Potentiel Antioxydant et Activité de Piégeage des Radicaux Libres d'Extraits de Feuilles d'Olivier : Corrélation avec la Teneur en polyphénols Totaux.

Abstract

The olive tree (Olea europaea L.) is a Mediterranean species widely recognized for its richness in bioactive compounds, particularly polyphenols, which are known for their important antioxidant properties. This study aimed to evaluate the antioxidant potential and free radical scavenging activity of olive leaf extracts, as well as their correlation with total polyphenol content. Aqueous and 70% ethanolic extracts were obtained by cold maceration. The highest extraction yield was recorded for the ethanolic extract (12.3%). Phytochemical screening revealed the presence of several secondary metabolites, including polyphenols, flavonoids, and tannins. Quantitative analysis showed that the ethanolic extract contained higher levels, of phenolic compounds than the aqueous extract, with polyphenol contents ranging from 0.44 ± 0 to 7.00 ± 0.11 mg GAE/g, compared with 0.36 ± 0 to 4.08 ± 0.06 mg GAE/g, and flavonoid contents ranging from 0.90 ± 2.12 to 335.40 ± 4.24 mg QE/g, compared with 3.90 ± 2.12 to 86.40 ± 8.49 mg QE/g, respectively. Antioxidant activity was assessed using the DPPH assay, which demonstrated a concentration-dependent free radical scavenging activity, with the ethanolic extract exhibiting greater activity characterized by an IC₅₀ value of 1702.45 μg/mL, compared with 4476.14 μg/mL for the aqueous extract. The correlation study between total polyphenol content and antioxidant activity revealed positive but statistically non-significant correlations (p > 0.05). These findings suggest that olive leaves represent a promising source of bioactive compounds with antioxidant potential, with the ethanolic extract showing the highest performance under the experimental conditions investigated.