Synthesis of thiosemicarbazone Schiff base derivatives as anti-leishmanial agents and molecular dynamics simulations insights

Abstract

Leishmaniasis is one of the infectious diseases caused by protozoa and is considered the second most significant parasitic disease after malaria. In this research, thiosemicarbazone Schiff base derivatives were synthesized via a one-pot, two-step, three-component reaction. Then, the effectiveness of the compounds against the two forms of Leishmania major and Leishmania tropica called amastigote and promastigote, was tested. All synthesized compounds displayed weak to good anti-amastigote and anti-promastigote activities. Notably, compounds 5g and 5p were the most potent compounds against amastigote and promastigote forms, respectively, of Leishmania major, with IC₅₀ = 26.7 µM and 12.77 µM. Analogues 5e and 5g were the most potent compounds against amastigote and promastigote forms of Leishmania tropica, with IC₅₀ = 92.3 µM and 12.77 µM, respectively. The cytotoxicity activity of the compounds was also evaluated using the J_774.A1 cell lines. Some of the screened derivatives displayed low cytotoxicity to macrophage infection. Among compounds, 5p and 5e showed the highest SI (95.4 and 34.6) against L. major and L. tropica, respectively. In the next phase, the most effective thiosemicarbazone derivatives were examined for their ability to induce apoptosis in promastigotes. According to the results, these compounds displayed different early and late apoptosis as well as necrotic effects on promastigotes of Leishmania major and Leishmania tropica. Furthermore, the compounds' drug-likeness and pharmacokinetic parameters were predicted in silico. All compounds showed acceptable drug-likeness and pharmacokinetic profiles. Furthermore, the most likely sites of the compounds metabolized by the major cytochromes were identified. Additionally, the in silico compounds' cardiotoxicity potential was assessed. This investigation showed compounds 5m-p were cardiotoxic. Lastly, molecular docking and molecular dynamics simulations were performed to explore the potential mechanisms of anti-leishmanial activity in the LmPRT1 active site.

Keywords: Amastigote; Apoptosis; Hydrazine-1-carbothioamide; Promastigote; Tropical disease.

Fig. 1

(A) FDA approved anti-leishmanial drugs (B) Compound drugs in clinical trials under diverse phases.

Fig. 2

Structure of some thiosemicarbazide shiff base-containing approved drugs.

Fig. 3

Design plan of thiosemicarbazone analogues as leishmanial agents.

Scheme 1

Synthesis of thiosemicarbazone analogues (5a-p).

Fig. 4

Structural synthesized thiosemicarbazone analogues (5a-p).

Scheme 2

Plausible mechanism for the formation of thiosemicarbazone Schiff base 5a-p.

Fig. 5

The necrotic and apoptotic profiles of the L. major and L. tropica promastigotes at IC₅₀ concentrations of various syntheses compared to Glucantime as a general drug in Leishmaniasis treatment.

Fig. 6

(A) 3D and (B) 2D interactions of compound 5g with LmPRT1 residues active site.

Fig. 7

(A) 3D and (B) 2D interactions of compound 5p with PRT1 residues active site.

Fig. 8

2D binding modes of compounds (A) 5a, (B) 5k, (C) 5o, and (D) 5b with LmPRT1 residues active site.

Fig. 9

2D binding modes of (A) compound 5d and (B) compound 5i with LmPRT1 residues active site.

Fig. 10

2D binding modes of (A) compound 5c and (B) compound 5l with PRT1 residues active site.

Fig. 11

Pharmacophore characteristics that have been recognized as essential factors in the complexes’ interaction in LmPRT1 active site.

Fig. 12

RMSD plot of LmPRT1 with molecules 5e (Green), 5g (Brown), 5p (Blue), and apo protein (Purple) throughout the simulation time.

Fig. 13

Superimposed RMSD of the ligands 5e (Green), 5g (Brown), and 5p (Blue) in complex with LmPRT1 enzyme.

Fig. 14

RMSF of the residues of apo LmPRT1 ((Purple) and LmPRT1 in complex with 5e (Green), 5g (Brown), and 5p (Blue), during overall 150 ns MD simulation.

Fig. 15

The protein backbone Rg during the MD, in the presence of 5e (Green), 5g (Brown), apo (Purple), and 5p (Blue).

Fig. 16

The protein backbone SASA during the MD, in the presence of 5e (Green), 5g (Brown), apo (Purple), and 5p (Blue).

Fig. 17

Number of hydrogen bonds made between compound and enzyme during simulation in the presence of 5e (Green), 5g (Brown), apo (Purple), and 5p (Blue).

Fig. 18

Principal component analysis (PCA). The eigenvector index of 5e, 5g, 5p, and apo protein during MD simulations.

Fig. 19

Principal component analysis (PCA). PC1 and PC2 of 5e (Blue), 5g (Purple), 5p (Green), and apo protein (Yellow) during MD simulations.

Fig. 20

Ramachandran plot of complexes and apo protein displaying > 90% of amino acids in the core region into active site of LmPRT1 enzyme.