In-vitro antibacterial activity of methanolic extract of Eucalyptus tereticornis and Ruta chalepensis against selected pathogenic bacteria

The rise of antimicrobial resistance is a critical global threat to both human and animal health, intensifying the search for novel antibacterial compounds from medicinal plants to supplement or replace failing conventional drugs. This study evaluated the in-vitro antibacterial activity of methanolic extracts from Eucalyptus tereticornis and Ruta chalepensis against selected pathogenic bacteria. Methanolic extracts were prepared from the bark and leaves of E. tereticornis and the aerial parts of Ruta chalepensis . The antibacterial potential was tested against Escherichia coli (ATCC 25,922), Pseudomonas aeruginosa (ATCC 27,853), and Staphylococcus aureus (ATCC 25,923) using the disc diffusion method, while Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) were determined via the broth dilution assay. Qualitative phytochemical screening was also conducted to identify secondary metabolites. The extraction yields were 35.4% (leaf) and 29 % (bark) for E. tereticornis , and 20 % for R. chalepensis . Among the extracts, Ruta chalepensis exhibited the strongest antibacterial activity, particularly against S. aureus , with a mean zone of inhibition of 18.7 ± 0.7 mm and a notably low MIC of 1.95 mg/ml. Although all extracts demonstrated dose-dependent activity, Gram-positive S. aureus was found to be more susceptible than the Gram-negative strains. These findings demonstrate that R. chalepensis and E. tereticornis possess significant antibacterial properties against standard pathogenic strains, providing a scientific basis for their traditional use and highlighting their potential as sources for new antimicrobial agents.