Antibacterial activities of bioactive compounds extracted from Marine algae Gracilaria salicornia against Aeromonas hydrophila

Herbal medicinal products have attracted significant research interest in recent years. Considering the efficiency of algae products in controlling pathogenic bacteria and also easy access to large resources of algae, this study was conducted to evaluate the effects of methanolic, chloroformic and aqueous extracts of Gracilaria salicornia against Aeromonas hydrophila, a heterotrophic, Gram-negative, rod-shaped bacterium found mainly in warm climate. Algae samples were collected from Qeshm Island coastlines and transferred to the laboratory. Standard methods were used to obtain the algae extract. Antibacterial activities of various extracts were tested against the bacterium using well diffusion assay method. Significant differences were observed in antibacterial activities of different extracts (P<0.05). The diameter of zone of growth inhibition varied in correlation with concentration of the extracts (50, 100, 200 and 300 mg.ml^-1). The best inhibition zone was observed at 100, 200 and 300 mg.ml^-1 methanolic and 300 mg.ml^-1 aqueous extracts.