Phytochemical screening and elemental analysis was carried out on water and ethanol extracts of Cassia siberiana leaves. The antimicrobial activityy and minimum inhibitory concentrations (MIC) of the leaves extract were also studied. Preliminary phytochemical investigation revealed the presence of alkaloids, flavonoidss, anthraquinones, saponins, glycosides, tannins, carbohydrates and terpenes. Elemental analysis revealed the presence of calcium (Ca), phosphorus (P), Magnesium (Mg), Manganese (Mn), Iron (Fe), Copper (Cu) and Zinc (Zn). Manganese was present at the higher concentration of 9.50μg/g followed by Zinc 2.4μg/g. Antimicrobial studies showed that the ethanol extract had considerable activities and significant inhibition against staphylococcus aureus, streptococcus pyogen, salmonella typhi, shigella dysentery and Eschenchia coli. Ethanol extract had higher zone of inhibition (32mm) against salmonella typhi at (0.5μg/ml) with minimum inhibitory concentration (MIC) value of 4 x 102 μg/ml. The MIC ranges from 2 x 102 μg/ml to 5 x 104 μg/ml.
