Computational modeling-assisted discovery of the structural effects of phenylpropanoid derivatives on intracellular anti-Trypanosoma cruzi activity.

Previous investigations have demonstrated that n-hexacosyl p-coumarate, a natural product isolated from the Brazilian plant Baccharis sphenophylla, exhibits activity against the extracellular (trypomastigote) forms of Trypanosoma cruzi. Structural modification of this compound led to the synthesis of the n-hexyl p-coumarate derivative, which showed significantly improved bioactivity, achieving an EC₅₀ value of 1.7 μM and a selectivity index of 71 against trypomastigote forms. However, when tested against intracellular amastigote forms, the compound displayed only moderate activity (EC₅₀ = 13 μM) and some cytotoxicity (CC₅₀ = 120 μM). To enhance efficacy and minimize toxicity, the double bond between C-7 and C-8 was reduced to a single bond, affording a series of phloretic acid derivatives (3a-3f). These derivatives were synthesized via Fischer esterification and evaluated for their in silico ADMET properties, which indicated improved drug-likeness profiles. Notably, phloretic acid derivatives exhibited substantially lower cytotoxicity (CC₅₀ > 200 μM) compared with the p-coumaric acid analogues, while maintaining potent activity against amastigote forms (EC₅₀ ≈ 10 μM), comparable to the reference drug benznidazole. A structure-activity relationship (SAR) analysis based on machine learning was performed using a deep neural network (DNN) model combined with SHAP interpretation, allowing identification of key molecular fragments influencing predicted EC₅₀ values, as well as their correlation with molecular flexibility and lipophilicity. Collectively, these results underscore the potential of phloretic acid derivatives as lead candidates for the development of new anti-T. cruzi agents.