Plant Terpenoids as Lead Compounds Against Malaria and Leishmaniasis

Abstract Diseases caused by protozoan parasites such as Trypanosoma sp., Leishmania sp., and Plasmodium sp. are a major cause of morbidity, disability, and mortality in several tropical countries. Leishmaniasis and trypanosomiasis affect millions of people and are included in the list of “Neglected Tropical Diseases,” defined by World Health Organization (WHO) as a diverse group of diseases that mainly affect populations living in poverty, without adequate sanitation and in close contact with infectious vectors and domestic animals and livestock. They are also considered as neglected due to general lack of attention in developed countries, as well as almost nonexistent financial investment on research and development of new drugs and vaccines. Although not considered a neglected disease, malaria, which is caused by several species of the Plasmodium genus, is one of the most widespread protozoan diseases, with 212 million cases worldwide in 2015. Currently, the treatment of these protozoan diseases is not ideal, being based on extremely toxic drugs with several side effects, limited efficacy, and high cost. Moreover, the increasing resistance of parasites to the available drugs, mostly with malaria, is another extremely serious problem to overcome. For these reasons, there is an urgent need for new, safe, and affordable therapeutics. A promising approach to achieve this goal is the study of natural products derived from plants. Particularly in the last several decades, traditionally medicinal plants have received the attention of the scientific community due to the increasingly urgent need not only to develop new and effective drugs, but also to provide scientific evidence for the use of these medicines. This chapter will cover the latest results on terpenes isolated from plants and their semisynthetic derivatives, with antiprotozoal activity, from 2010 to 2017. Some aspects concerning the relationship between structure and activity will be explored, as well as an updated review of new drugs introduced in clinical trials.