In vitro nematocidal potential of hydro-ethanolic and aqueous extracts of Calotropis procera (Aiton) W.T. Aiton, 1811 (Apocynaceae) and Faidherbia albida (Delile) A. Chev., 1934 (Fabacae) against Onchocerca ochengi and Caenorhabditiselegans

Onchocerciasis caused by Onchocerca volvulus Leuckart, 1893 is the second-world infection responsible for human blindness. Except Ivermectin which has as targets the microfilariae of that parasite, specific treatment for this disease does not exist and in developing countries, medicinal plants seem to remedy that health problem. For that, aqueous and hydro-ethanolic leaf, bark, and root extracts of Calotropis procera and Faidherbia albida were evaluated in vitro, against the most popular bovine model, Onchocerca ochengi and the free-resistant nematode Caenorhabditis elegans. O. ochengi microfilariae and adults extracted from the bovine nodules and skins as well as the free strains of C. elegans were exposed to the various concentrations of the plant parts extracts and Ivermectin. In results, all the plant parts extracts were rich in tannins, saponins, alkaloids, flavonoids, phenols, coumarins, and glycosides. Phenols (175.45 ± 0.01 mg EGA/g DM), flavonoids (158.98 ± 0.05 mg EC/g DM), and tannins (89.98 ± 2.56 mg ETA/g DM) contents were high in the bark hydro-ethanolic extract of F. albida. The leaf hydro-ethanolic extract of F. albida induced high activity against O. ochengi microfilariae (CL(50) = 0.13 mg/mL). The bark hydro-ethanolic extract of F. albida was also the most effective on O. ochengi adults and particularly on female adults (CL(50) = 0.18 mg/mL). Against the parasite strain resistant to Ivermectin, F. albida leaf hydro-ethanolic extract appeared more active with CL(50) = 0.13 mg/mL. Similarly, the bark hydro-ethanolic extract of F. albida was the most potent on the wild strain of C. elegans. Thus, this study validates the use of these plants by traditional healers in the management of onchocerciasis and suggests a new source of isolation of the potential plant compounds against Onchocerca.