Phytochemical screening and studies on antibacterial activity of leave extract of Stereospermum kunthianum -a plant widely used by traditional medical practitioners in Northern Nigeria, were carried out on Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella spp, Salmonella spp and Aeromonas hydrophila using agar well diffusion technique. Preliminary phytochemical screening revealed the presence of sterols, coumarins, higher fatty acids and the absence of flavones aglycone and alkaloids in the leave extract. The activity of the extract was more potent at 30 mgml-1 with zone of growth inhibition against S. aureus (35 mm), Klebsiella spp (28 mm) and A. hydrophila (28 mm). The least activity was on P. aeruginosa (9 mm). The minimum inhibitory concentration (MIC) of the extract was 2.09 mgml-1 on Klebsiella spp and S. aureus while 4.17 mgml-1 on Salmonella spp and A. hydrophila. Similarly, the minimal bactericidal concentration (MBC) was 2.09
mgml-1 on S. aureus and 4.17 mgml-1 on Klebsiella spp. however, higher MIC and MBC of 16.67 mgml-1 were observed on P. aeruginosa. The spectra of activities displayed by the extract can be attributed to the presence of these phytochemicals which signifies the potential of S. Kunthianum as a source of therapeutic agents. This therefore, supports the traditional medicinal use of S. kunthianum in Zaria, Nigeria.
KEYWORDS: Stereospermum kunthianum, phytochemical, antibacterial activity, Bignoniaceae