Evolution of Phenolic Compounds and Antioxidant Capacity of Olive Leaf (Olea europaea L.) Remaining on Branches After Pruning

Olive leaves (Olea europaea L.) are an important by-product of olive pruning and oil production and a rich source of phenolic compounds with antioxidant properties. However, their post-pruning biochemical evolution when leaves remain attached to branches is poorly understood. This study evaluated the changes in phenolic composition and antioxidant capacity of Cornicabra olive leaves attached to the branches during five months after pruning under intensive and super-intensive cultivation systems. Phenolic compounds were analyzed by HPLC-DAD and antioxidant capacity was assessed using DPPH and ORAC assays. Oleuropein was the main compound, followed by verbascoside and hydroxytyrosol derivatives. Both phenolic content and antioxidant capacity showed a clear temporal decline after pruning, with maximum values occurring within the first 6–24 days. The super-intensive system consistently showed higher levels than the intensive one. Antioxidant capacity closely followed phenolic behavior, with strong positive correlations, particularly for oleuropein and hydroxytyrosol compounds. Overall, olive leaves maintain high biochemical activity shortly after pruning, and the first 2–3 weeks represent the optimal period for their valorization. These results support improved management strategies and the use of olive leaves as a sustainable source of bioactive compounds.