Antibacterial Activities and Time‐Kill Analysis of Leaf Extracts of <i>Combretum adenogonium</i> Steud. Ex A. Rich In Vitro

Combretum adenogonium Steud. Ex A. Rich is a shrub tree native to tropical Africa. Its various parts are used in traditional medicine to treat both infectious and noninfectious diseases. This study investigated the activities and the killing rate of the plant leaf extracted with aqueous and ethanol (70% v / v ) against Staphylococcus aureus (American Type Culture Collection (ATCC) 29213), Staphylococcus epidermidis (ATCC 14990), Enterococcus faecalis (ATCC 29212), Pseudomonas aeruginosa (Deutsche Sammlung von Mikroorganismen und Zellkulturen (DSM) 1117), Escherichia coli (DSM 25944), and Salmonella typhi (ATCC 6539). The synergistic effect of each extract in combination with the standard antibiotics, ampicillin, ciprofloxacin, chloramphenicol, and tetracycline, was also investigated in vitro. It was revealed that both extracts were active against all test bacteria, with a mean zone of growth inhibition (ZoI) ranging from 23.50 ± 0.50 to 11.00 ± 0.00 mm at a concentration of 100 mg/mL. The mean ZoI of the ethanol extract (100 mg/mL) against E. faecalis (23.50 ± 0.50 mm) was significantly ( p ≤ 0.05) higher when compared with tetracycline (64 μ g/mL) (18.67 ± 0.29 mm). The minimum inhibitory concentrations of the extracts were between 0.39 and 12.50 mg/mL, while the minimum bactericidal concentrations ranged from 0.78 to &gt; 25 mg/mL. Time‐kill kinetics analysis revealed that both extracts were bacteriostatic against all Gram‐negative bacteria. The extract–antibiotic combinations resulted in synergy, additive, or indifferent outcomes, with none resulting in an antagonistic effect. The findings of the current study confirm the relevance of Combretum adenogonium in traditional medicine for the treatment of infections. For the first time, the time‐kill kinetics analysis and the interaction between the extracts of C. adenogonium in combination with some commonly used antibiotics against bacteria have been established. The activity could be attributed to the presence of saponins, phenolic compounds and tannins, flavonoids, phytosterols, and terpenes which were detected in the extracts by phytochemical screening.