Antibacterial potentials of selected drought resistant plants in University of Maiduguri campus: a study of Adansonia digitata, Balanites aegyptiaca, and Vachellia nilotica

Abstract

The rising burden of antibiotic-resistant infections and the continued relevance of plant-based medicine in developing regions have created an urgent need to explore underutilized medicinal flora. This study investigated the antibacterial activity of ethanol extracts prepared from the leaves, stembark, and roots of three drought-resistant plants — Adansonia digitata, Balanites aegyptiaca and Vachellia nilotica— collected from the University of Maiduguri campus, located in the semi-arid Sahel savanna zone of northeastern Nigeria. Plant materials were shade-dried, powdered, and extracted by cold maceration in ethanol for 72 hours. Antibacterial activity was evaluated using the disc diffusion (Kirby-Bauer) method against six American Type Culture Collection (ATCC) reference bacterial strains — Staphylococcus aureus, Bacillus subtilis, Streptococcus pyogenes, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae — with Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) determined by broth microdilution. Results revealed that stembark extracts consistently exhibited the strongest antibacterial activity across all three plants. Vachellia nilotica stembark produced the largest zones of inhibition (24.6–28.4 mm at 200 mg/mL), with MIC values as low as 62.5 µg/mL, nearly comparable to ciprofloxacin. Gram-positive bacteria were generally more susceptible than Gram-negative strains, with Pseudomonas aeruginosa showing the highest resistance. These findings demonstrate that drought-adapted plants from the Sahel region are promising sources of potent antibacterial compounds and warrant further phytochemical and pharmacological characterization.