Antibacterial activity and phytochemical constituents of African birch (Anogeissus leiocarpus) stem bark extracts

Abstract

The genus Anogeissus (Combretaceae) is widely distributed in most tropical and subtropical countries of the world and has long been used in traditional medicine to treat a broad spectrum of disorders. The stem-bark powder of the plant was
extracted with butanol, hexane and water using percolation and soxhlet extraction methods. The extract fractions were screened for the presence and estimation of secondary metabolites using standard procedures. They were further tested for
antibacterial activity against clinical bacterial isolates of respiratory tract infections including Klebsiella pneumoniae, Klebsiella oxytoca, Klebsiella ozaenae, Escherichia coli and Pantoea agglomerans using disc diffusion and Epsilometer test (E- test)
techniques. The results of phytochemical screening indicated the presence of secondary metabolites including alkaloids, cardiac glycosides, reducing sugars, tannins, saponins, flavonoids, amino acids, anthraquinones, carbohydrates, steroids, triterpenes, monosaccharides and glycosides in the fractions of the extract. Bioassay test results showed that Klebsiella spp., P. agglomerans and E. coli were sensitive to aqueous and butanol extract fractions of the plant with highest sensitivity to aqueous fraction against E. coli (17-23 mm) using disc diffusion test and also having MIC and MBC values of 100 and 200mg/ml, respectively. The plant extract fractions were found to show inhibitory activity against the test isolates which may be related to the presence of secondary metabolites, some of which are reported to be responsible for antimicrobial properties. The results suggest that A.leiocarpus stem bark has the potential for the production of drugs against resistant bacteria.