In Vitro and In Silico Assessment of Brown Seaweed Sargassum wightii Metabolites Against Acinetobacter baumannii

Acinetobacter baumannii (A. baumannii) is a notorious nosocomial pathogen known for its ability to form biofilms, which contribute to its high resistance to conventional antibiotics and immune clearance. This study aimed to evaluate the antibiofilm activity of ethanolic extracts of Sargassum wightii against multidrug-resistant (MDR) A. baumannii and to identify potential bioactive compounds using gas chromatography–mass spectrometry (GC-MS) and molecular docking. The ethanolic extract exhibited minimum inhibitory concentration (MIC) values ranging from 70 to 100 µg/mL against A. baumannii. Moreover, the extract inhibited biofilm formation in a concentration-dependent manner, which was further confirmed by epifluorescence microscopy, revealing a marked reduction in biofilm biomass compared with the untreated control. GC-MS analysis of the ethanolic extract of S. wightii identified 10 major compounds. Molecular docking was performed to investigate the interaction of the identified bioactive compounds with the biofilm response regulator protein BfmR of A. baumannii. Among the identified compounds, three molecules (CAS No. 002302-12-7, 015120-94-2, and 146397-91-3) exhibited the highest binding affinity toward BfmR. Ligands CAS No. 002302-12-7 and CAS No. 146397-91-3 showed binding energies (∆Gbind) of −42.26 and −50.49 kcal/mol, respectively, while CAS No. 015120-94-2 achieved the lowest Glide score (−4.067 kcal/mol). These compounds demonstrated promising interactions with BfmR and may serve as a putative molecular target potentially associated with the observed antibiofilm activity in A. baumannii. Overall, the findings indicate that S. wightii possesses significant antibiofilm activity against A. baumannii, with its bioactive constituents exhibiting promising drug-likeness and pharmacokinetic properties, demanding further experimental validation.