Antioxidant and Antibacterial Activities and Phytochemical Analysis of Olea europaea subsp. laperrinei Leaves Extracts

Olea europaea subsp. laperrinei, endemic to the central Sahara in Algeria, Niger, and Sudan, is recognized for its therapeutic and nutritional benefits, notably its antioxidant and antibacterial properties. This study investigates the phytochemical composition and biological activities of its leaf extracts obtained via aqueous and ethanolic extraction. Total phenols, flavonoids, and tannins were quantified by UV–visible spectrophotometry, while individual phenolic compounds were identified by HPLC-UV. Antioxidant capacity was measured using DPPH radical scavenging, hydrogen peroxide neutralization, and β-carotene bleaching assays. Antibacterial activity was evaluated against nine bacterial strains. The ethanolic extract exhibited higher total phenol (134.72 ± 9.25 mg GAE/g VP) and flavonoid (26.08 ± 1.57 mg QE/g VP) contents, while tannin levels were similar in both extracts. Twenty-seven phenolic compounds, including oleuropein, hydroxytyrosol, rutin, and quercetin, were identified. The ethanolic extract showed superior antioxidant capacity, with an EC50 of 7.48 ± 0.39 µg/mL (DPPH) and IC50 values of 214.04 ± 2.89 µg/mL (H2O2) and 185.63 ± 3.84 µg/mL (β-carotene). Both extracts exhibited antibacterial effects, with inhibition zones up to 23.33 ± 0.76 mm and MIC values as low as 0.78 mg/mL. These findings highlight the potential of Laperrine olive leaves as natural antioxidant and antibacterial agents.