Antibacterial Activity, Phytochemical Screening, and GC MS Profiling of Annona senegalensis Leaf and Stem Bark Extracts Against Selected Bacterial Pathogens
Aisha Esther Ibrahim *
Department of Biological Sciences, Bingham University, Karu, Nasarawa State, Nigeria.
Danjuma Bulus
Department of Pharmaceutical Sciences, Bingham University, Karu, Nasarawa State, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Background: Antimicrobial resistance among bacterial pathogens continues to pose a serious global public health challenge, limiting the effectiveness of conventional antibiotics and necessitating the exploration of alternative therapeutic agents, including medicinal plants with documented antibacterial potential such as Annona senegalensis.
Aims: The study aims to investigate the antibacterial activity of Annona senegalensis leaf and stem‑bark extracts against selected bacterial pathogens and to characterise the phytochemical constituents and bioactive compounds responsible for the observed activity.
Study Design: Experimental laboratory study.
Place and Duration of Study: Department of Biological Sciences, Bingham University, Karu, Nasarawa State, Nigeria, between January and June 2025.
Methodology: Fresh leaves and stem‑barks of A. senegalensis were collected from Nasarawa State, Nigeria, and extracted sequentially with hexane, ethyl acetate, methanol, and hot water. Qualitative and quantitative phytochemical screening was performed using standard methods. Antibacterial activity was evaluated by disc diffusion at five concentrations (100, 50, 25, 12.5, 6.25 mg/mL) and broth microdilution (MIC/MBC) against standard strains of Streptococcus pneumoniae, Klebsiella pneumoniae, and Pseudomonas aeruginosa obtained from the National Veterinary Research Institute (NVIR), Vom, Plateau State, Nigeria. The two most active extracts were analysed by GC‑MS.
Results: Methanol stem‑bark extract (ASSM) gave the highest inhibition zone against S. pneumoniae (21.67 ± 0.58 mm at 100 mg/mL) and the lowest MIC (1.56 mg/mL). Methanol leaf extract (ASLM) also showed activity (MIC 1.56 mg/mL). Water and ethyl acetate extracts were considerably weaker. GC‑MS of the leaf hexane extract (ASLH) revealed phthalic acid ester (21.80%), phytol (16.50%), and sesquiterpenes; the stem‑bark methanol extract (ASSM) contained amide derivatives (1.49%), α‑acetobutyrolactone (1.28%), and an alkaloid‑related compound (1.21%). The MIC of erythromycin (positive control) was 0.78 mg/mL for all isolates.
Conclusion: Methanol extracts of A. senegalensis stem‑bark and leaf display significant antibacterial activity, attributable to high flavonoid content and identified bioactive compounds such as phytol and phthalic acid derivatives. These extracts merit further fractionation and toxicity assessment.
Keywords: Annona senegalensis, antibacterial, phytochemicals, GC MS, minimum inhibitory concentration.