Searching for new prospective antitrypanosomal agents, three novel Ru(II)-cyclopentadienyl compounds, [Ru(η(5)-C5H5)(PPh3)L], with HL=bioactive 5-nitrofuryl containing thiosemicarbazones were synthesized and characterized in the solid state and in solution. The compounds were evaluated in vitro on the blood circulating trypomastigote form of Trypanosoma cruzi (Dm28c strain), the infective form of Trypanosoma brucei brucei (strain 427) and on J774 murine macrophages and human-derived EA.hy926 endothelial cells. The compounds were active against both parasites with IC50 values in the micromolar or submicromolar range. Interestingly, they are much more active on T. cruzi than previously developed Ru(II) classical and organometallic compounds with the same bioactive ligands. The new compounds showed moderate to very good selectivity towards the parasites in respect to mammalian cells. The global results point at [RuCp(PPh3)L2] (L2=N-methyl derivative of 5-nitrofuryl containing thiosemicarbazone and Cp=cyclopentadienyl) as the most promising compound for further developments (IC50T. cruzi=0.41μM; IC50T. brucei brucei=3.5μM). Moreover, this compound shows excellent selectivity towards T. cruzi (SI>49) and good selectivity towards T. brucei brucei (SI>6). In order to get insight into the mechanism of antiparasitic action, the intracellular free radical production capacity of the new compounds was assessed by ESR. DMPO (5,5-dimethyl-1-pirroline-N-oxide) spin adducts related to the bioreduction of the complexes and to redox cycling processes were characterized. In addition, DNA competitive binding studies with ethidium bromide by fluorescence measurements showed that the compounds interact with this biomolecule.

In search of prospective agents against infectious diseases, 1,1'-bis(diphenylphosphino)ferrocene pyridine-2-thiolato-1-oxide M(ii) hexafluorophosphate compounds [M(mpo)(dppf)](PF6), where M = palladium or platinum, were synthesized and fully characterized in the solid state and in solution using experimental and DFT computational techniques. The compounds are isomorphous and the M(ii) transition metal ions are in a nearly planar trapezoidal cis-coordination bound to the pyridine-2-thiolato-1-oxide (mpo) and to the 1,1'-bis(diphenylphosphino)ferrocene molecules, both acting as bidentate ligands. Both compounds showed high cytotoxic activity on Trypanosoma cruzi and Mycobacterium tuberculosis (MTB) and acceptable selectivities towards MTB, but good to excellent selectivity index values as anti-T. cruzi compounds. The inclusion of the ferrocene moiety (dppf ligand) improved the selectivity towards the parasite when compared to the previously reported [M(mpo)2] complexes. Related to the probable mechanism of action of the complexes, molecular docking studies on modelled T. cruzi NADH-fumarate reductase (TcFR) predicted that both be very good inhibitors of the enzyme. The effect of the compounds on the enzyme activity was experimentally confirmed using T. cruzi protein extracts. According to all obtained results, both [M(mpo)(dppf)](PF6) compounds could be considered prospective anti-trypanosomal agents that deserve further research.

New Pd and Pt ferrocenyl derivatives showed submicromolar activities on T. cruzi and T. brucei and high selectivities.

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Searching for prospective agents against infectious diseases, four new ferrocenyl derivatives, [M(L)(dppf)4](PF), with M = Pd(II) or Pt(II), dppf = 1,1'-bis(dipheny1phosphino) ferrocene and HL = tropolone (HTrop) or hinokitiol (HHino), were synthesized and characterized. Complexes and ligands were evaluated against the bloodstream form of T. brucei, L. infantum amastigotes, M. tuberculosis (MTB) sensitive strain and MTB clinical isolates. Complexes showed a significant increase of the anti-T. brucei activity with respect to the free ligands (>28- and >46-fold for Trop and 6- and 22-fold for Hino coordinated to Pt-dppf and Pd-dppf, respectively), yielding IC values < 5 μM. The complexes proved to be more potent than the antitrypanosomal drug Nifurtimox. The new ferrocenyl derivatives were more selective towards the parasite than the free ligands. The Pt compounds were less toxic on J774 murine macrophages (mammalian cell model), than the Pd ones, showing selectivity index values (SI = IC murine macrophage/ICT. brucei) up to 23. Generation of the {M-dppf} compounds lead to a slightly positive impact on the anti-leishmanial potency. Although the ferrocenyl derivatives were more active on sensitive MTB than the free ligands (MIC = 9.88-14.73 μM), they showed low selectivity towards the pathogen. Related to the mechanism of action, the antiparasitic effect cannot be ascribed to an interference of the compounds with the thiol-redox homeostasis of the pathogen. Fluorescence measurements pointed at DNA as a probable target of the new compounds. [Pt(Trop)(dppf)](PF) and [Pt(Hino)(dppf)](PF) could be considered prospective anti-T. brucei agents that deserve further research.

2015): A new ruthenium cyclopentadienyl azole compound with activity on tumor cell lines and trypanosomatid parasites, Journal of Coordination Chemistry, As part of our efforts to develop organometallic ruthenium compounds bearing activity on both trypanosomatid parasites and tumor cells, a new Ru(II)-cyclopentadienyl clotrimazole complex, [RuCp(PPh 3 ) 2 (CTZ)](CF 3 SO 3 ) where Cp = cyclopentadienyl, CTZ = clotrimazole, was synthesized and characterized. The compound was evaluated in vitro on T. cruzi (Y strain), the infective form of T. brucei brucei strain 427 (cell line 449), on three human tumor cell lines with different sensitivity to cisplatin (A2780, ovary; MCF7, breast; HeLa, cervix) and on J774 murine macrophages as mammalian cell model. The new compound is more cytotoxic on T. cruzi and on the tumor cell lines than the reference drugs (Nifurtimox and cisplatin, respectively). In addition, complexation of the bioactive CTZ to the {RuCp(PPh 3 )} leads to significant increase of the antiparasitic and antitumoral activity. To get insight into the potential "dual" mechanism of antiparasitic action emerging from the presence of Ru(II) and CTZ in a single molecule, the inhibitory effect of this new complex on the biosynthesis of T. cruzi sterols of membrane and the interaction with DNA were studied. Although the tested complex does not affect DNA, it affects the T. cruzi biosynthetic pathway of conversion of squalene to squalene oxide. According to the results here reported, [RuCp(PPh 3 ) 2 (CTZ)][CF 3 SO 3 ] could be considered a prospective antiparasitic and/or antitumoral agent that deserves further evaluation.