Action of new organometallic complexes against Leishmania donovani.

The action of 16 newly synthesized metal complexes having the general structure cis-Pt-(II)-X n -L n have been tested in vitro against the promastigote forms of Leishmania donovani. The metal complexes at 24 h and maximum dosages inhibited growth from 0%, e.g. in cis-Pt-nifurtimox, to 100%, e.g. in cis-Pt-(2,3,4,5,6-pentafluoroaniline) 2 Br 2 or cis-Pt-pentamidine-I 2 . A study of the cytotoxicty of these latter complexes on the phagocytic cell line J-774 showed neither high cytotoxicity nor cytolysis. At the maximum dosage after 24 h of permanent contact with the cells (extreme, non-physiological conditions), cytolysis did not exceed 30%. For most of the compounds, cytolysis ranged from 0%, for cis-Pt-oxamniquine-Cl 2 to 27.7%, for cis-Pt-pentamidine-I 2 . The compound cis-Pt-(2,3,4,5,6-pentafluoroaniline) 2 -Br 2 caused up to 1.4% cytolysis under the above conditions. Parasites exposed to cis-Pt-pentamidine-I 2 showed notably reduced DNA, RNA and protein synthesis, unlike those exposed to other compounds. Parasites examined by electron microscopy showed effects mainly on the nucleus, though in some cases the mitochondria were affected, altering the internal membranes of the cytoplasmic organelles. The in-vivo activity of the complex cis-Pt-guanethidine-Cl 2 was evaluated in parasitized Wistar rats, in which the number of amastigotes per gram of spleen was reduced by 75% compared with controls.