Screening and Molecular Docking of Bioactive Metabolites of the Red Sea Sponge Callyspongia siphonella as Potential Antimicrobial Agents

Marine sponges create a wide range of bioactive secondary metabolites, as documented throughout the year. Several bioactive secondary metabolites were isolated from different members of Callyspongia siphonella species. This study aimed for isolation and structural elucidation of major metabolites in order to investigate their diverse bioactivities such as antimicrobial and anti-biofilm activities. Afterwards, a molecular docking study was conducted, searching for the possible mechanistic pathway of the most bioactive metabolites. Extraction, fractionation, and metabolomics analysis of different fractions was performed in order to obtain complete chemical profile. Moreover, in vitro assessment of different bioactivities was performed, using recent techniques. Additionally, purification, structural elucidation of high features using recent chromatographic and spectroscopic techniques was established. Finally, AutoDock Vina software was used for the Pharmacophore-based docking-based analysis. As a result, DCM (dichloromethane) fraction exerted the best antibacterial activity using disc diffusion method; particularly against S. aureus with an inhibition zone of 6.6 mm. Compound 11 displayed a considerable activity against both MRSA (Methicillin-resistant Staphyllococcus aureus) and Staphyllococcus aureus with inhibition ratios of 50.37 and 60.90%, respectively. Concerning anti-biofilm activity, compounds 1 and 2 displayed powerful activity with inhibition ratios ranging from 39.37% to 70.98%. Pharmacophore-based docking-based analysis suggested elongation factor G (EF-G) to be a probable target for compound 11 (siphonellinol C) that showed the best in vitro antibacterial activity, offering unexplored potential for new drugs and treatment candidates.