Criblage phytochimique et activité antimicrobienne des extraits aqueux et méthanolique des feuilles de l’olivier (Olea europaea L.)

Abstract

The olive tree (Olea europaea L.) is an emblematic and millennial tree, deeply rooted in the history and culture of the Mediterranean basin. Belonging to the Oleaceae family, it is widely cultivated for its fruits, olives, which are consumed directly or processed into olive oil, a pillar of the Mediterranean diet renowned for its health benefits. The olive tree is also known for its persistent, coriaceous leaves rich in bioactive compounds. These leaves have been traditionally used in popular medicine for their various properties, notably their antioxidant and anti-inflammatory virtues. This study explored the antimicrobial potential of olive leaves, with the aim of validating the effectiveness of their bioactive compounds against infectious diseases. The extracts were obtained by cold maceration with two solvents methanol and water, revealing that the methanolic extract was more efficient (yield of 13%) and the qualitative analysis of these extracts by preliminary tests revealed the presence of phenolic compounds, tannins, flavonoids in the two extracts, to reveal the presence of phenolic compounds, tannins, flavonoids in the two extracts. This is confirmed by a quantitative analysis based on the determination of phenolic compounds, tannins, and flavonoids whose values: for phenolic compounds (0.809 0.001 mg GAE/g extract), tannins (0.639 0.112 mg CE/g extract) and flavonoids (12.477 0.608 mg QE/g extract) in the methanolic extract, and (1.035 0.001 mg GAE/g extract), (0.589 0.004 mg CE/g extract), (3.812 1.469mg QE/g extract) respectively in the aqueous extract . Antimicrobial in vitro tests demonstrated by the well diffusion method in a agar medium a powerful antibacterial activity of the extracts against Gram-positive (Staphylococcus aureus, with inhibition zones of 17 and 15 mm) and Gram-negative strains (Klebsiella pneumoniae, 18 mm; Proteus mirabilis, 20 mm; Pseudomonas aeruginosa, 10 mm). In addition, significant antifungal activity was observed against Candida albicans, with areas of inhibition exceeding 15 mm and a MIC of 12.5 mg/mL for the methanolic extract. These results highlight the potential of olive leaves as a source of antimicrobial compounds. This discovery opens promising prospects for their application in the development of new therapeutic strategies to combat microbial infections