Infections with protozoan parasites are a major cause of disease and mortality in many tropical countries of the world.
Diseases caused by species of the genera Trypanosoma (Human African Trypanosomiasis and Chagas Disease) and Leishmania (various
forms of Leishmaniasis) are among the seventeen “Neglected Tropical Diseases” (NTDs) defined as such by WHO due to the neglect of
financial investment into research and development of new drugs by a large part of pharmaceutical industry and neglect of public
awareness in high income countries. Another major tropical protozoan disease is malaria (caused by various Plasmodium species), which
-although not mentioned currently by the WHO as a neglected disease- still represents a major problem, especially to people living under
poor circumstances in tropical countries. Malaria causes by far the highest number of deaths of all protozoan infections and is often (as in
this review) included in the NTDs.
The mentioned diseases threaten many millions of lives world-wide and they are mostly associated with poor socioeconomic and
hygienic environment. Existing therapies suffer from various shortcomings, namely, a high degree of toxicity and unwanted effects, lack
of availability and/or problematic application under the life conditions of affected populations. Development of new, safe and affordable
drugs is therefore an urgent need.
Nature has provided an innumerable number of drugs for the treatment of many serious diseases. Among the natural sources for new
bioactive chemicals, plants are still predominant. Their secondary metabolism yields an immeasurable wealth of chemical structures
which has been and will continue to be a source of new drugs, directly in their native form and after optimization by synthetic medicinal
chemistry. The current review, published in two parts, attempts to give an overview on the potential of such plant-derived natural
products as antiprotozoal leads and/or drugs in the fight against NTDs.