Phytochemical compounds and antimicrobial activity of three medicinal plants (Alchornea hirtella, Morinda geminata and Craterispermum laurinum) from Sierra Leone

Abstract

Petroleum ether, acetone, ethanolic and aqueous crude extracts of various plant organs of Alchornea hirtella, Morinda geminata and Craterispermum laurinum used in Sierra Leone exhibited variable degree of antimicrobial activity against four bacterial species. Compared with the standard drug ciprofloxacin, the extracts exhibited low to moderate antibacterial activity. Generally, the tested microorganisms were resistant to the petroleum ether and acetone extracts. The aqueous extract of the stem bark of M. geminata was sensitive to Streptococcus pyogenes (61% inhibition) and leaf extract of A. hirtella inhibited the growth of Proteus vulgaris (56%). Ethanolic crude extract of the stem bark of C. laurinum and M. geminata were particularly sensitive to S. pyogenes; moderate activity was also demonstrated by the stem bark of C. laurinum against Escherichia coli. MIC values indicated that the ethanolic extract showed significant microbiostatic action against S. pyogenes and Staphylococcus aureus (MIC 0.8 -2 mg/ml), whereas the other strains were more resistant (MIC >2 mg/ml). Phytochemical evaluation revealed moderate to high contents of flavonoids, alkaloid and saponins in the ethanolic extract.