This result indicates that their mitochondria are at least partially depolarized, which is consistent with the observed increase in intracellular Ca2+ concentration. Altogether, our results agree in part with the effects reported for benzothiazoles with antimicrobial activity in both Gram-positive and Gram-negative bacteria, although the effects are observed with 4-fold the MIC (between 3.91 and 15.6?g/ml) (29). and vertebrate hosts (5,C7). Replicative, noninfective epimastigotes present in the insect vector give rise to nonreplicative infective metacyclic trypomastigotes. These forms invade the host cell, establish the infection, and differentiate into replicative amastigotes. Amastigote forms give rise to a transient stage, named intracellular epimastigotes, which subsequently differentiate into trypomastigotes that can disseminate in the mammalian host through the bloodstream after causing lysis of host cells and are capable of infecting other cells. The insect vector can acquire these forms during its bloodmeal, becoming infected and able to infect a new mammalian host (8, 9). Human contamination is characterized by two sequential clinical phases: acute and chronic. The acute phase is usually often asymptomatic and usually remains undiagnosed. Most infected individuals proceed to the chronic phase, which continues for the rest of the patients life. The chronic phase presents several clinical forms: 70% of patients are asymptomatic, while the remaining 30% present clinical manifestations, with the most frequent being chagasic chronic cardiomyopathy and, more rarely, megavisceras (mainly megacolon and megaesophagus). Over years, the cardiac form of the infection can cause sudden death or heart failure due to the progressive destruction of the cardiac muscle Secalciferol (9). A century after the Secalciferol discovery of the disease by Carlos Chagas in 1909, only two nitroheterocyclic drugs, nifurtimox and benznidazole, are used to treat infection. These drugs are effective during acute contamination. However, their effectiveness during the chronic phase of CD is controversial due to their toxicity (10). Therefore, more secure, effective, and accessible alternatives are currently being sought to treat CD. (14); thus, it was proposed as a new nucleus for the development of trypanocidal agents. The aim of this contribution was to determine the trypanocidal activity of a collection of 14 benzothiazoles structurally related to Secalciferol BT3. We evaluated their anti-activity and analyze their physicochemical-structural characteristics responsible for its biological activity. BT10, the most promising molecule due to its higher Secalciferol selectivity index than the other derivatives, was selected for further analyzing its effects on different aspects of biology. We propose BT10 as a promising pharmacological hit compound for developing a treatment against CD. RESULTS BT10 affects the proliferation of epimastigotes. A collection of 14 structurally related molecules, named BT1 to BT14, was synthesized (Fig. 1A). The identification of the synthesized molecules and their chemical characterization were performed by melting point (mp), nuclear magnetic resonance (NMR), and electrospray ionization-mass spectrometry spectra determination (ESI-MS). These compounds were initially evaluated for their ability to inhibit epimastigote proliferation in the presence of 25?M BT1-14. We attributed a positive inhibition activity to those compounds that, at the concentration used, were able to diminish the cell density at the mid-exponential growth phase (which was measured around the 5th day from the beginning of incubation) by 50% or more. Epimastigotes cultured in the absence of drugs in the presence or absence of DMSO (which did not show significant differences) were used as negative controls for inhibition, and their cell density was considered 100% proliferation. For a positive control for the inhibition of cell proliferation, the parasites Rabbit polyclonal to ANKDD1A were incubated in the presence of a combination of 60?M rotenone plus 0.5?M antimycin (RA). The compound BT10 was identified as having trypanocidal or trypanostatic activity. BT10 produced a diminution of cell density of 50% compared to that of control (untreated) cultures. Despite not reaching the criterion for selecting them as trypanocidal/trypanostatic, it is worth mentioning that compounds BT3, BT9, and BT11 showed a modest but statistically significant decrease in cell density concentration compared to that of controls (Fig. 1B; see also Fig. S1 in the supplemental material). Because BT3 was used as the lead (14).