Evaluation de l’activité biologique des extraits d’une plante médicinale.

Abstract

The objective of our work is the phytochemical study and the evaluation of the biological activities (antioxidant and antibacterial) of aqueous and hydro-ethanolic extracts of the flower buds of clove (Syzygium aromaticum L.). The highest extraction yield was recorded with the hydro-ethanolic extract (25.2%), while the aqueous extract showed a yield of (11,7%). Phytochemical screening revealed the presence of tannins, saponins, polyphenols, flavonoids, alkaloids, quinones, mucilage, and proteins. Quantitative analysis of both extracts revealed significant differences in the concentration of bioactive compounds. The hydro-ethanolic extract was richer in polyphenols (26,78±0,19μg EAG/mg) compared to the aqueous extract (19,59±0,03μg EAG/mg). On the other hand, the aqueous extract exhibited higher levels of flavonoids (20.38±0.03μg QE/mg) than the hydro-éthanolic extract (14,14±0,01μg EQ/mg), as well as higher levels of flavones and flavonols (50.79±0,15μg QE/mg vs 44.73±0,11μg QE/mg). The tannin content was relatively similar between the two extracts (34.52±0,002μg CE/mg) for the aqueous extract and (33.88±0 ,003μg CE/mg) for the hydro-ethanolic extract. These results reflect the influence of solvent polarity on the extraction efficiency of bioactive compounds. The antioxidant activity of the extracts was evaluated using the DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging assay, which allowed the determination of IC50 values for each extract. The hydroethanolic extract showed stronger antioxidant activity with an IC50 of 33.20±0,003μg/mL, compared to 113.41±0,003μg/mL for the aqueous extract. Finally, the antibacterial activity of both extracts was tested against four Gram-positive and Gram-negative bacterial strains: Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, and Staphylococcus aureus, at different concentrations. However, no inhibitory effect was observed against the tested strains.