Synthesis and characterization of platinum-sterol hydrazone complexes with biological activity against Leishmania (L.) mexicana

Leishmaniasis is a parasitic zoonosis caused by protozoans of the genus Leishmania transmitted by insects known as phlebotomines, which are found in wild or urban environments. The disease occurs in tropical and sub-tropical areas, mainly in Asia, Europe, Africa and the Americas. At present, there is no effective treatment for this disease. In the search for new rational chemotherapeutic alternatives, two novel trans [Pt(Hpy1)(2)(Cl)(2)] (1) and trans [Pt(Hpy(2))(2) (Cl)(2)](2) complexes were synthesized by the reaction of K2PtCl4 with sterol hydrazone ligands 20-hydrazone-pyridin-2-yl-5 alpha-pregnan-3 beta-ol (Hpyl) and 22-hydrazone-pyridin-2-yl-chol-5-ene-3 beta-ol (Hpy2). These organic compounds are specific inhibitors of sterol methyl transferase (SMT). The new platinum complexes were characterized by a combination of ESI-MS (electrospray ionization-mass spectroscopy), UV-vis, infrared and NMR spectroscopies; elemental analysis and molar conductivity. Promastigotes of Leishmania (L.) mexicana were treated for 48 h with 10 mu M of the sterol hydrazones Hpy1 or Hpy2 alone or coordinated to Pt. Hpyl produced higher leishmanistatic activity than Hpy2 (39% growth inhibition vs. 16%), which significatively increased (71%, p < 0.001) when the complex trans-[Pt(Hpy1)(2)(Cl)(2)] was used. This complex represents a new chemotherapeutic alternative to be evaluated in depth in experimental models of leishmaniasis. (C) 2007 Elsevier Inc. All rights reserved.