PHYTOCHEMICAL AND ANTIBACTERIAL ACTIVITY OF VERNONIA AMYGDALINA LEAF EXTRACTS AGAINST SELECTED BACTERIAL PATHOGENS

This study investigated the antibacterial and antioxidant properties of Vernonia amygdalina (bitter leaf) extracts against selected bacterial pathogens. Three organisms—Staphylococcus aureus, Escherichia coli, and Klebsiella pneumoniae—were isolated and identified using cultural, morphological, and biochemical methods. The antibacterial activity of both aqueous and ethanol extracts of V. amygdalina was assessed using the agar well diffusion method at concentrations ranging from 12.5 to 200 mg/ml. Results showed that both extracts inhibited bacterial growth, but the ethanol extract exhibited stronger activity at all concentrations. The minimum inhibitory concentration (MIC) of the ethanol extract was 12.5 mg/ml for all isolates, while the aqueous extract required higher concentrations (25–50 mg/ml). Phytochemical screening revealed the presence of alkaloids, tannins, phenols, flavonoids, and saponins, with higher levels recorded in the ethanol extract. Quantitative analysis also confirmed greater amounts of phenols, tannins, flavonoids, alkaloids, and saponins in ethanol compared to aqueous extracts. Antioxidant assays indicated strong activity in both extracts, with ethanol extract (132.66 µg/ml) slightly higher than aqueous extract (128.62 µg/ml). Overall, the findings suggest that V. amygdalina possesses significant antibacterial and antioxidant activities, with ethanol serving as a more efficient solvent for extracting its bioactive compounds. These results support the traditional use of bitter leaf in managing infectious diseases and highlight its potential as a source of natural antimicrobial agents.