Phytochemical Screening and Antibacterial Activity of Vernonia amygdalina (Bitter Leaf) Extracts from Taraba State

Vernonia amygdalina is one of the most widely used medicinal plants in Nigeria, consumed both as a food vegetable and as a remedy for a range of ailments including malaria, fever, and gastrointestinal infections. This study evaluates the phytochemical content and antibacterial activity of methanol, ethanol, and aqueous leaf extracts of Vernonia amygdalina harvested from Jalingo, Taraba State. Fresh leaves were authenticated by a plant taxonomist, dried, powdered, and extracted by cold maceration in each solvent for seventy-two hours. Phytochemical screening followed standard Harborne methods. Antibacterial activity was tested against Staphylococcus aureus, Bacillus cereus, Salmonella typhi, Escherichia coli, and Shigella dysenteriae using the disc diffusion assay, with MIC and minimum bactericidal concentration (MBC) determined by serial broth dilution. Phytochemical analysis confirmed the presence of alkaloids, tannins, sesquiterpene lactones, saponins, phenols, and flavonoids. The methanolic extract produced the largest inhibition zones against Salmonella typhi (18 mm) and Staphylococcus aureus (16 mm). The MIC for the methanol extract against Salmonella typhi was 12.5 milligrams per millilitre. Gram-negative organisms were generally less susceptible than gram-positive isolates. Sesquiterpene lactones, particularly vernodalin and vernolide, are implicated as the primary antibacterial compounds. The study provides biochemical justification for the use of Vernonia amygdalina in managing bacterial infections in rural communities in Taraba State. Keywords: Vernonia amygdalina, bitter leaf, antibacterial, phytochemicals, Taraba State.