Natural products and the development of selective antiprotozoal drugs

New drugs are urgently required for the treatment of amoebiasis, leishmaniasis, malaria and trypanosomiasis. In this review the potential of natural plant products as a source of antiprotozoal drugs is discussed with respect to biochemical differences between protozoa and hosts. Some of the ways in which pathogenic protozoa differ biochemically from their human hosts are described, and the modes of action of some antiprotozoal drugs which exploit these differences are mentioned. A selection of natural products of plant origin (alkaloids, terpenes, quinones and miscellaneous compounds) is illustrated with emphasis on their modes of action and potential for the development of selective antiprotozoal agents.