## 3 Results and Discussion
### Docking-Based Interaction Simulations  
Before performing molecular docking on test compounds, it is essential to conduct a validation process to ensure the reliability and accuracy of the docking protocol. Validation involves redocking a known ligand into the active site of the target protein and comparing the predicted binding pose. The parameter used was the root mean square deviation (RMSD), where a method is considered valid if the RMSD value is less than 2 A [76]. The RMSD value measures the similarity of docking poses, with a higher RMSD value indicating less accurate pose predictions [77]. In this study, molecular docking was validated by redocking the native ligand (4-OHT) into the target protein 3 ERT (ER\(\alpha\)), to confirm and precisely determine the binding site on the protein. From this process, an RMSD value of 1.17 A was obtained, indicating that the molecular docking method met the qualifications and showed good quality of bond pose reproduction because the RMSD value was less \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Compound**} & \multicolumn{4}{c}{**Pharmacokinetic**} & \multicolumn{4}{c}{**Toxicity**} \\ \cline{2-10}  & \multirow{2}{*}{**HIA**} & \multirow{2}{*}{**Caco-2**} & \multirow{2}{*}{**PPB**} & \multicolumn{2}{c}{**Carcinogenicity**} & \multirow{2}{*}{**Impantotoxicity**} & \multirow{2}{*}{**Mutagenicity**} & \multirow{2}{*}{**Cytotoxicity**} & \multicolumn{2}{c}{**Toxicity**} \\ \cline{3-3} \cline{5-10}  & & & & **Mouse** & & & & & & & \\ \hline PBD-21 & 95.79 & 4.02 & 83.11 & No & No & No & No & No & No & 5 \\ \hline PBD-22 & 96.94 & 6.28 & 89.86 & No & No & No & No & No & No & 5 \\ \hline PBD-23 & 96.94 & 6.01 & 91.28 & No & No & No & No & No & No & 5 \\ \hline PBD-24 & 96.94 & 5.89 & 90.39 & No & No & No & No & No & No & 5 \\ \hline PBD-25 & 96.78 & 6.57 & 87.70 & No & No & No & No & No & No & 5 \\ \hline PBD-26 & 96.78 & 6.29 & 88.85 & No & No & No & No & No & No & 5 \\ \hline PBD-27 & 96.78 & 6.17 & 88.13 & No & No & No & No & No & No & 5 \\ \hline PBD-28 & 96.85 & 2.73 & 94.22 & No & No & No & No & No & No & 5 \\ \hline PBD-29 & 96.85 & 2.64 & 95.86 & No & No & No & No & No & No & 5 \\ \hline PBD-30 & 96.85 & 2.56 & 94.13 & No & No & No & No & No & No & 5 \\ \hline PBD-31 & 96.80 & 2.89 & 84.06 & No & No & No & No & No & No & 5 \\ \hline PBD-32 & 96.80 & 2.80 & 84.63 & No & No & No & No & No & No & 5 \\ \hline PBD-33 & 96.80 & 2.71 & 84.86 & No & No & No & No & No & No & 5 \\ \hline PBD-34 & 97.05 & 12.26 & 96.64 & No & No & No & No & No & No & 5 \\ \hline PBD-35 & 97.05 & 12.19 & 97.45 & No & No & No & No & No & No & 5 \\ \hline PBD-36 & 97.05 & 12.11 & 95.57 & No & No & No & No & No & No & 5 \\ \hline PBD-37 & 97.33 & 2.08 & 85.19 & No & No & No & No & No & No & 5 \\ \hline PBD-38 & 97.33 & 2.01 & 86.07 & No & No & No & No & No & No & 5 \\ \hline PBD-39 & 97.33 & 1.93 & 85.95 & No & No & No & No & No & No & 5 \\ \hline PBD-40 & 96.93 & 3.12 & 89.01 & No & No & No & No & No & No & 5 \\ \hline PBD-41 & 96.93 & 3.00 & 90.06 & No & No & No & No & No & No & 5 \\ \hline PBD-42 & 96.93 & 2.92 & 89.60 & No & No & No & No & No & No & 5 \\ \hline PBD-43 & 97.13 & 4.76 & 96.58 & No & No & No & No & No & No & 5 \\ \hline PBD-44 & 97.13 & 4.58 & 97.40 & No & No & No & No & No & 5 \\ \hline PBD-45 & 97.13 & 4.50 & 95.43 & No & No & No & No & No & 5 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: _Cont._than 2 A (Figure 3) with free energy of binding (\(\Delta\)G) value of \(-11.42\) kcal/mol with an inhibition constant (Ki) value of 4.26 uM. Further, re-docking 4-OHT produced hydrogen bond interactions with the residues amino acid ARG394, GLU353, and LEU387. Molecular docking was carried out to determine the possible interactions between the test compounds and important amino acid residues of the target protein (ER\(\alpha\)), compared to the native ligand and reference ligands. The molecular docking uses the grid box arrangement obtained in the validation process to center the test ligands with the active sites on the native ligands.