In this work, the antibacterial and lethal bioactive properties from the methanolic extract of the red seaweed Gracilaria damaecornis were evaluated. It was collected in Punta Arenas, Araya Peninsula, Sucre State, Venezuela. They were washed, dried in the shade at room temperature and ground, then macerated with methanol. The methanolic extract was obtained by reduced pressure. The antibacterial activity of the extract was evaluated by the agar diffusion method by the appearance of inhibition halos against certified Gram-positive and Gram-negative bacteria. Lethal activity was assessed against Artemia salina by quantification of the median lethal concentration (LC50). The LC50 value was 300.23 μg/ml showing moderate lethality against A. salina (LC50 ≤ 1000 μg/ml). Weak antibacterial activity was found against Gram (-) Escherichia coli and Gram (+) Bacillus cereus bacterial strains. The results obtained indicate that G. damaecornis is possibly a promising source of bioactive metabolites with potential application in the pharmaceutical industry.
