Antibacterial and antibiofilm effects of invasive corals Tubastraea coccinea and Tubastraea tagusensis

This study evaluated the antibacterial and antibiofilm activities of methanolic extracts from the invasive corals Tubastraea coccinea and Tubastraea tagusensis and a synthesized alkaloid (APL01). The antibacterial activity was evaluated by macrodilution and microdilution methods using 16 bacterial strains. The antibiofilm activity was evaluated in Staphylococcus aureus in the biofilm inhibition assay. The cytotoxic potential was also analyzed in human carcinoma cell lines HEp-2 and Caco-2. All samples were capable of interfering with the growth of bacterial strains, highlighted by the methanolic extract of T. coccinea, which inhibited the growth of the Streptococcus pyogenes (8668) strain (IC50 = 66.31 µg mL−1). All samples were able to inhibit biofilm formation, with EC50 values for EbMTc, EbMTt, and APL01 being 414.1, 82.08, and 153.9 µg mL−1. Both extracts showed cytotoxic effects; the Caco-2 cell line was the most sensitive. The results were expressed as the selectivity index. The methanolic extracts of T. coccinea and T. tagusensis (EbMTc and EbMTt, respectively) presented antimicrobial potential, inhibiting the growth of the S. pyogenes (8668) strain. Both extracts and APL01 inhibited the formation of biofilms in S. aureus. EbMTc was the most promising sample for antimicrobial activity. The use of sun coral samples for antimicrobial activity in pharmacological research can be studied further.