Résumé:
The aim of this work is the search for new bioactive natural compounds with an evaluation of the antibacterial activities of the crude extract of two red algae Jania rubens and Laurencia obtusa harvested from the west coast of Mostaganem at the Stidia Bay, against three bacterial strains (Gram-positive: Staphylococcus aureus) and (Gram-negative: Klebsiella pneumoniae and Pseudomonas aeruginosa). The results obtained after different extractions with two solvents methanol and chloroform enabled us to calculate the yield of crude extract evaluated at (18.6%). The quantitative determination of the main classes of secondary metabolites made it possible to record a high content of flavonoids, an average content of total phenols, and low content of tannins. The evaluation of the antibacterial effect shows that most of the bacterial strains tested are sensitive to the Jania rubens algae extract and the extract of Laurencia obtusa. The best zones of inhibition are obtained by the bacterial strain Klebsiella pneumoniae about the strains tested with a diameter of 18 mm with the extract of Jania rubens and a zone of 22 mm with the extract of Laurencia obtusa. These results suggest that Jania Rubens extract has a very significant inhibitory effect against certain pathogens
