Phytochemical screening and antibacterial activity of Azadiracta indica stem and leaf extracts on Esherichia coli and Staphylococcus aureus isolated from spoiled cabbage

Abstract

The study was aimed at determining the antibacterial activity of stem bark and leaf extracts of Azadirachta indica on laboratory isolates of Escherichia coli and Staphylococcus aureus obtained from spoiled cabbage. The phytochemical constituents of the extracts were screened. The aqueous and methanol extracts from the leaves and stem bark of the plant were then tested using agar well diffusion method for their antibacterial activity against laboratory isolates of Escherichia coli and Staphylococcus aureus obtained from spoiled cabbage. The result showed that the extracts were active against the microorganisms tested. The methanolic extract of stem bark showed the highest zones of inhibition against tested organisms (average of 17.25 mm) compared to the aqueous extract (average of 15.81 mm). Statistical analysis of the result shows that the extracts demonstrated high antibacterial activity against the isolates tested with the average zone of inhibition of 15.75 mm and 17.31 mm for E. coli and Staphylococcus aureus respectively. The Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) of the extracts ranged between 6.25 – 25 mg/ml. Preliminary phytochemical analysis showed that both stem bark and leaf extracts contain alkaloid, tannin, anthraquinone, flavonoid, phenols and terpenoid. The extracts of the plant demonstrated antibacterial activity due to presence of phytochemical constituents hence, the application of the decoction of leaf and stem bark of the plant in ethnomedicine is justified.

Keywords:  Azadirachta indica; phytochemical; well diffusion; antibacterial activity; Escherichia coli and Staphylococcus aureus