Phytochemical Screening, Antimicrobial, and Antioxidant Activities of Olea europaea Leaf Extracts

Olea europaea L. (family Oleaceae) is a medicinal plant traditionally used to manage infections, hypertension, diabetes, and inflammatory conditions. This study evaluated the phytochemical composition, antimicrobial, and antioxidant activities of O. europaea leaves. Dried leaves were sequentially extracted using n-hexane, methanol, and water. Phytochemical screening revealed that methanolic and aqueous extracts contained phenolics, flavonoids, tannins, saponins, alkaloids, and cardiac glycosides, whereas n-hexane lacked cardiac glycosides and steroids. Antimicrobial activity was assessed against Salmonella spp., Escherichia coli, Aspergillus niger, and Candida albicans using the agar well diffusion method, with Ceftriaxone (10–30 mg/mL) and fluconazole (10–30 mg/mL) as controls. Minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) were determined by broth dilution. All extracts exhibited antimicrobial activity, with inhibition zones of 0–2.9 mm (bacteria) and 0–2.8 mm (fungi). Methanolic extract demonstrated the highest antibacterial activity against Salmonella spp. (2.20 mm at 30 mg/mL), while the aqueous extract showed the strongest antifungal activity against C. albicans (2.80 mm at 30 mg/mL). MICs ranged from 0.05 to 8.56 mg/mL and MFCs from 0.56 to 14.32 mg/mL. Antioxidant activity, measured by DPPH free radical scavenging (5–640 µg/mL), was concentration-dependent, with methanolic extract achieving 87.36% inhibition at 640 µg/mL. These findings indicate that O. europaea leaves are a rich source of bioactive compounds with moderate  antimicrobial and potent antioxidant properties, highlighting their potential as natural therapeutic agents for managing infections and oxidative stress-related conditions.