Abstract The leaves extracts of Cassia sieberiana D.C. were screened for cytotoxicity using Brine Shrimp Test (BST) and antimicrobial bioassay against Staphylococcus aureus, Salmonella typhi and Escherichia coli using crude ethanol extract, Chloroform soluble fraction, aqueous soluble fraction, ethyl acetate soluble fraction, methanol soluble fraction and n-hexane soluble fraction. The Ethyl acetate fraction obtained proved to be most active in inducing complete lethality at minimum doses in BST and also active on Salmonella typhi. The Bioactivity result was used to guide the column chromatography, which led to the isolation of pure compound CSB-8, which was found active in the BST with LC50 value of 34(722-182) µg/ml and showed remarkable activity on Salmonella typhi (zone of inhibition 25mm) at 10,000 µg/ml. The 1H-NMR, 13C NMR, FTIR and GC-MS spectra of the compound suggested the proposed structure to be 2-pentadecanone.
Keywords Brine shrimp, Cassia sieberiana D.C., Antimicrobial bioassay.