**Author details**

the presence of a great quantity of cell remains in supernatant. Likewise parasites had strongly electrodense cytoplasm with intense vacuolization, with both empty vacuoles and membranes, and reservosomes, which appeared in greater numbers than in non-treated promastigotes

On the other hand, compound 1 was again very effective against *L. braziliensis* as some parasites appeared dead and others completely altered (Figure 11e), replete with reservosomes and enormous vacuoles. Some promastigotes appeared to be distorted and strongly electrodense, and showed condensed kinetoplast and very swollen mitochondria. In contrast, compound 3 was effective against *L. infantum* (Figure 11d), whose alterations were similar to those already described, with unrecognizable parasites, filled with vacuoles, which distorted their morphol‐ ogy, as well as a great quantity of reservosomes that occupied practically the entire cytoplasm. In these parasites kinetoplast and mitochondria also appeared swollen, resulting in a strongly

In addition to these studies, it should be noted that compounds 1-3 have displayed a high *in vitro* activity against both extra and intracellular forms of *T. cruzi* and are effective at concen‐ trations similar to those of benznidazole. At the same time, they are much less toxic for host cells than the latter. Moreover antileishmanial activity of metal compounds is much higher than that of isolated HmtpO ligand, which is an evidence of the critical role of metal ions in antiparasitic activity. Furthermore, promising *in vivo* activity was observed for all of them,

In comparison with economically more attractive diseases like cancer, cardio-vascular problems and allergies, commercial interest in developing new antiparasitics is still rather low. Low income of most of the people affected by leishmaniasis, as it is the case for other tropical diseases, discourages big pharmaceutical companies from investing in developing new therapies. Therefore there is an urgent need to investigate into new drugs with low cost of

Research on metal-based compounds to treat leishmaniasis has resurged in the last years and significant progress has been made. The possibility to finely tune their reactivity through a change of the metal ion and appropiate choice of the ligand/s makes of metal compounds

Optimization of currently available metal-based drugs such as antimonials through use of nanovehicles and attachment of targeting moieties may be an interesting option to overcome antimonials resistance problems and maybe the quickest way to produce effective results. Therapeutic effects might be enhanced by using e.g. metal nanoparticles as delivery carriers, which depending on the metal, might be able to produce high amounts of reactive oxygen

electrodense cytoplasm. Dead parasites were also visible.

488 Leishmaniasis - Trends in Epidemiology, Diagnosis and Treatment

with results consistent with those observed *in vitro*.

production but also with high efficacy and selectivity.

species and induce oxidative stress to the parasites.

promising alternatives to fight this disease in a cost-effective way.

**4. Conclusion and future trends**

(Figure 11a).

**3.5. Final remarks**

Ana B. Caballero1 , Juan M. Salas2 and Manuel Sánchez-Moreno3

1 School of Chemistry, University of Birmingham, Birmingham, United Kingdom

2 Department of Inorganic Chemistry, School of Sciences, University of Granada, Granada, Spain

3 Department of Parasitology, School of Sciences, University of Granada, Granada, Spain
