Selective in vitro anthelmintic efficacy of Diospyros whyteana (Ebenaceae) active compounds derived using antifungal activity to guide fractionation

Nematodes are economically important parasites in livestock. Control of these infections relies mainly on synthetic anthelmintic drugs, against which development of resistance is a major problem. Many farmers, particularly in rural areas, use ethnoveterinary preparations comprising medicinal plants to combat endoparasitism. As anthelmintic assays are difficult and time-consuming, the aim of this study was to investigate if antifungal assays can be used as a model to isolate anthelmintic plant compounds, based on potential correlations in the two activities. In the anthelmintic egg hatch assay (EHA) and the larval development assay (LDA), the Diospyros whyteana acetone leaf extract had good activity with EC₅₀ values of 4.43 and 5.58 µg/ml respectively. The extract was active against Candida albicans with MIC of 40 µg/ml, and this organism was used as a model to isolate antifungal compounds from D. whyteana. Bioactivity of the fractions as well as cytotoxicity (IC₅₀, tested using Vero cells in the colorimetric MTT assay) was assessed during fractionation, which resulted in isolation of three active compounds. EC₅₀ values of the compounds ranged from 0.11 to 3.30 in the EHA and 1.5 to 4.35 in the LDA, with promising SI values above 28. The three compounds had the same MIC of 160 ug/ml against C. albicans. Results showed a good correlation between the EHA and LDA as well as good antifungal activities, indicating that the use of the antifungal assay assisted with the isolation of anthelmintic compounds. These compounds are being identified in current work.