# COX2-Inhibitory and Cytotoxic Activities of Phytoconstituents of _Matricaria chamomilla_ L.
## 3 Results
### Molecular Docking In Silico  
To investigate the full potential of chamomile tea, a total of 212 chamomile compounds were docked against human COX2 (PDB: 5F1A) using the PyRx program. Thirty of these 212 compounds were selected as the most abundant for further analysis. Table 1 shows the low binding energies (LBE, kcal/mol) and the predicted inhibition constants (pKi, uM) of these 30 ligands. The LBE and pKi values of these phytochemicals correlated significantly with each other (Pearson correlation test, \(p\) = 7.53 \(\times\) 10 \(-\) 20; \(r\) = 0.574; Figure 1, 1 st line left panel). The LBE values of 27 out of 30 substances were smaller than \(-\)6 kcal/mol (cut-off) and ranged from \(-\)11.73 (\(\pm\)0.44) kcal/mol (\(\beta\)-sitosterol) to \(-\)6.01 (\(\pm\)<0.01) kcal/mol (P-cymene). The pKi values of these 27 compounds were in a range from 0.003 (\(\pm\)0.002) uM to 39.57 (\(\pm\)<0.01) uM. Seven of the 27 compounds were selected because these substances were found in the NCI database (dtp.cancer.gov, accessed on 1 July 2023), whose data are required for further investigations. Celecoxib was used as a positive control drug since it is a well-known COX2 inhibitor. As shown in Figure 3 (1 st line, middle, and right panel), the compounds were bound to three domains of COX2. Myricetin, daucosterol, and \(\beta\)-amyrin interacted with the first domain; \(\beta\)-sitosterol, apigenin, farnesol, and \(\beta\)-eudesmol with the second domain; and celecoxib with the third domain. Lines 2-5 of Figure 1 depict the three-dimensional binding poses of the compounds and the interacting amino acids. \begin{table}
\begin{tabular}{c l l l l} \hline
**No.** & **Compounds** & **LBE (kcal/mol)** & **pKi (uM)** & **Pharmacophore** \\ \hline
1. & \(\beta\)-Sitosterol & \(-\)11.73 \(\pm\) 0.33 & 0.003 \(\pm\) 0.002 &
\begin{tabular}{l} ALA199, ALA202, GLN203, THR206, HIS207, PHE210, THR212, HIS214, ASN382, TYR385, HIS386, TR387, \\ **HIS388**, LEU390, LEU391 \\ \end{tabular} \\ \hline
2 & \
\begin{tabular}{l} Celecoxib \\ \end{tabular} & \(-\)10.18 \(\pm\) 0.03 & 0.03 \(\pm\) \textless{}0.01 &
\begin{tabular}{l} **HIS90**, GLN192, LEU352, SER353, TYR355, LEU359, TR387, VAL523, ALA527 \\ \end{tabular} \\ \hline
3 & \(\beta\)-Amirin & \(-\)9.59 \(\pm\) 0.01 & 0.09 \(\pm\) \textless{}0.01 &
\begin{tabular}{l} LEU145, GLY225, HIS226, GLY227, **VAL228**, ASN375, ARG376, **GLY533**, **ASNS37**, VAL538 \\ \end{tabular} \\ \hline \end{tabular}
\end{table} 
Table 1: Molecular docking of 30 chamomile compounds binds to COX2 (PDB ID: 5F1A). Shown are the lowest binding energies (kcal/mol), predicted inhibition constants (uM), and the pharmacophores interacting between the ligands and COX2. Bold indicates hydrogen bonds. Figure 2: Dose–response curve of the extract of chamomile in hematopoietic and colon cancer cell lines determined by a resazurin assay. (**A**) Growth inhibition of CCRF-CEM leukemia cells and AMO-1 multiple myeloma cells. (**B**) Growth inhibition of HCT116 p53\({}^{+/+}\) wildtype and drug-resistant HCT116 p53\({}^{-/-}\) knockout cells. The IC\({}_{50}\) values were determined from the dose–response curve, and the degree of resistance was obtained by dividing the IC\({}_{50}\) value of HCT p53\({}^{-/-}\) by the IC\({}_{50}\) value of HCT p53\({}^{+/+}\). The mean values \(\pm\) standard deviation values are from three independent experiments.