Anthelmintic screening of Zimbabwean plants traditionally used against schistosomiasis

Extracts of 23 plant species used popularly against schistosomiasis in Zimbabwe were screened for their anthelmintic effect. Schistosomules of the trematode Schistosoma mansoni and cysticercoids of the cestode Hymenolepis diminuta were studied in vitro. The material consisted of 58 plant extracts, of which 37 killed the newly excysted cysticercoids within an hour, when incubated in a culture medium. Lethal concentrations varied from 0.8 to 103 mg/ml. All plant extracts showed activity against the tapeworms after 24 h. Ten of the best extracts were also tested against schistosomules. Five of these extracts showed activity. Lethal concentrations varied from 0.6 to 33.8 mg/ml of dry plant material. Extracts of stem and root from Abrus precatorius (Fabaceae), of root bark and leaves from Ozoroa insignis (Anacardiaceae) and of root bark from Zizyphus mucronata (Rhamnaceae) gave the best results against tapeworms. The best results against schistosomules were obtained with stem and root extracts from Abrus precatorius (Fabaceae) and stem bark from Elephantorrhiza goetzei (Mimosaceae). Although the activity of root and root bark extracts commonly used in traditional medicine was verified in this study, our results showed that also extracts from leaf and stem can be effective anthelmintics.