Leishmaniasis caused by protozoan Leishmania ssp., is an endemic parasitic disease in Central and South America. The Chemotherapic agents against Leishmania ssp. (pentavalent antimony compounds, pentamidine and amphothericine B) are toxic and expensive products. Basing on the Bolivian folk medicine, we tried to find new active principles. Fourteen isoquinoline alkaloids, especially bisbenzylisoquinoline alkaloids extracted from Annonaceae, Berberidaceae, Hernandiaceae and Menispermaceae, demonstrate highly effective activity against this protozoan. Among them gyrocarpine, daphnandrine and obaberine seem to be of particular interest. The therapeutic effect was studied by biological assays on culture forms in vitro three strains of Leishmania, L. donovani, L. braziliensis (cutaneous and mucocutaneous lieshmaniasis), L. mexicana amazonensis (cutaneous) and L. donovani (visceral leishmaniasis).