## 3 Results
### Selectivity Index of S. triloba Acetone Extract for U2 OS and SKOV3 Cells
By the law of mass action, the Dm is used to determine the combination index (CI) values. _S. triloba_ (ST); paclitaxel (PTX); _S. triloba_ + paclitaxel (ST-PTX); fraction of cells inhibited by treatment (Fa); fraction of cells uninhibited by treatment (Fu); dose (D). \begin{table}
\begin{tabular}{l l l l} \hline \hline
**Drug** & **Dm * (ug/mL)** & **m ** & **r *** \\ \hline _S. triloba_ & 50.9282 & 0.85854 & 0.9587 \\ Paclitaxel & 0.22062 & 1.1417 & 0.89187 \\ S. triloba + Paclitaxel & 13.8357 & 0.95052 & 0.91799 \\ \hline \hline \end{tabular} \({}^{*}\)median effect dose; \({}^{**}\) slope of the median-effect (ME) plot; \({}^{***}\) linear correlation coefficient of the ME-plot.  
\end{table} 
Table 4: Median effect dose for SKOV3 cells. S. triloba Acetone Extract Increases the Percentage of Non-Viable Cells in Both U2 OS and SKOV3 Cells  
Trypan blue exclusion assay was utilized to determine the percentage of non-viable U2 OS and SKOV3 cells upon exposure to _S. triloba_ acetone extract adjusted to respective IC\({}_{50}\) values. The percentage of non-viable cells after _S. triloba_ treatment increased by (17.758%) and (44.367%) for U2 OS and SKOV3 cells respectively; significant increases were, however, noted in SKOV3 cells only when compared with non-treated controls. Furthermore, the combination treatment that exhibited the greatest synergy induced a significantly higher increase (91.967%) in non-viable SKOV3 cells, and this surge was 19.48% greater than that induced by paclitaxel. Both cisplatin (IC\({}_{50}\)) and paclitaxel (IC\({}_{50}\)) served as positive controls for U2 OS and SKOV3 cells respectively (Figure 5). Figure 4: Logarithmic combination index plot and Log(DRI) plot for the drug combination experiment in SKOV3 cells. (**A**) A plot of Log(CI) against Fa was used to determine which concentrations of the drug combination exhibited synergy; a CI \(<\) 1, CI \(=\) 1 and CI \(>\) 1 indicates synergism, additive effect and antagonism, respectively. Only one out of six combinations exhibited synergy, all others were antagonistic. (**B**) A plot of Log(DRI) against Fa was used to calculate dose reduction indices (DRI) for the drugs used in the combined treatment. A DRI \(>\) 1 indicates that the dose of a given drug is reduced when used in combination than if it were used without combination. DRI values \(<\) 1 are not favorable for dose reduction. _S. triloba_ (ST); paclitaxel (PTX); _S. triloba_ + paclitaxel (ST-PTX); fraction of cells inhibited by treatment (Fa); combination index (CI), dose reduction index (DRI). Figure 5: _S. triloba_ acetone extract increases the percentage of non-viable U2 OS and SKOV3 cells. (**A**) When compared with non-treated controls, the number of non-viable U2 OS cells increased by 17.8% with no statistical significance. (**B**) Statistically significant results were, however, observed for SKOV3 cells, where the _S. triloba_ acetone extract (IC50) along with the combination treatment (_S. triloba_ (19 \(\mu\)g/mL) + paclitaxel (0.787 \(\mu\)g/mL)) induced an increase in non-viable cells of about 44% and 92% respectively. Both cisplatin (IC50) and paclitaxel (IC50) served as positive controls for U2 OS and SKOV3 cells, respectively, and cells were incubated for 48 h post treatment. Results are a representation of three independent experiments (***\(p\leq\) 0.001, ***\(p\leq\) 0.01, *\(p\leq\) 0.05).