Isolation of the anti-bacterial vernodalin from traditionally used Vernonia colorata

Leaf extracts of Vernonia colorata were screened for anti-bacterial activity using the disc-diffusion assay. Micrococcus luteus, Klebsiella pneumoniae and Staphylococcus aureus were inhibited by ethyl acetate extracts, but not by hexane and water extracts. The ethyl acetate extract was fractionated by silica vacuum chromatography and a chromatron using hexane:ethyl acetate gradients. The presence of anti-bacterial activity was confirmed by bioautography. The major anti-bacterial compound in the ethyl acetate leaf extract was identified by NMR as vernodalin. The minimal inhibitory concentration of vernodalin against S. aureus was 100μg ml-1.