The association between antifungal activity and antiparasitic activity of plant extracts against helminths

Haemonchus contortus is globally the most important helminth that causes tremendous losses in small animal production. Treatment cost with anthelmintics to manage infestations was more than $175 million in South Africa, Kenya and India in 2004 [1]. Many poor farmers cannot afford the cost of the anthelmintics. The situation is aggravated by the strong development of resistance by the parasite against currently used anthelmintics. Plants have been used to treat helminth infections by rural farmers with some positive results. The isolation of anthelmintic compounds is challenging due to the demanding assays required for bioassay-guided fractionation. A class of the important anthelmintics the benzimidazoles have good antifungal activity [2]. We separated plant extracts into different fractions based on polarity and determined the activities. When the ethyl acetate fraction was omitted there was an excellent correlation between egg hatch assay and minimum inhibitory concentration (MIC) (R²= 0.9) and a good correlation between larval development and MIC, (R²= 0.6). We determined the anthelmintic activity of 13 tree leaf extracts with known antifungal activity. In many cases there appeared to be a good association between egg hatch assay and the larval development assay of H. contortus. When we analysed the data there was some correlation between the MIC of Cryptococcus neoformans and the egg hatch assay (R²= 0.15) and also between Aspergillus fumigatus and the egg hatch assay (R²= 0.15). The correlations between the MICs and the larval development was much lower (R²= 0.01). By deleting outliers the correlation was improved. We conclude that if the mechanism of antifungal activity is related to the anthelmintic activity it may be worthwhile to isolate antifungal compounds and then determine their anthelmintic activities.

References:

[1] Waller PJ, Chandrawathani P Trop Biomed 2005; 22: 131 – 137

[2] Adamu et al. 2012; 12: 213