Comparative study of the in vitro phytochemicals and antimicrobial potential of six medicinal plants [version 1; peer review: 1 approved with reservations, 2 not approved]

Background: This study sought to investigate the antimicrobial activity of six plants used in traditional medicine in Africa. Methods: The antimicrobial activity of the six medicinal plant extracts (aqueous and ethanol) were evaluated against Proteus mirabilis (ATCC 21784), Pseudomonas aeruginosa (ATCC27856) were Aspergillus fumigatus using the agar-well diffusion protocol. The activities of these extracts were compared with the positive controls chloramphenicol and griseofulvin. Similarly, the phytochemicals from the extracts were qualitatively assayed and their percentage yield calculated by standard methods. Results: The bacterial organisms used, P. mirabilis and P. aeruginosa, were slightly-to-highly susceptible to aqueous and ethanolic extracts from the various test plants, while A. fumigatus was insensitive to the treatments. The ethanolic extracts of the sampled plants showed superior inhibitory performance on the target bacteria to the aqueous extracts. Aqueous and ethanolic extracts of Aframomum melegueta, Moringa oleifera and Cola nitida showed inhibitory consistency against the target bacteria. Superior inhibitory activity was observed for ethanol extracts of A. melegueta seed and M. oleifera pod against P. mirabilis and P. aeruginosa. Variations in phytochemicals were noticed across solvents and plant parts for all plants. Phenols were detected in the aqueous and ethanolic extracts of C. nitida and Cola acuminate, but relatively appeared denser in extracts of A. melegueta seed and Chrysophyllum albidium fruits. The extracts of C. nitida, C. acuminate and A. melegueta tested positive for the presence of flavonoids, which were undetected in C. albidium and M. oleifera seed and pod extracts. None of the extracts showed the presence of every phytochemical assayed during the study. Open Peer Review