Antimicrobial evaluation of the methanol bark extracts of Plumbago dawei Rolfe, a local species used by the Samburu community, Wamba, Samburu District, Kenya for the treatment of diarrheal ailments
Omwenga, Eric O.
Okemo, P. O.
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Aims: The Samburu are a marginalized nomadic people in Kenya who have no access to conventional medical services thus they mainly depend on the medicinal plants for most of their medicare. Antimicrobial activity of the commonly used medicinal plant (Plumbago dawei Rolfe.) by the Samburu community was investigated to verify claims by locals of its medicinal properties. Methodology and results: The antimicrobial bioassays of the methanol extracts of P. dawei Rolfe was carried out by the disc diffusion method against Staphylococcus aureus ATCC 20591, Bacillus subtilis local isolate, Salmonella typhi ATCC 2202, Escherichia coli STD-25922 and Pseudomonas aeruginosa ATCC 25852. By use of the micro dilution method MICs and MBCs were also determined. Preliminary phytochemical screening was done on the extracts. The methanol extracts were highly active against all the test strains. The inhibitory zones ranged from 16-25.66 mm. The zones of inhibition were not significantly different except for the E. coli (16.33 mm) at p< 0.05. The extract showed strong MIC and MBC against S. typhi, S. aureus, E. coli and P. aeruginosa (MIC = 9.38 mg/mL and MBC = 9.38mg/mL). Thus the extract was more of bactericidal than bacteriostatic in most test strains. Preliminary phytochemistry revealed presence of flavonoids, tannins and cardiac glycosides. Conclusion significance and impact of study: The data suggests that methanolic extracts of P. dawei could be a rich source of antimicrobial agents. These results give scientific backing for the use of the P. dawei Rolfe, barks by the Samburu in the treatment of conditions associated with diarrhea and other associated infections caused by the test organisms. Keywords: diarrhea, medicinal plants, phytochemicals, antimicrobial activity