Cercaricidal activity of some essential oils of plants from Brazil.

Extended screening tests on the cercaricidal activity of various plants from northeast Brazil have shown that the extracts of the leaves and fruits of Piper marginatum, Protium heptaphyllum, and Capsicum annuum show a remarkable effect on the cercaria of Schistosoma mansoni. In the case of the oils of Piper marginatum and Capsicum annuum, 90--96% of the cercaria of Schistosoma mansoni were killed within 15 min. According to the NMR spectra, the active principles of the extracts seem to be water-soluble unsaturated compounds from the oils or their hydrolysis products. Natural substances provide an attractive alternative for preventive actions against schistosomiasis, as the perturbation of the ecological equilibrium of natural waters can be avoided in this manner.