Abstract
Alkaloids were separated from black seed by using two type of solvents; ethanol and chloroform, we obtained two fractions of alkaloid (A1 and A2). Separated fractions were tested in different concentrations 50, 75, 100, 125 and 150 mg/ml against four types of bacteria
( Staphylococcus aureus , Bacillus cereus, E. coli and Pseudomonas spp.). The results showed that both fractions of alkaloid have antibacterial activity against tested bacteria but the effect of A1 was more than A2 and Gram positive bacteria were more sensitive than Gram-negative bacteria, the inhibition zone increased by increasing concentration of alkaloid in all tested bacteria.