Antimicrobial activity and cytotoxicity of selected medicinal plants found in Nandi County, Kenya

Abstract

Background: Medicinal plants are widely used by the local people to treat various human diseases cause by drug resistant microorganisms. For instance, Kigelia Africana fruits and barks are boiled in water and taken orally as a laxative in treating stomach ailments, Ekebergia capensis bark is boiled in water and use for the control of gonorrhea and tuberculosis while Fagaropsis angolensis stem bark is used to treat pneumonia, back ache and joins. The efficacy and safety of most of these plants has not been determined.

Objective: The present study seeks to determine antimicrobial activities and cytotoxicity of the selected medicinal plants indicated above, that are commonly used to treat infectious diseases.

Materials and Methods: Fresh plants were collected from the field; air dried ground and extracted using acetone and water. The extracts were screened for antibacterial and antifungal activities using Staphylococcus aureus, Methicillin resistant Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Shigella dysentriae, Candida albicans, Cryptococcus neoformans, Microsporum gypseum and Trychophyton mentagrophytes. The methods were disc diffusion and broth dilution methods while in vitro cytotoxicity test was carried out following a modified rapid calorimetric assay, using actively dividing sub-confluent Vero E6 cells.

Results: In disc diffusion assay, water extracts of E. capensis were the most active (14.7 mm) while those of Fagaropsis angolensis were the least (6.0 mm) against S. aureus. Acetone extracts of E. capensis and K. Africana had a Minimum Inhibitory Concentration of 3.125 mg/ml and 6.25 mg/ml respectively and were bactericidal. Cytotoxicity showed that K. africana was not cytotoxic against Vero cell lines while acetone extracts of E. capensis was moderately toxic with a CC ₅₀(µg/ml) of 12.5.

Conclusion: These results support the use of the plants in the traditional medicine as antimicrobials and they can be exploited for novel drugs.

Key words: Antimicrobial activity, cytotoxicity, Kigelia africana, Ekebergia capensis, Fagaropsis angolensis