The antitumoral depsipeptide IB-01212 kills Leishmania through an apoptosis-like process involving intracellular targets.

IB-01212, an antitumoral cyclodepsipeptide isolated from the mycelium of the marine fungus Clonostachys sp., showed leishmanicidal activity at a low micromolar range of concentrations on promastigote and amastigote forms of the parasite. Despite its cationic and amphipathic character, shared with other membrane active antibiotic peptides, IB-01212 did not cause plasma membrane lesions large enough to allow the entrance of the vital dye SYTOX green (MW = 600), even at concentrations causing full lethality of the parasite. Having ruled out massive disruption of the plasma membrane, we surmised the involvement of intracellular targets. Proof of concept for this assumption was provided by the mitochondrial dysfunction caused by IB-01212, which finally caused the death of the parasite through an apoptotic-like process. The size of the cycle, the preservation of the C2 symmetry, and the nature of the bonds linking the two tetrapeptide halves participate in the modulation of the leishmanicidal activity exerted by this compound. Here we discuss the potential of IB-01212 as a lead for new generations of surrogates to be used in chemotherapy treatments against Leishmania .