Preliminary phytochemical screening and antibacterial activity of Leonotis ocymifolia (Burm. f.) and Laggera tomentosa (Sch. Bip. ex A. Rich) leaf extracts against clinically relevant human pathogens

Leonotis ocymifolia and Laggera tomentosa are used in Ethiopian traditional medicine, yet scientific validation of their antibacterial properties is limited. This study investigates the phytochemical composition and antibacterial activity of leaf extracts from both species against clinically relevant pathogens. Crude extracts were prepared using six solvents across a polarity. Phytochemical screening was performed using standard qualitative tests, and antibacterial activity was evaluated via disc diffusion (100 mg/mL) and agar dilution methods to determine Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC). Chloroform extracts showed the highest activity, producing inhibition zones of 20 ± 1 mm against P. aeruginosa . Phytochemical screening revealed the presence of flavonoids, tannins, phenols, and alkaloids in organic fractions, with aqueous extracts showing limited metabolite diversity. MIC values ranged from 1.56 to 12.5 mg/mL, indicating weak to moderate antibacterial activity according to established classification criteria. MBC/MIC ratios ≤ 2 across most strains suggest bactericidal potential. While the crude extracts demonstrated relatively weak antibacterial activity (MIC > 1.0 mg/mL), the consistent bactericidal profile and superior efficacy of chloroform fractions warrant further investigation through bioassay-guided fractionation to isolate and concentrate the active compounds. These findings provide a preliminary scientific basis for the traditional use of these plants and highlight the need for comprehensive phytochemical characterization.