Marine algae synthesize a wide variety of chemically active secondary metabolites, which are an important source of products used by humans for therapeutic purposes. The objective of this study is to evaluate the antibacterial efficacy of the seaweed extracts at three different harvesting sites located on the coast of Moroccan Atlantic, to select active species and best site of collect. The chemical constituents of selected macroalgae have been investigated. For that, agar well diffusion assay was used to determine the antibacterial potential of the extractable matter against multi-resistant bacteria, two gram negative bacterium (Escherichia coli ATCC 10536 and Proteus mirabilis NIH) and two gram positive bacteria (Staphylococcus aureus CECT 976 and Staphylococcus aureus ATCC 25923), subsequently the MIC was determined.
Obtained results demonstrated that antibacterial activity of algae was influenced by solvent extraction and harvested site, the extracts of Pterosiphonia complanata collected from Sidi Bouzid were more efficiency against the strains studied in comparison with the same algae harvesting in three other sites. Compared to standards antibiotics, this alga extracted in dichloromethane/methanol, exhibited a stronger activity with (MIC of 0.02 µg/ml against Proteus mirabilis (NIH), 0.3 µg/ml against Staphylococcus aureus CECT 976 and 1.8 µg/ml against the Staphylococcus aureus ATCC 25923.
GC/MS analysis the Dichloromethan/Methanolic extract of Pterosiphonia complanata collected of Sidi Bouzid site indicated the existence of different constituents revealing environmental impacts. Presence of two major components including n-Hexadecanoic acid (palmitic acid) (15.68%) and Neophytadiene (12. 35%). Most of the identified components have antimicrobial activity, which may be responsible for the antibacterial potential reported in this study.