## 3 Results and Discussion
### Docking-Based Interaction Simulations
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Legend**} & \multicolumn{2}{c}{**Inhibition Constant (nM)**} & \multicolumn{2}{c}{**Binding Energy (kcal/mol)**} & \multicolumn{2}{c}{**Intermolecular Energy (kcal/mol)**} & \multicolumn{2}{c}{**Torsional Energy (kcal/mol)**} & \multicolumn{2}{c}{**Ligand**} & \multicolumn{2}{c}{**Inhibition Constant (nM)**} & \multicolumn{2}{c}{**Binding Energy (kcal/mol)**} & \multicolumn{2}{c}{**Intermolecular Energy (kcal/mol)**} & \multicolumn{2}{c}{**Torsional Energy (kcal/mol)**} \\ \hline
12 & 152.58 & \(-9.30\) & \(-11.39\) & 2.09 & 36 & 120.10 & \(-9.44\) & \(-11.53\) & 2.09 \\ \hline
13 & 15.08 & \(-10.67\) & \(-12.46\) & 1.79 & 37 & 31.20 & \(-10.24\) & \(-12.33\) & 2.09 \\ \hline
14 & 39.26 & \(-10.10\) & \(-11.89\) & 1.79 & 38 & 58.24 & \(-9.87\) & \(-11.96\) & 2.09 \\ \hline
15 & 260.53 & \(-8.98\) & \(-10.77\) & 1.79 & 39 & 254.64 & \(-9.00\) & \(-11.08\) & 2.09 \\ \hline
16 & 8.26 & \(-11.03\) & \(-13.41\) & 2.39 & 40 & 29.89 & \(-10.27\) & \(-12.65\) & 2.39 \\ \hline
**17** & **6.08** & \(-11.21\) & \(-13.60\) & **2.39** & 41 & 88.58 & \(-9.62\) & \(-12.01\) & 2.39 \\ \hline
18 & 20.01 & \(-10.50\) & \(-12.89\) & 2.39 & 42 & 440.16 & \(-8.67\) & \(-11.06\) & 2.39 \\ \hline
19 & 14.19 & \(-10.71\) & \(-13.09\) & 2.39 & 43 & 8.12 & \(-11.04\) & \(-13.13\) & 2.09 \\ \hline
**20** & **6.71** & \(-11.15\) & \(-13.54\) & **2.39** & 44 & 9.52 & \(-10.94\) & \(-13.03\) & 2.09 \\ \hline
21 & 14.44 & \(-10.70\) & \(-13.08\) & 2.39 & 45 & 90.96 & \(-9.61\) & \(-11.69\) & 2.09 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: \(Cont.\)  
All PBD compounds have higher \(\Delta\)G and Ki values compared to the comparative compounds available on the market, namely 4-OHT, raoloxifene, and lasofoxifene. The PBD compounds with the smallest \(\Delta\)G values are PBD-17 (\(-\)11.21 kcal/mol) and PBD-20 (\(-\)11.15 kcal/mol). These \(\Delta\)G values are nearly identical to those of 4-OHT, suggesting that PBD-17 and PBD-20 may exhibit similar interactions to 4-OHT and have potential as  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Compound**} & \multicolumn{2}{c}{**Hydroogen Bond**} & \multicolumn{4}{c}{**Hydrophobic**} \\ \cline{2-10}  & **Conventional** & **Carbon** & **H-Bond** & **Alkyl and Pi-Alkyl** & **Pi-Sigma** & **Pi-Pi** & **Si-Pi** & **Si-Pi** & **Amide-Pi** & **Pi-Anion** & **Pi-Sulfur** \\ \hline \multirow{3}{*}{PBD-28} & & & **AA350, LEU346**, & & & & & & \\  & & & LEU349, LEU387, & & & & & & & \\  & & & LEU349, LEU387, & & & & & & & \\  & & & LEU391, LEU387, & & & & & & & \\  & & & LEU387, LEU388, & & & & & & \\ \hline \multirow{3}{*}{PBD-29} & **ARG394** & & **AA330, LEU346**, & & & & & & & \\  & & & LEU354, LEU384, & & & & & & \\  & & & LEU387, LEU382, & & & & & & \\  & & & LEU387, LEU382, & & & & & & \\  & & & & LEU387, LEU382, & & & & & \\  & & & & LEU387, LEU384, & & & & & \\  & & & & LEU388, LEU386, & & & & & \\  & & & & LEU389, LEU387, & & & & & & \\  & & & & LEU389, LEU384, & & & & & & \\  & & & & LEU389, LEU386, & & & & &anti-breast cancer agents. The PBD-17 and PBD-20 compounds formed hydrogen bonds with the same amino acids as the native ligand (4-OHT), namely ARG-394, GLU-353, and LEU-387. Additionally, both also interacted with GLU-353, a residue commonly involved in binding with the comparator ligands raloxifene and lasofoxifene, (Figure 4). Hydrogen bonding between the test ligand and the same amino acid residue on the natural ligand or the comparator ligand suggests similarity in interaction type, illustrating the similarity of activity [79]. These data demonstrated that PBD-17 and PBD-20 have the potential for stability and favorable binding affinity within the target receptor active region. On the other hand, a compound is deemed antagonistic to the ER\(\alpha\) receptor when it does not interact with certain amino acid residues, especially His524 [80].