Olive Leaf Extracts from Three Italian Olive Cultivars Exposed to Drought Stress Differentially Protect Cells against Oxidative Stress

Olive leaves are an abundant by-product of olive oil production. Olive leaf extracts(OLEs) are rich in polyphenols, which can be used for health benefits. As polyphenols are the mainantioxidant molecules in plants, plants typically increase their polyphenol content when exposed todrought stress. However, the phenolic profile of OLEs can vary in relation to the origin and variety ofthe plant material. In this work, olive leaf extracts from three different Italian olive cultivars (Giarraffa,Leccino, and Maurino) both exposed and not exposed to drought stress were studied in terms ofantioxidant properties and profile, intestinal permeation, and protection against oxidative stress ofhuman umbilical vein endothelial cells (HUVECs), since HUVECs are considered a model to study awide range of diseases. OLEs from stressed Maurino and Giarraffa plants showed the highest increasein antioxidant capacity compared to controls. The phenolic profile of Maurino' was mainly increasedby water deficit, with a large increase in the compounds oleuropein and luteolin-7-O-rutinoside. Alltested extracts exposed to a water deficit protected HUVECs against oxidative stress by reducing ROSproduction, and this effect was more pronounced in OLEs from Giarraffa and Maurino exposed todrought stress compared to all other extracts. Finally, OLE from the stressed Giarraffa group showeda higher apparent permeability of antioxidant molecules than that of Maurino.