Biological activity of two red algae, Gracilaria salicornia and Hypnea flagelliformis from Persian Gulf.

Among marine organisms, algae are a large and diverse group of organisms from which a wide range of secondary metabolites have been isolated. A number of these compounds possess biological activity. In this study, we aim to evaluate the cytotoxic, antibacterial and antifungal activity of two red algae, Gracilaria salicornia and Hypnea flagelliformis, collected from Persian Gulf. Ethyl acetate extracts of both algae showed a potent cytotoxic effect against Artemia salina nauplii (LC_{50 =} 3 and 4 μg.ml⁻¹, respectively). Aqueous methanol (50%) extracts were also effective. None of the methanol and aqueous methanol extracts of the algae showed antifungal and antibacterial activity against Staphylococcus aureus, Escherichia coli, Candida albicans and Aspergillus niger by the Broth-dilution method. Only the ethyl acetate extracts exhibited antibacterial activity (MIC = 2 μg.ml⁻¹) on S. aureus. In conclusion, G. salicornia and H. flagelliformis could be a promising source of cytotoxic components.