Antimicrobial Efficacy of Ocimum gratissimum (Scent Leaf) against Enteric Bacteria Isolated in Benue State, Nigeria

Background: Ocimum gratissimum (scent leaf) is used in Nigerian traditional medicine for the management of infectious conditions. The activity of extracts from different plant parts against enteric bacteria isolated in Benue State was assessed. Aim: This investigation assessed the antibacterial potential of aqueous and methanolic extracts of O. gratissimum leaf, stem, and root against enteric pathogens. Methods: Leaves, stems, and roots were collected from Ogobia, Otukpo Local Government Area, Benue State, and authenticated (Voucher No. FULH/OAA/078). Qualitative phytochemical screening and gas chromatography–mass spectrometry (GC-MS) were conducted to identify active constituents. Antibacterial activity against clinical isolates of Escherichia coli, Salmonella spp., and Shigella spp. was evaluated by agar well diffusion, and the minimum inhibitory concentration (MIC) was determined by broth dilution. Results: Phytochemical analysis revealed tannins, saponins, alkaloids, terpenoids, reducing sugars, and fats/oils. Only the methanolic leaf extract exhibited activity, and exclusively against E. coli, with inhibition zones of 21 mm at 0.20 g/mL, 16 mm at 0.10 g/mL, 8 mm at 0.05 g/mL, and 3 mm at 0.025 g/mL. The MIC was 0.05 g/mL. All aqueous extracts, stem and root extracts, and Salmonella spp. and Shigella spp. showed no susceptibility. Conclusion: The methanolic leaf extract of O. gratissimum contains bioactive compounds with selective activity against E. coli. Isolation, characterization, and toxicity profiling of the active principles are recommended.