Efficacy of Selected Medicinal Plants from Eastern Kenya against Aspergillus flavus

Abstract

Aflatoxins are a major problem in Eastern Province of Kenya and Aspergillus flavus has been associated with frequent outbreaks of aflatoxicoses in this region. This study evaluated the efficacy of 15 selected medicinal plants from Eastern Kenya against A. flavus. Different concentrations of 1000mg/ml, 750mg/ml and 400mg/ml using Agar Well Diffusion Method were used. Plants found to have inhibition zones of more than 10mm at 400mg/ml had their bark further assayed for antifungal activity. Both the leaf and bark extracts that were found to be effective were assayed for minimum inhibition concentrations (MIC) and minimum fungicidal concentrations (MFC) using Sabouraund Dextrose broth (SDB) micro-dilution method. The methanolic leaf and bark extracts of the fifteen plants assayed displayed concentration depended antifungal activities that was comparable to that of the reference drug Miconazole at 10mg/ml. Leaf extracts showed better antifungal activity than the bark extracts. For instance, Boscia coriacea (mean 17.40mm) had the highest zone of inhibition followed by Zanthoxylem chalybeum (mean 17.20mm). For the bark extracts, Croton megalocarpus (mean 15.0mm) recorded significantly high antifungal activity while Tithonia diversfolia (mean 13.0mm) had the lowest at 400mg/ml. Senna siamea had the lowest MIC and MFC of 6.25mg/ml and 12.5mg/ml respectively. The preliminary phytochemical analysis of the 15 effective medicinal plants revealed the presence of bioactive compounds that included tannins, saponins, flavonoids, terpenoids, cardiac glycosides and alkaloids. The results obtained from the study could be used as a viable management strategy against A. flavus and aflatoxins in the region so as to ensure low mycotoxin exposure as well as low environmental pollution.