Phytochemical Profiling and In Vitro Antibacterial Activity of Leonotis ocymifolia (Burm. f.) and Laggera tomentosa (Sch. Bip. ex A. Rich) Leaf Extracts Against Clinically Relevant Human Pathogenic Bacteria

Background: Leonotis ocymifolia and Laggera tomentosa are traditionally used in Ethiopian folk medicine to treat various ailments. This study evaluated the phytochemical constituents and antibacterial activity of their leaf extracts against selected human pathogenic bacteria. Methods: Crude extracts were prepared using six solvents (chloroform, ethanol, methanol, hexane, ethyl acetate, and water) via maceration. Phytochemical screening employed standard procedures. Plant activity against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Streptococcus pneumoniae was assessed using disc diffusion (100 mg/mL), with MIC and MBC determinations. Results: L. ocymifolia contained flavonoids, tannins, alkaloids, and phenols; L. tomentosa additionally contained saponins. Chloroform extracts exhibited the highest activity, with inhibition zones of 20 ± 1 mm (L. ocymifolia against P. aeruginosa) and 20 ± 4.6 mm (L. tomentosa against P. aeruginosa). Water extracts showed minimal or no activity against several strains. MIC values ranged from 1.56–12.5 mg/mL (L. ocymifolia) and 3.13–6.25 mg/mL (L. tomentosa); MBC values ranged from 3.13–12.5 mg/mL and 3.13–6.25 mg/mL, respectively. Conclusion: Chloroform extracts of both plants demonstrated significant broad-spectrum antibacterial activity, validating their traditional use and highlighting their potential as sources of novel antibacterial agents.