Evaluation of the anti-trypanosoma activity of alkaloids from Pilocarpus microphyllus by molecular docking: A search for new drugs for Chagas disease

Trypanosoma cruzi and Trypanosoma brucei, respectively, transmit the neglected tropical diseases (NTDs) Chagas disease and sleeping sickness. They cause symptoms that are harmful to public health. Treatment often has adverse effects, including high toxicity and neurosensory disorders. Studies aimed at developing pharmacological technologies are essential. In this study, we performed computational simulations based on in silico predictions. The amino acid sequence of the proteins for both parasites, T. cruzi and T. brucei, and their three-dimensional (3D) structures were obtained and drawn using the UniProt and Swiss model servers, respectively; later, they were used for in silico molecular docking studies. The GaussView software was used to get the two-dimensional (2D) and three-dimensional (3D) ligands of epiisopiloturine, epiisopilosine, pilosine, isopilosine, macaubine, and pilocarpine. To perform the optimization and frequency calculations of the alkaloids, the Gaussian 09w software and the Density Functional Theory (DFT) method were used with the hybrid functional B3LYP and the STO-3G support base. All the output files generated after the calculations were used to create the input files for the bond energy calculations. For the molecular docking studies, we have evaluated the side-ligands protein interactions and antiparasitic activity of the ligands. The anti-Trypanosomatidae potential of alkaloids extracted from Pilocarpus microphyllus “jaborandi” were evaluated by molecular docking. The results of the interactions of the 6 alkaloids: isopilosine, epiisopiloturine, epiisopilosine, pilocarpine, macubine and pilosine, with the proteins trypanothione reductase, sterol 14-alpha demethylase, phosphoinositide phospholipase c, farnesyl pyrophosphate synthase, nitroreductase, from the parasites T. cruzi and T. brucei, demonstrated that for 5 of them, the simulations showed minimums energy to be characterized as reactions that occur in biological systems spontaneously. For trypanothione reductase-epiisopilosine for both parasites, the alkaloid was observed to bind to the amino acid Glu467 through hydrogen bonds. For phosphoinositide phospholipase C-epiisopilosine, parameter values found were -8.2 Kcal.mol-1, only the amino acid Asn262 had interaction through hydrogen bonding. Other hydrophobic interactions were also observed between the proteins and epiisopilosine. Regarding the results of the alignment of amino acid sequences for both parasites, it was found a similarity of 83.30% and 52.38% between the nucleotide sequences of T. cruzi and T. brucei for trypanothione reductase and phosphoinositide phospholipase C, concluding that the best candidate for therapy against Chagas disease and sleeping sickness would be epiisopilosine alkaloid.