Antibacterial Activity and Identification of Active Compounds of Seaweed Extract Sargassum sp., Halimeda opuntia and Halymenia sp. from Lae-Lae Island of South Sulawesi

In addition to containing primary metabolites, seaweed also contains secondary metabolites in the form of active compounds that function as antimicrobial and anticancer. Some species of seaweed include brown seaweed from the genus of Sargassum, green seaweed from the genus of Halimeda and red seaweed from the genus of Halymenia. The waters around Makassar City found species of Sargassum sp., Halimeda opuntia and Halymenia sp., which is abundant especially on Lae-Lae Island, but studies on its potential bioactivity are still very limited. This research aims to determine the bioactivity and identification of the active compound groups of the extracts of Sargassum sp., Halimeda opuntia and Halymenia sp. The research was carried out in December – April 2021. Samples were extracted using the meseration method. Antibacterial activity test used agar diffusion method and phytochemical test used Thin Layer Chromatography (TLC). The yield of methanol extract and seaweed hexane of Sargassum sp. respectively 2.4 and 2.3% and Halimeda opuntia of 0.53 and 1.15% and Halymenia sp. of 2.42 and 0.89%. The six seaweed extracts had no activity against E. coli bacteria. Hexane extract of Sargassum sp. had the highest activity against the bacteria of S. typhi with an average diameter of 25.67 mm and the highest level against the bacteria of A. hydrophila with an average diameter of 18.2 mm with methanol as solvent. The same activity was shown by methanol extracts of Sargassum sp. and Halymenia sp. against the bacteria of V. harveyi with an average zone diameter of 18.04 mm. However, only the methanol extract of Halimeda opuntia had activity against the bacteria of P. aeruginosa with an average diameter of 8.63 mm. An important finding that was found from the results of this research was the extract of Sargassum sp. showed the highest activity against S. typhi, A. hydrophila and V. harveyi with a higher diameter inhibition zone than the commercial antibiotic activity of ciprofloxacin as a positive comparison. This shows that the extract of Sargassum sp. has a great potential as a source of new antibiotics, especially against S. typhi. The extracts of methanol and hexane of Halimeda opuntia and methanol of Sargassum sp. contains 5 active compounds namely, alkaloids, flavonoids, tannins, triterpenonids and saponins. While the seaweed hexane extracts of Sargassum sp., only contains 3 active compounds namely, alkaloids, tannins and saponins. The methanol extracts of Halimeda opuntia contains 4 active compounds namely, flavonoids, tannins, triterpenonids and saponins, while the hexane extracts contain alkalaoids, flavonoids, tannins and saponins.