Unlocking the Value of Nine Olive Leaf Varieties: A Dual Assessment of Phenolic Composition and Antioxidant Properties

Olive leaves are a valuable source of natural bioactive compounds, particularly polyphenols and flavonoids, recognized for their potent antioxidant and health-promoting properties. The extraction of these high-value products has gained increasing attention due to their relevance in food sustainability and the circular economy. However, the concentrations and profiles of these compounds vary substantially depending on the olive variety and the extraction method applied. This study evaluated the influence of extraction method and olive variety on the phenolic composition and antioxidant potential of olive leaf extracts from nine cultivars cultivated in Morocco. Two conventional extraction techniques, maceration and Soxhlet extraction, were compared for their efficiency in recovering extraction yield, total phenolic content, total flavonoid content, and total condensed tannins, along with antioxidant activity measured by DPPH and ABTS radical scavenging assays. Analyses of variance indicated that varietal differences were the predominant source of variation in phenolic composition and antioxidant capacity, whereas the extraction method mainly influenced yield. Soxhlet extraction enhanced phenolic recovery and antioxidant potential, while maceration favored flavonoid extraction. These findings highlight the potential of olive leaf extracts derived from Manzanilla, Haouzia, Picual, and Moroccan Picholine varieties using Soxhlet as sustainable natural antioxidants for functional, cosmetic, and pharmaceutical uses.