Optimization of 1,4-Naphthoquinone Hit Compound: A Computational, Phenotypic, and In Vivo Screening against Trypanosoma cruzi

Abstract

Chagas disease (CD) still represents a serious public health problem in Latin America, even after more than 100 years of its discovery. Clinical treatments (nifurtimox and benznidazole) are considered inadequate, especially because of undesirable side effects and low efficacy in the chronic stages of the disease, highlighting the urgency for discovering new effective and safe drugs. A small library of compounds (1a-i and 2a-j) was designed based on the structural optimization of a Hit compound derived from 1,4-naphthoquinones (C2) previously identified. The biological activity, structure-activity relationship (SAR), and the in silico physicochemical profiles of the naphthoquinone derivatives were analyzed. Most modifications resulted in increased trypanocidal activity but some substitutions also increased toxicity. The data reinforce the importance of the chlorine atom in the thiophenol benzene ring for trypanocidal activity, highlighting 1g, which exhibit a drug-likeness profile, as a promising compound against Trypanosoma cruzi. SAR analysis also revealed 1g as cliff generator in the structure-activity similarity map (SAS maps). However, compounds C2 and 1g were unable to reduce parasite load, and did not prevent mouse mortality in T. cruzi acute infection. Phenotypic screening and computational analysis have provided relevant information to advance the optimization and design of new 1,4-naphthoquinone derivatives with a better pharmacological profile.

Keywords: Trypanosoma cruzi; chemotherapy; compound optimization; naphthoquinones; trypanocidal activity.

Figure 1

Structure-activity similarity maps (SAS maps) for T. cruzi based on chemical structure and biological activity. SAS maps against trypomastigote (A) and intracellular amastigote (B) forms of T. cruzi. Each point represents a pairwise comparison of 1,4-naphthoquinones derivatives. The points are colored to pIC50 values using a continuous scale from low (blue) to high (red) power. R1 = not descriptive; R2 = similar structure and different activity (Cliff activity); R3 = Different structure and similar activity (Similarity cliff) and R4 = Similar structure and activity (Smooth SAR).

Figure 2

Physicochemical properties of 1,4-naphthoquinone series. Relationship of physicochemical properties between cLogP x Molecular Weight x Drug-likeness × number of aromatic rings (A); polar surface area x hydrogen bond acceptors x hydrogen bond donors x rotatable bonds (B,C) principal component analysis (PCA).

Figure 3

Effect of 1,4-naphthoquinone derivatives (C2 and 1g) in acute murine model of T. cruzi infection. Parasitemia levels (A) and survival rate (B) of mice intraperitoneally infected with T. cruzi trypomastigote forms (Y strain) and submitted to different treatment regimens (n = 5 animals/group).

Figure 4

Structure and yields of 2-hydroxy-3-phenylsulfanylmethyl-[1-4]-naphthoquinone derivates.