Antioxidant and antibacterial activities in 21 species of Indonesian sea cucumbers

Sea cucumbers are marine organisms with uses in food, cosmetics, and medicine. This study aimed to identify Indonesian sea cucumbers with high antioxidant and antibacterial activities. Twenty-one sea cucumber species were used for this study. Antioxidant capacity was evaluated using the 2,2-diphenyl-β-picrylhydrazine assay. Antibacterial activity was assessed using the disk diffusion assay, whereas the resazurin-based assay was employed to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Volatile compounds possibly related to the biological activity of sea cucumbers were analyzed via gas chromatography–mass spectrometry (GC–MS). Holothuria atra had the strongest antioxidant capacity (IC50 = 14.22 ± 0.87 µg µL−1). Stichopus vastus displayed the best antibacterial activity against Staphylococcus aureus, whereas Stichopus ocellatus extract was most potent against Vibrio cholerae. Holothuria albiventer, which controlled Bacillus subtilis most effectively while also being active against S. aureus and V. cholerae, was the optimal antimicrobial species. H. albiventer and Actinopyga echinites inhibited B. subtilis growth at 12.5 µg µL−1. The MBC tests indicated that the antibacterial activities of sea cucumbers at the MIC were bacteriostatic, rather than bactericidal, in nature. GC–MS analysis uncovered long-chain fatty acids that might be associated with the antibacterial activities of sea cucumbers.