ER-α (protein data bank ID: 3ERT) was used in this research for screening compound mechanism against breast cancer cells activity. The 3-dimensional structures were retrieved from RSCB Protein Data Bank (https://www.rcsb.org/) obtained in PDB format. Afimoxifene (4-OHT) was used as a positive control ligand and estradiol ligand for comparison. The 3D structures of the compounds were modeled by using Biovia Discovery Studio program (Mukund et al., 2019) .
Autodock Vina (open-source software PyRx 0.8) was used for the ligand-protein docking and virtual screening for anticancer activity of the compounds. Compound 1, compound 2, 4-OHT, and estradiol were subjects for binding to ER-α as protein target, the ligand was free for blind docking. Before the ligand is thetered to the receptor, it is necessary to identify the active pocked that binds to the receptor through grid parameters. The grid box was produced by redocking tamoxifen against ERα is x=30.282; y=1.1913; z=24.207 with a space volume of 40x40x40 points. The conformation was selected based on binding energy, the one with the lowest binding affinity score. The docking simulation was performed at the center of the active side of the receptor with coordinates (x = 30.010, y = -1.913, and z = 24.207) selected.
The docking results were visualized by using Biovia Discovery Studio program. Ligand-residue interaction and docking poses in the 3-dimension molecular picture were showed by the program. The docking pose of each protein-ligand complex was compared by looking at the side of the amino acid residue that binds the ligand. The similarity from ligation poses of compound 1 and 2, 4-OHT, and estradiol that bound on amino acid residues was determined and the relation of the docking pose of the ligands and protein targets being studied was selected. Prediction of pharmacokinetics was carried out with a SMILE structure analyzed using swiss ADME http://www.swissadme.ch/index.php) (Daina et al., 2017) .
Autodock Vina (open-source software PyRx 0.8) was used for the ligand-protein docking and virtual screening for anticancer activity of the compounds. Compound 1, compound 2, 4-OHT, and estradiol were subjects for binding to ER-α as protein target, the ligand was free for blind docking. Before the ligand is thetered to the receptor, it is necessary to identify the active pocked that binds to the receptor through grid parameters. The grid box was produced by redocking tamoxifen against ERα is x=30.282; y=1.1913; z=24.207 with a space volume of 40x40x40 points. The conformation was selected based on binding energy, the one with the lowest binding affinity score. The docking simulation was performed at the center of the active side of the receptor with coordinates (x = 30.010, y = -1.913, and z = 24.207) selected.
The docking results were visualized by using Biovia Discovery Studio program. Ligand-residue interaction and docking poses in the 3-dimension molecular picture were showed by the program. The docking pose of each protein-ligand complex was compared by looking at the side of the amino acid residue that binds the ligand. The similarity from ligation poses of compound 1 and 2, 4-OHT, and estradiol that bound on amino acid residues was determined and the relation of the docking pose of the ligands and protein targets being studied was selected. Prediction of pharmacokinetics was carried out with a SMILE structure analyzed using swiss ADME http://www.swissadme.ch/index.php) (Daina et al., 2017) .
