Évaluation de l’activité antioxydante et antibactérienne de l'extrait de Chlorella vulgaris.

Abstract

This study aims to evaluate the antioxidant and antimicrobial activities of Chlorella vulgaris, a microalga recognized for its nutritional and therapeutic properties. The study focuses primarily on the extract obtained through ultrasound-assisted extraction, a technique that disrupts the algal cell wall in order to increase the yield of bioactive compounds. The results showed an extraction yield of 11.7%. Phytochemical analysis of the ethanolic extract of Chlorella vulgaris revealed the presence of several phenolic compounds, including polyphenols, flavonoids, tannins, and saponins, with an absence of reducing sugars. Quantitative analysis yielded total polyphenol content of 6.69 mg GAE/g DW, flavonoids at 26.33 mg QE/g DW, and condensed tannins at 24.90 mg CE/g DW. These compounds may be responsible for the observed biological activities. Antioxidant activity, assessed by the DPPH method, indicated weak antioxidant potential, with an IC₅₀ value estimated at 300.50 μg/ml. Antibacterial activity was evaluated using the disk diffusion method against four pathogenic strains, namely Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa. The results revealed no inhibitory activity, as none of the tested strains, whether Gram-positive or Gram-negative, exhibited sensitivity to the extract. These findings indicate that, under the experimental conditions of the present study, Chlorella vulgaris does not demonstrate significant activity as a source of antibacterial or antioxidant agents. This lack of efficacy may be attributed to the nature and origin of the raw material, the solvent employed, and the extraction method, all of which influence the composition and concentration of bioactive compounds.