Metabolic Profiling and Antibacterial Activity of Carissa opaca Leaf Extracts: Bridging Experimental and...

This study investigated the antibacterial mechanisms of Carissa opaca Stapf ex Haines leaf extracts using in vitro assays and computational approaches. Phytochemical screening confirmed flavonoids, phenolics, terpenoids, saponins, and tannins, with methanolic extract showing the richest profile. Liquid chromatography-mass spectrometry (LC-MS) analysis identified scopoletin, carissone, nortrachelogenin, and evomonoside. Among the tested extracts, methanolic and ethyl acetate fractions showed the strongest antibacterial activity, producing inhibition zones of 14.2 ± 0.2 to 23.4 ± 0.5 mm against Klebsiella pneumoniae, Staphylococcus aureus, Salmonella typhi, Aeromonas sobria, and Bacillus cereus. Molecular docking revealed strong interactions of bioactive compounds with bacterial targets. Scopoletin exhibited the highest docking score (-8.43 kcal/mol) against penicillin-binding protein 2a (PBP2a), forming hydrogen bonds with Arg241, Arg234, Thr288, and His273. Molecular dynamics simulation (100 ns) confirmed the stability of the PBP-scopoletin complex with an average root mean square deviation (RMSD) of 2.32 Å and radius of gyration (Rg) (30.4 Å), indicating structural compactness. The GyrB-carissone complex also remained stable but showed slightly higher RMSD (3.71 Å) and Rg (33.4 Å). Overall, the combined in vitro and in silico findings highlight C. opaca leaf extracts, especially methanolic and ethyl acetate fractions, as sources of potent antibacterial agents. Scopoletin and carissone emerge as promising candidates for plant-derived antibacterial drug development.