol and hydroxytyrosol derivatives in the leaves of the different olive cultivars over time as it does in the case of the fruits during the ripening process. These preliminary data pointed out that although the biosynthesis of the major olive phenolics is carried out through similar biochemical pathways, they seem to be regulated differently in the different organs of the plant.