No abstract

The isolation of secondary metabolites of seaweed Halimeda gracilis was conducted. Isolation begins with 2 kg macerated dried powder Halimeda gracillis in 8 L of n-hexane solvent followed by ethyl acetate and methanol for 3 days. The solvent was filtered and followed by evaporation. Separation and purification of the isolated compounds were done by using chromatography technique. Antibacterial activity was tested by the disc diffusion method with the bacteria E. coli, S. disentriae, and B. subtilis. Isolated compounds are in the form of white crystals. Based on the spectroscopy analysis data of UV, IR, 1H-NMR, 13C-NMR, HMQC, HMBC, and COSY, the pure compounds isolated are β-sitosterol from n-hexane extract and oleic acid from ethyl acetate extract. Isolated compounds and n-hexane extracts showed non antibacterial active, while the ethyl acetate extract showed weak antibacterial active on three test bacteria at a concentration of 200,000 ppm with clear zones of 9.47; 11.09; and 8.84 mm.