RESUMEN
Crossopteryx febrifuga is one of the useful plants used in Hausa traditional medicine in North Western Nigeria. It belongs to the family Rubiaceae. The phytochemical studies of the root bark of the plant was carried out using standard procedure. The was found tocontain: steroids, flavonoids, terpenoids, anthraquinones, cardiac glycosides, tannins, alkaloids and saponnins. The antimicrobial activity screening was carried out using both bacterial and fungal strains. The bacterial strains include: Pseudomonas aeruginosa, Staphylococcus aureus, Eschericia coli. The fungal strains Include: Aspergillus fumigatus, Candida albicans, Aspergillus flavus and Aspergillus niger. In general, the extract showed considerable activity on the bacterial species. It inhibited the growth of both gram positive and gram negative microorganism with zones of inhibition ranging from 7- 23 mm at concentrations of 50 μg/ml, 100 μg/ml and 200 μg/ml. The plant extract did not show significant activity on fungal strains. It inhibited the growth of Aspergillus fumigatus at 400 μg/ml and 500 μg/ml which produced zones of inhibition of 8 mm and 12 mm respectively at the stated concentration. It can be concluded that the activity showed by the methanolic extract of the plant is as a result of the phytochemicals present in the plant.