Natural Products in Antileishmanial Drug Discovery: A Review

Leishmaniasis is a disease caused by the protozoan parasites, which belong to the genus Leishmania. Some known species of Leishmania include L. tropica, L. donovani, L. mexicana, L. aethiopica, L. Infantum, L. donovani, L. mexicana, L. braziliensis, L. chagasi and L. amazonensis. Leishmaniasis is transmitted through the bite of phlebotomine sandflies. The existence of Leishmaniasis has been recorded in several countries in the Mediterranean, Central and South America, Asia, Africa, the Middle East, China, India and the Caribbean. Chemotherapy and vector control are the known available means of combating the Leishmaniasis as the development of effective vaccines are still under way. Crude solvent extracts and isolated compounds from certain plants have however, shown significant activity against leishmanial parasite. Some of the plants reported to have antileishmanial activity include Tridax procumbens, Urechites andrieuxii Muell.-Arg. (Apocynaceae), Desmodiumgangeticum, Pseudelephantopusspicatus, Himatanthussucuuba,among others. Of the antileishmanial plants, the greatest number belonged to the Apocynaceae. Methanol extracts of the plants were mostly found to possess antileishmanial activity. The level of activity exhibited by the crude solvent extracts or the isolated constituent(s) depended largely on the type of solvent used for the extraction and also on the plant part used. The array of plants that have demonstrated antileishmanial activity suggests that the hope to discover novel antileishmanial drugs is high.