Screening of medicinal plants against Leishmania amazonensis

Leishmaniasis is a widespread tropical infection caused by different species of Leishmania protozoa. There is no immunoprophylaxis (vaccination) available for Leishmania infections and conventional treatments are unsatisfactory; therefore antileishmanial drugs are urgently needed. Natural products are attractive due to their structural diversity.

The present work investigated the antileishmanial action of 21 species of plants.

Plants were collected and their hydroalcoholic extracts were screened against promastigotes and amastigotes of L. amazonensis. Their toxicity was also assayed against peritoneal macrophages from BALB/c mice.

Five extracts showed significant growth inhibitory activity against promastigote form. Only the extracts from Bidens pilosa L. (Asteraceae) and Punica granatum L. (Punicaceae) inhibited the growth of intracellular amastigotes, with IC(50) values of 42.6 and 69.6 microg/mL, respectively. In addition, a low toxicity on macrophage from BALB/c mice was observed.

The antiparasitic activities of B. pilosa and P. granatum have been reported against other parasitic agents and their actions can be the results of flavonoids present in the extracts.

This study supports the importance of natural products as potential sources in the search for new antileishmanial drugs.