## 2 Results and Discussion
### Optimum Extraction Yield and Total Phenolic Content
The \(p\)-values were also used to check the significance of each coefficient and display the interaction pattern between the variables. It can be seen from Table 2 that the linear terms for temperature and extraction time were statistically significant (\(p<0.05\)) and played an important role in the extraction yields for both parts of \(O\). _mutabilis_. The same applies to the combined parameters (AB, BC, AC); however, the quadratic terms were all statistically insignificant, and can therefore be omitted from Equations (1) and (5). Furthermore, the reproducibility of the model was tested using the coefficient of variation (CV), which is the ratio of the standard error of estimate to the mean value of the observed response (given as percentage). The CV values of 4.15 and 7.57% for the aboveground part and roots, respectively, indicate a highly reproducible model. The contour plots and the corresponding 3D views provide a valuable insight on the combined influence of the independent variables and their effect on the dependent variable. Figure 1a-c correspond to the extraction yields obtained from the aboveground part. Figure 1a shows that at the lowest temperature of 100 \({}^{\circ}\)C, increasing the extraction time had practically no influence on the extraction yield, whereas at the highest temperature of 200 \({}^{\circ}\)C, increasing the extraction from 30 to 180 min resulted in \(\sim\)20% raise in extraction yield. This is an indication that extraction at this temperature is not so much kinetically driven as it is thermodynamically. Figure 1: \(Cont\). Figure 1: _Cont._  
In Figure 1b, the rate-determining influence of temperature can be seen again. At the lowest temperature of 100 \({}^{\circ}\)C, increasing the water/plant ratio inside the reactor from 0.1 to 0.4 reduced the extraction yield by \(\sim\)15%. A possible explanation for this is the participation of the water molecules in oxidation and degradation reactions for the extracted components. The opposite trend was observed at the highest temperature of 200 \({}^{\circ}\)C, where increasing the water/plant ratio from 0.1 to 0.4 increased the extraction yield by approximately 15%. At these conditions, the water molecules still participated in degradation reactions; however, the rate of extraction surpassed the rate of degradation, resulting in a net raise in the extraction yield. The combined influence of extraction time and water/plant ratio (Figure 1c) was less significant compared to the ones shown earlier. At the lowest water/plant ratio of 0.1, increasing the reaction time from 30 to 180 min had a minimal effect on yield, whereas at the highest water/plant ratio the effect of increasing the reaction time was dramatic, resulting in \(\sim\)20% higher yield. This observation may be attributed to the fact that more water molecules were able to penetrate the plant matrix and extracted a higher number of components, which masked potential degradation side-reactions. However, a smaller number of water molecules meant a reduced degree of interactions with the solutes and combined with the degradation caused by the longer extraction times, resulting in a lower extraction yield. Figure 1d-f correspond to the extraction yield obtained from the roots of the plant. In a similar manner to the aboveground part, increasing the temperature from 100 to 200 \({}^{\circ}\)C at each and all extraction times, increased the extraction yield by 30% (from \(\sim\)40 to \(\sim\)70%, Figure 1d), confirming the critical role of temperature. Regardless of temperature, a longer extraction time had minimal impact on the extraction yield. A similar pattern was observed in the interaction between temperature and water/plant ratio (Figure 1e). At each and all water/plant ratios, increasing the temperature from 100 to 200 \({}^{\circ}\)C resulted in more than double the extraction yield (30 to \(\sim\)62%). This indicates that in the studied range, the number of water molecules did not play a significant role and temperature was the rate-determining parameter.