## 4 Discussion
### Cytotoxicity  
When the LC\({}_{50}\) is 0.02 mg/mL or lower, a plant extract is classified as cytotoxic [32]. Based on the above definition, all the tested plant extracts in this study were relatively non-cytotoxic as the lowest value obtained was 0.08 mg/mL (Table 9), which is above the cut-off value.  
However, another study reported the LC\({}_{50}\) of acetone and ethanol extracts of _S. lancea_ extracts to be below 0.05 mg/mL, which is lower compared to the values obtained in this work [41]. They observed that the acetone and ethanol extracts of _S. lancea_ exhibited moderate toxicity toward Vero cells at concentrations of 0.25 and 0.05 mg/mL, respectively. In contrast, the ethyl acetate extract of _S. lancea_ showed no toxicity at the same concentrations. Therefore, they hypothesized that the presence of alkaloids and saponins in _S. lancea_ could be responsible for its observed toxicity [41]. LC\({}_{50}\) values of 0.025, 0.022, and 0.051 mg/mL against Vero cells by other species of the _Searsia_ genus, such as _S. leptodictus, S. pendulina_, and _S. pentheri_, respectively have been reported [42]. Moreover, the cytotoxic activity of water extracts of _S. lancea_ leaf material has been reported against brine shrimp with LC\({}_{50}\) value of 0.6 mg/mL [43].  
According to reports, the n-hexane and ethyl acetate extracts derived from the root bark of _E. caffe_ demonstrated cytotoxic effects on human cervical carcinoma cells at concentrations of 0.11 mg/mL and 0.06 mg/mL, respectively [44]. Another study found that the ethanol extract of the stem bark of _A. venosum_ exhibited greater toxicity (LC\({}_{50}\) = 0.026-0.041 mg/mL) compared to the root extract (LC\({}_{50}\) = 0.063-0.080 mg/mL) against brine shrimp [45]. However, it should be noted that in vitro cellular toxicity may not necessarily reflect in vivo toxicity due to various factors, such as gut interactions and bioavailability. Therefore, further studies involving acute and chronic animal toxicity testing are necessary to confirm the safety of these plant extracts [42]. The LC\({}_{50}\) of ethanol extracts of the plants in this study were higher than those of their acetone counterparts, which suggests that the ethanol extracts are relatively less toxic compared to their acetone counterparts. The results obtained by [45] also favor ethanol extracts over acetone extracts. This is significant for potential commercialization as ethanol is preferred as a solvent for industrial use since it is less flammable and dangerous to work with in large quantities.  
To determine the safety margin of a plant extract, the selectivity index (SI) is calculated using two variables: Cytotoxicity (mg/mL) and minimum inhibitory concentration (MIC) values [46]. If the selectivity index (SI) value is greater than 1, it indicates that the plant extract is more harmful to the pathogen than to the mammalian cells tested for cytotoxicity. A higher SI value is more encouraging since it suggests that the plant extract's activity is not due to general toxicity. Consequently, the higher the SI, the greater the potential for the plant extract to be developed into a safe herbal product. The acetone extracts of _S. lancea_, which showed the most promising antibacterial activity against all the organisms tested, also had a very promising LC\({}_{50}\) value of 0.15 \(\pm\) 0.02, SI range of 2.14 to 10.23, and mean SI of 4.69 \(\pm\) 0.89. Based on the results obtained, it can be concluded that although the extracts of all three plants tested have the potential to be developed as safe and effective herbal remedies for treating microbial infections, _S. lancea_ seems to be the most promising candidate.