In addition, Selleckchem CHIR98014 juglone (NQ7) and its derivatives, including those brominated at C-2 (NQ10 to NQ12) or C-3 (NQ13 to NQ15) and 2-methyl-5-hydroxy-1,4-naphthoquinone (NQ16), were also

examined. Fourteen compounds displayed an IC50 in the range of 0.16 to 6.51 μM, demonstrating higher activity than Bz (26.0 μM), and the other two tested compounds were less active: NQ3 (563.18 μM) and NQ4 (63.02 μM) (Table 1). Table 1 Activity of the naphthoquinones on bloodstream trypomastigotes of T. cruzi at 37°C Cpd Nomenclaturea IC50/24 h (μM) NQ1 1,4-Naphthoquinone 0.79 ± 0.02 NQ2 2-Methyl-1,4-naphthoquinone Selleck Adriamycin (menadione) 6.04 ± 0.35 NQ3 2-Hydroxy-1,4-naphthoquinone (lawsone) 563.18 ± 83.28 NQ4 2-Acetoxy-1,4-naphthoquinone 63.02 ± 5.8 NQ5 2-Bromo-1,4- naphthoquinone 1.37 ± 0.03 NQ6 2,3-Dichloro-1,4- naphthoquinone Trichostatin A supplier (dichlone) 2.17 ± 0.29 NQ7 5-Hydroxy-1,4-naphthoquinone (juglone) 6.51 ± 0.48 NQ8 5-Acetoxy-1,4- naphthoquinone 0.16 ± 0.01 NQ9 5-Methoxy-1,4-naphthoquinone 1.02 ± 0.29 NQ10 2-Bromo-5-hydroxy-1,4-naphthoquinone 2.15 ± 0.22 NQ11 2-Bromo-5-acetoxy-1,4-naphthoquinone 2.43 ± 0.50

NQ12 2-Bromo-5-methoxy-1,4-naphthoquinone 1.25 ± 0.26 NQ13 3-Bromo-5-hydroxy-1,4-naphthoquinone 2.52 ± 0.37 NQ14 3-Bromo-5-acetoxy-1,4-naphthoquinone 0.85 ± 0.08 NQ15 3-Bromo-5-methoxy-1,4-naphthoquinone 1.41 ± 0.15 NQ16 2-Methyl-5-hydroxy-1,4-naphthoquinone (plumbagin) 1.38 ± 0.26 Bz Benznidazole 26.0 ± 4.0 aThe bromo derivatives (NQ10-NQ15) are named based on the core juglone (NQ7) system. Among the most active compounds on trypomastigotes at 37°C, four were selected for further

studies: the prototype naphthoquinone (NQ1) and three juglone derivatives (NQ8, NQ9 and NQ12) (Figure 1). Interestingly, their activity against trypomastigotes was not decreased when the experiments were performed at 4°C in culture medium, but at this lower temperature in the presence of whole blood, IC50 values higher than 500 μM were obtained (data not shown). Figure 1 Chemical structures of the studied naphthoquinones. Activity on the proliferative forms of T. cruzi and toxicity to mammalian cells The selected compounds (NQ1, NQ8, NQ9 and NQ12) were also assayed using the anti-PD-1 monoclonal antibody proliferative forms of T. cruzi: axenic epimastigotes and intracellular amastigotes. A dose-dependent effect on epimastigotes was observed, leading to the IC50 values for proliferation inhibition for 1 to 4 days of treatment displayed in Table 2. Comparing the four NQs, the prototype unsubstituted quinone NQ1 was the most active against epimastigotes. Table 2 IC 50 values (μM) of the naphthoquinones on the proliferation of T. cruzi epimastigotes Cpd 1 day 2 days 3 days 4 days NQ1 0.30 ± 0.08a 0.24 ± 0.03 0.26 ± 0.04 0.26 ± 0.05 NQ8 0.76 ± 0.12 0.35 ± 0.09 0.24 ± 0.10 0.36 ± 0.07 NQ9 2.62 ± 0.38 1.05 ± 0.19 1.08 ± 0.17 1.27 ± 0.21 NQ12 0.55 ± 0.01 0.48 ± 0.06 0.45 ± 0.05 0.44 ± 0.11 aMean ± standard deviation of at least three independent experiments. The NQs were added to T.