## 3 Results and Discussion
### Atomic Charge Calculation  
The results of the atomic charge calculation, which uses a simple calculation method and entails a relatively low calculation cost, are summarized in Table 4.  
The reaction between ACEL and ANT due to -OH radical oxidation starts as -OH, which has strong electrophilicity and attacks carbon because of the electron deficiency of the ring system. This indicates that examination of the electron density of carbon constituting ACEL and ANT is effective in analyzing the radical reaction. In other words, the electrical attraction with the electrophilic -OH radical increases with higher negative charge values of the carbon forming the ring of ACEL and ANT. Therefore, in this study, MK, CHelpG, and HLY charges were calculated with respect to the molecular structure obtained by optimization at the B3 LYP/6-31G(d,p) level. As shown in Table 4, the charge values were the same at the symmetrical positions of ACEL and ANT, which are symmetrical structures, as expected. Looking at the charge value of ACEL, the charge values at positions 5 and 6 were smaller (the largest negative charge value) than MK, CHelpG, and HLY charges at other positions. In addition, MK and HLY charge values were the second smallest at positions 1 and 2. Since the MK and HLY charge values at positions 1 and 2 did not differ significantly from those at positions 5 and 6, it is possible to predict the radical reaction position with the MK and HLY charge calculations. However, in the case of CHelpG charge, the charge of carbon at positions 3 and 8 was found to be the second smallest. In the existing literature, it is reported that the reaction occurs at positions 1 and 2, showing a difference from the calculation results. The MK and HLY charge values are in good agreement with those of the actual radical decomposition products. The charge values of ANT at positions 9 and 10 were found to be very small compared to those of MK, CHelpG, and HLY at other positions. Existing literature reports show that reactions occur at positions 9 and 10. Therefore, it can be confirmed that the contents of the literature are in exact agreement with the MK, HLY, and CHelpG charge values. In addition, oxygen OH radicals react with a specific carbon in ACEL and ANT, resulting in a quinone-type final product.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Position**} & \multicolumn{5}{c}{**Charge**} \\ \cline{2-7}  & **MK** & **CHelpG** & **HLY** & **MK** & **CHelpG** & **HLY** \\ \hline
1 & \(-\)0.295 & \(-\)0.215 & \(-\)0.259 & \(-\)0.254 & \(-\)0.223 & \(-\)0.247 \\ \hline
2 & \(-\)0.295 & \(-\)0.215 & \(-\)0.259 & \(-\)0.127 & \(-\)0.060 & \(-\)0.107 \\ \hline
3 & \(-\)0.256 & \(-\)0.249 & \(-\)0.251 & \(-\)0.127 & \(-\)0.060 & \(-\)0.107 \\ \hline
4 & \(-\)0.092 & 0.029 & \(-\)0.050 & \(-\)0.253 & \(-\)0.223 & \(-\)0.247 \\ \hline
5 & \(-\)0.305 & \(-\)0.317 & \(-\)0.315 & \(-\)0.253 & \(-\)0.223 & \(-\)0.247 \\ \hline
6 & \(-\)0.305 & \(-\)0.317 & \(-\)0.315 & \(-\)0.127 & \(-\)0.060 & \(-\)0.107 \\ \hline
7 & \(-\)0.092 & 0.029 & \(-\)0.050 & \(-\)0.127 & \(-\)0.060 & \(-\)0.107 \\ \hline
8 & \(-\)0.256 & \(-\)0.249 & \(-\)0.251 & \(-\)0.254 & \(-\)0.223 & \(-\)0.247 \\ \hline
9 & & & & \(-\)0.353 & \(-\)0.440 & \(-\)0.466 \\ \hline
10 & & & & \(-\)0.353 & \(-\)0.440 & \(-\)0.466 \\ \hline \hline \end{tabular}  
* Charges in electron.  
\end{table}
Table 4: Calculated atomic charge distributions of ACEL and ANT *.