## 3 Results and Discussions
### MTT Assay  
The effects of total triterpenoids and isolated pure compounds on the proliferative response of the SK-Br-3, MCF-7, and T47D cell lines have been determined by treatment with different concentrations of the extracts. Significant reductions in cell proliferation were observed, and median inhibitory concentration values indicated that proliferation and growth of T47D cells were highly affected by unsolic acid and oleanolic acid.  
The MTT analysis results showed that total triterpenoids, oleanolic and unsolic acids exhibited remarkable inhibitory activity on proliferation of SK-Br-3, T47D and MCF-7 cells in vitro compared with the positive control. With increasing concentration, the inhibitory effect was enhanced. The IC\({}_{50}\) values (\(\upmu\)M) of total triterpenoids and the previously isolated two triterpenoids on SK-Br-3, T47D, and MCF-7 cells have been tabulated in Table 2. The results confirmed that unsolic acid exhibited significant antiproliferative activity against T47D and MCF-7 cells with IC\({}_{50}\) values of 1.63 \(\pm\) 0.62 and 6.62 \(\pm\) 1.09 \(\upmu\)M respectively, while the IC\({}_{50}\) values of doxorubicin was 9.0 \(\pm\) 1.2 and 6.7 \(\pm\) 0.9 \(\upmu\)M, respectively. Triterpenoids, after purification, showed IC\({}_{50}\) values of 5.91 \(\pm\) 0.98, while oleanolic acid showed cytotoxic activity against SK-Br-3 cancer cells with an IC\({}_{50}\) value of 3.08 \(\pm\) 0.83 \(\upmu\)M and an IC\({}_{50}\) value of 2.63 \(\pm\) 0.78 \(\upmu\)M against T47D cancer cells. From these results, it appeared that total triterpenoids showed best inhibition activity against the SK-Br-3 cancer cells in comparison to pure unsolic acid, oleanolic acid, and the positive control. This might be due to some synergistic effect among the components of the total triterpenoids against the SK-Br-3 cancer cells while such type of synergism has not been observed in the case of other two cell lines. The dose-response curves for inhibition of three human breast cancer cells of the screened compounds are shown in Figure 5. Ursolic acid is widely distributed in fruits and vegetables, and has shown the ability to inhibit proliferation of breast tumor cells, induce apoptosis, scavenge free radicals, as well as regulate several anti-apoptotic proteins. Ursolic acid is known for its anti-inflammatory and antioxidant activities as well as cytotoxic activities on several human breast cancer cell lines [26]. Ursolic acid administration was found to induce autophagy and apoptosis via the GSK and Bcl-2/Caspase-3 signaling pathways, and the inhibitory effect of unsolic acid on the inflammatory response was also involved in this mechanism. The authors mentioned that these results support the promise of unsolic acid as a potential chemotherapeutic agent for breast cancer [27].  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Cells**} & \multicolumn{4}{c}{**IC\({}_{50}\) Values (\(\upmu\)M)**} \\ \cline{2-5}  & **Total Triterpenoids** & **Ursolic Acid** & **Oleanolic Acid** & **Positive Control (Doxorubicin)** \\ \hline SK-Br-3 & 5.91 \(\pm\) 0.98 & 28.62 \(\pm\) 2.46 & 3.08 \(\pm\) 0.83 & 13 \(\pm\) 1.19 \\ T47D & 12.31 \(\pm\) 1.18 & 1.63 \(\pm\) 0.62 & 2.63 \(\pm\) 0.78 & 9.0 \(\pm\) 1.2 \\ MCF-7 & 13.91 \(\pm\) 1.36 & 6.62 \(\pm\) 1.09 & 28.22 \(\pm\) 2.34 & 6.7 \(\pm\) 0.9 \\ \hline \hline \end{tabular}
\end{table}
Table 2: The IC\({}_{50}\) values (\(\upmu\)M) of total triterpenoids after purification, unsolic and oleanolic acids from the _D. heterophyllum_ against SK-Br-3, T47D, and MCF-7 cells.