RESUMEN
The present study is focused on the isolation and identification of new therapeutic candidates from Chrysanthellum americanum Vatke., and their efficacy against pteridine reductase-1 (PTR1), a valid chemotherapeutic target in the Leishmania parasite. Henceforth, a new compound, chrysanamerine (1), along with 7 known compounds, polyacetylene 2, and flavonoids 3-8, were isolated from C. americanum. Their structures were determined by chemical and spectroscopic analyses and compared with the reported spectroscopic data. All compounds were evaluated for their anti-leishmanial activity against PTR1 via biochemical mechanism-based assay. The in vitro results showed five potential hits including a new compound, chrysanamerine (1), and four known compounds against the PTR1 enzyme. Among them, compound 1 showed a potent enzyme inhibition with an IC50 of 31.02 ± 2.36 µM, whereas a moderate inhibition was observed in cases of compounds 5 and 6 (IC50 = 59.86 ± 3.32, and 45.32 ± 3.5 µM, respectively). Whereas, compounds 3 and 8 showed mild inhibition (IC50 = 72.12 ± 1.12, and 97.18 ± 1.23 µM, respectively) against PTR1, compared with trimethoprim (positive control) (IC50 = 21.07 ± 1.6 µM). Moreover, the results were further validated via molecular docking and molecular dynamics (MD) simulations. Compound 1 showed a strong affinity to the binding site with a docking score of -11.83, along with the formation of a stable protein-ligand complex over the trajectory of 100 ns. Besides, compounds 1-8 were found to be non-cytotoxic on BJ (human fibroblast) cells.