3.4 Binding Interaction of Active Compound Fraction 49 to Protein Targets
The analysis of the binding interactions between the active compounds with the target protein was performed using the LigPlot software. The interactions obtained involve hydrophobic binding interactions (Fig. 1). Dibutyl phthalate has 1 hydrogen bond with Phe483(A), similar to the hydrophobic bond in the control ligand with PfK13. It forms 11 hydrophobic bonds, with 6 of them (His719(A), Tyr482(A), Ser720(A), Gly718(A), Ser624(A), Gly625(A)) being identical to both hydrogen and hydrophobic bonds in the control ligand with PfK13. For PfPM2, Dibutyl phthalate has 2 interacting hydrogen bonds (Arg307(A), similar to the hydrophobic bond in the control ligand) and forms 8 hydrophobic bonds, with 5 of them (Tyr272(A), Val160(A), Gln275(A), Glu271(A), His276(A)) being similar to the hydrophobic bonds in the control ligand with PfPM2. For PfAMA-1, Dibutyl phthalate has no hydrogen bonds, matching the control ligand, but has 9 hydrophobic bonds, with 7 of them (Lys364(A), Tyr390(A), Arg143(A), Pro350(A), Gln349(A), Glu365(A), Glu361(A)) being similar to the hydrophobic bonds in the control ligand with PfAMA-1. These interactions suggest the potential of Dibutyl phthalate as an antimalarial drug, especially against PfK13 and PfPM2.
Dihydroyashabushiketol has 2 hydrogen bonds (Gly533(A), Ser485(A)) identical to the hydrophobic bond of the control ligand on PfK13. It forms 12 hydrophobic bonds, with 7 of them (Ala578(A), Gly625(A), Tyr482(A), His719(A), Gly718(A), Phe483(A), Ser720(A)) being similar to the control ligand on PfK13. For PfPM2, Dihydroyashabushiketol has 3 hydrogen bonds (Arg307(A), Tyr272(A), Gln275(A)) similar to the hydrophobic bonds in the control ligand, and has 7 hydrophobic bonds, with 3 of them (His276(A), Val160(A), Glu271(A)) being similar to the hydrophobic bonds in the control ligand with PfPM2. For PfAMA-1, Dihydroyashabushiketol has 2 hydrogen bonds (Arg143(A), Lys364(A)) similar to the hydrophobic bonds in the control ligand, and has 6 hydrophobic bonds, with 5 of them (Tyr390(A), Pro350(A), Lys351(A), Glu361(A), Glu365(A), Gln349(A)) being similar to the hydrophobic bonds in the control ligand with PfAMA-1. These interactions indicate the potential of Dihydroyashabushiketol as an antimalarial drug, especially against PfK13, PfPM2, and PfAMA-1.
Dibenzylamine has 2 hydrogen bonds (Ser720(A), Phe483(A)) identical to the hydrophobic bond of the control ligand with PfK13. It has 9 hydrophobic bonds, with 5 of them (His719(A), Ala578(A), Gly625(A), Gly718(A), Tyr482(A)) being similar to both hydrogen and hydrophobic bonds in the control ligand with PfK13. For PfPM2, Dibenzylamine has 1 hydrogen bond (Glu271(A)) similar to the hydrophobic bond in the control ligand and forms 7 hydrophobic bonds, with 4 of them (Gln275(A), Val160(A), Arg307(A), Tyr272(A)) being similar to the hydrophobic bonds in the control ligand with PfPM2. For PfAMA-1, Dibenzylamine has no hydrogen bonds, similar to its control ligand, but has 7 hydrophobic bonds (Glu365(A), Tyr390(A), Gln349(A), Lys364(A), Arg143(A), Pro350(A), Glu361(A)) similar to the hydrophobic bonds in the control ligand with PfAMA-1. These interactions suggest that Dibenzylamine has the potential to bind with PfK13, PfPM2, and PfAMA-1 as an antimalarial drug.
Sedanolide has 1 hydrogen bond that does not share similarity with the control ligand with PfK13. It has 11 hydrophobic bonds, with 7 of them (Gly625(A), Ala578(A), His719(A), Phe483(A), Gly718(A), Tyr482(A), Ser720(A)) being similar to both hydrogen and hydrophobic bonds in the control ligand with PfK13. For PfPM2, Sedanolide has 1 hydrogen bond (Arg307(A)) similar to the hydrophobic bond in the control ligand and forms 4 hydrophobic bonds, with 3 of them (Tyr272(A), Val160(A), Glu271(A)) being similar to the hydrophobic bonds in the control ligand with PfPM2. For PfAMA-1, Sedanolide has no hydrogen bonds, similar to its control ligand, but has eight hydrophobic bonds, with 7 of them (Tyr390(A), Lys364(A), Arg143(A), Pro350(A), Glu365(A), Gln349(A), Glu361(A)) similar to the hydrophobic bonds in the control ligand with PfAMA-1.
3.5 Molecular Dynamic Analysis
The results of molecular dynamics simulations require analysis, such as RMSD and RMSF analysis. The RMSD values for Dihydroyashabushiketol-PfK13 were lower (mean 2.49 Å) compared to the control ligand (mean 4.51 Å). Dihydroyashabushiketol-PfK13 exhibited a stable graph during the simulation, indicating that the protein could maintain its position well over 100 ns. The RMSD simulation for Dihydroyashabushiketol-PfPM2 showed an unstable graph with higher values (mean 3.07 Å) compared to its control (mean 2.22 Å). Meanwhile, the RMSD simulation for Dihydroyashabushiketol-PfAMA-1 (mean 2.18 Å) was similar to its control ligand (mean 2.06 Å), refer to Fig. 2. Therefore, Dihydroyashabushiketol has the potential for better binding stability with the PfK13 target protein and the same binding stability as its control with the PfAMA-1 target protein. However, the RMSD for Dihydroyashabushiketol-PfPM2 indicates an unstable binding.
The binding of the compound Dihydroyashabushiketol with PfK13, PfPM2, and PfAMA-1, it was found that there were low fluctuations in the same amino acids as the control, indicating that this ligand has the potential to act as an antagonist against each target protein (Fig. 3).
The average binding energy value of Dihydroyashabushiketol-PfK13 (6,115 Kcal/mol) is higher than PfK13-Artemisinin (1,968 Kcal/mol). The average binding energy value of Dihydroyashabushiketol-PfPM2 (-8,301 Kcal/mol) is higher than PfPM2-Piperaquine (-131,021 Kcal/mol). Meanwhile, the average binding energy value of Dihydroyashabushiketol-PfAMA-1 (-102,734 Kcal/mol) is lower than PfAMA-1-Artemisinin (-87,622 Kcal/mol) (Fig. 4). This shows that the affinity and stability of the Dihydroyashabushiketol ligand towards PfAMA-1 is better than the Artemisinin ligand (control).