Green Algae Halimeda macroloba in Spermonde Archipelago: Phytochemical and in vitro Antibacterial Studies

Background: Green algae Halimeda macroloba compounds active against human, fish, and shrimp pathogenic bacteria. It is one of the marine natural organisms (MNO) which is a diverse source of secondary metabolites. Objective: We have set our goal towards determining the antimicrobial potential of crude extracts of green algae H. macroloba. Materials and Methods: Three crude mixtures of Marine Natural Product (MNP) were obtained from macroalgae Halimeda macroloba (Lae-Lae island, Spermonde Archipelago) by extraction (n-hexane, ethyl acetate, and methanol were used as solvents). Results: Theses mixtures (phytochemical tests showed they contained steroids, terpenoids, and alkaloids) were screened for their activity against shrimp pathogenic bacteria (Vibrio harveyi (M-120), Aeromonas hydrophilla and Vibrio parahaemolyticus (T-170)). The obtained results confirmed weak antibacterial activity of studied extracts of H. macroloba. The ethyl acetate extract was the most potent antimicrobial agent at a concentration of 4 μg/25 μl. The inhibition zones for the growth of A. hydrophilla (the most susceptible microorganism) and V. harveyi were at 8.27 mm and 8.23 mm, respectively (inhibition zone was 15.2 mm for ciprofloxacin which was used as a positive control). Conclusion: They might be even used in the future as alternatives to conventional drugs in aquaculture.