Phytochemical and Antibacterial Activity Screening of Neem (Azadirachta indica) Bark Extracts from Sokoto State

The increasing prevalence of antimicrobial resistance globally has intensified efforts to identify natural product-derived alternatives to synthetic antibiotics. Azadirachta indica, commonly known as neem, has been widely used in traditional medicine across North West Nigeria for the management of infectious diseases. This study investigated the phytochemical composition and antibacterial activity of bark extracts of Azadirachta indica collected from Sokoto State. The bark was extracted sequentially using petroleum ether, ethyl acetate, methanol, and aqueous solvents. Standard qualitative phytochemical tests were performed on all extracts. Antibacterial activity was evaluated by the agar well diffusion method against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae. Minimum inhibitory concentration values were determined by the broth microdilution method. Phytochemical screening revealed the presence of alkaloids, flavonoids, tannins, saponins, terpenoids, and phenolic compounds in the methanol and aqueous extracts. The methanol extract demonstrated the broadest and most potent antibacterial activity, with inhibition zones ranging from 14 mm to 26 mm. Minimum inhibitory concentrations ranged from 3.13 to 12.5 mg/mL. Staphylococcus aureus showed the greatest susceptibility. Petroleum ether extract showed the lowest activity. The presence of alkaloids and tannins is proposed as a key contributor to the observed antibacterial effects. These findings validate the traditional use of neem bark in managing infections in Sokoto communities and support further bioassay-guided fractionation to identify and characterise active compounds.

Keywords: Azadirachta indica, phytochemistry, antibacterial activity, neem bark, Sokoto State