Research Article published by European Journal of Medicinal Plants
Aims: To evaluate antibacterial activity from five selected medicinal plants namely Embelia
schimperi, Maerua decumbens, Ocimum gratissimum, Conyza floribunda and Plectranthus
barbatus used for the management of bacterial infections in Tanzania.
Study Design: In vitro antibacterial activity was carried out by using 96 well microplates method.
Place and Duration of Study: The samples were collected in three region of Tanzania namely
Kilimanjaro, Arusha and Dodoma. Extraction and antibacterial assay was conducted at School of
Life Sciences and Bioengineering, Nelson Mandela African Institution of Science and Technology,
Tanzania, between February and June 2015.
Methodology: Minimum Inhibitory Concentration (MIC) of plants extracts against the tested Gram
negative bacteria was determined by using 96 well microdilution methods.
Results: Plant extracts exhibited antibacterial activity with MIC range of 1.56 mg/mL to >25 mg/mL. About 36% (8) of extracts, out of 22 extracts demonstrated antibacterial activity with MIC of 1.56
mg/mL against K. oxytoca, P. aeruginosa, P. mirabilis, E. coli and S. typhii. The inter-species
activity comparison indicated that antibacterial activity of the evaluated plant species are in order of
Conzya floribunda ˃ Plectranthus barbatus > Maerua decumbens > Embelia schimperi and
Ocimum gratissimum. The Conyza floribunda extracts exhibited a narrow range antibacterial
activity (MIC of 1.56 to 6.25 mg/mL) compared to the rest of plant species in this study.
Conclusion: The highest inhibitory effects exhibited by C. floribunda root chloroform,
O. gratissimum leaf methanolic and O. gratissimum flower ethyl acetate extracts against at least
two bacteria strains validates the traditional uses of these plants for the management of infections
caused by Gram negative bacteria.