In Vitro and In Silico Analysis for Antibacterial Activities of Various Extracts of Gracilaria salicornia (Rhodophyta) from Selayar Islands, Indonesia

This study aims to evaluate the toxicity, antibacterial activity, and chemical profiling of Gracilaria salicornia extract. The research stages included the extraction, bioactivity test, GC-MS, and docking analysis. The extraction of samples was carried out by gradient maceration. The toxicity of the extracts was analyzed using the BSLT method, and the antibacterial activity was analyzed by paper disc diffusion. The antibacterial activity showed better sensitivity against Escherichia coli than Staphylococcus aureus. The inhibition zone against E. coli ranged from 7.73-17.30 mm, while S. aureus ranged from 6.91-13.44 mm, and all of the extracts were toxic to Artemia salina Leach. The chloroform extract showed the highest activity with the clear zone diameter was 17.3±1.65 mm and 13.44 ± 0.04 mm to E. coli and S. aureus respectively. The presence of steroids, terpenoids, fatty acids, and alkane based on GC-MS and docking analysis were responsible for these activities. Molecular docking analysis showed that Cholest-5-en-3-ol and Cholesta-4,6-dien-3-ol showed better interactions than control with binding energy -9.99 and -9.67 kcal.mol-1 against 5BMM, -8.00 and -7.93 kcal.mol-1 against 3LPS respectively. Based on this data, it can be stated that G. salicornia extract is highly potential as the source of antibacterial compounds