Avaliação do potencial antibacteriano e da citotoxicidade do extrato orgânico da alga marinha Dictyota Dichotoma

Abstract

The marine environment is a rich ecosystem of organisms that produce bioactive compounds of biotechnological interest, extensively studied for their antiviral, antioxidant, antitumor, antifungal, anti-inflammatory, and antibacterial properties. The rise of multidrug-resistant bacteria due to the improper use of antibiotics highlights the importance of bioprospecting in the search for new molecules with antibacterial activity. This study investigated the antibacterial activity of the brown algae Dictyota dichotoma extract against strains of Escherichia coli, Staphylococcus aureus, and S. epidermidis. The seaweed was collected from the coast of Ceará and subjected to organic extraction using hexane, ethyl acetate, isopropanol, chloroform, acetone, acetonitrile, and methanol. For extract preparation, the seaweed was macerated with liquid nitrogen, followed by organic extraction in a 1:10 (weight/volume) ratio. Cytotoxicity was tested using the Artemia salina assay, and the extract showed no toxicity at concentrations ranging from 0.625 mg/mL to 5 mg/mL, suggesting its safety for future pharmacological tests. The antibiotic susceptibility test was conducted using the disk diffusion method, measuring inhibition zones. Results indicated that the extract obtained with acetonitrile was the most effective among the tested solvents, particularly against Gram-positive bacteria. The inhibition zones ranged from 7.5 mm to 8.5 mm for S. aureus and from 7.2 mm to 9 mm for S. epidermidis. The thermal stability evaluation of the extract revealed that antibacterial activity was maintained even after exposure to high temperatures, indicating the thermal resistance of the active compounds.