Phytochemical screening and antibacterial activity of Aspilia africana on some gastrointestinal tract pathogens

The main aim of this study was to determine the phytochemical constituents and antibacterial activities of the leaf extracts of A. africana. The powdered leaf of A. africana was extracted using 70% methanol and partitioned into n-hexane, chloroform, ethyl acetate and aqueous methanol fractions. The extract and fractions were phytochemically screened and agar well dilution technique was used to evaluate the antibacterial activity against some gastrointestinal tract pathogens (Escherichia coli, Staphylococcus aureus, Shigella dysentriae, Salmonella typhi, Salmonella paratyphi A, Salmonella paratyphi B and Salmonella paratyphi C). The phytochemical analysis of A. africana showed the presence of alkaloids, terpenoids, tannins, flavonoids, anthraquinones and saponins  in the methanol extract but varied across the fractions. The methanol extract and fractions inhibited the growth of gastrointestinal tract pathogens but their effectiveness varied with the concentrations. The methanol crude extract showed the best antibacterial activity with zone of inhibition ranging from 15-18 mm followed by aqueous soluble methanol fraction (10-15 mm) and ethylacetaate fraction (9-13 mm) respectively. The n-hexane and chloroform fraction showed no activity. Generally, the diameter zone of inhibition increased with increased extract concentrations. The antibacterial activity of the various extracts of the leaf was comparable to the reference antibiotics, though the antibiotics showed better inhibitory property (p<0.05) in some cases on the test isolates than the leaf extracts. The study showed that the leaves of A. africana possessed inhibitory properties due to the detected phytochemicals, thus validates the traditional uses of the plant for the treatment of gastrointestinal tract infections.