## 3 Results and Discussion
### Optimization of MAE Extraction Conditions  
#### 3.2.1 Optimization of Extraction Conditions for the Content of Total Compounds  
The effect of optimization of temperature, time and % of ethanol amount on the content of the total compounds was analyzed by response surface methodology (RSM). Table 2 shows the results of the ANOVA test of the regression model for the response variable (total compounds). The data revealed that the value of the determination coefficient (R\({}^{2}\)) was 97.03%. This result explained a considerable part of the variance within the data. The proof of the lack of fit is a function of determining the model. The test is performed by comparing the variability of the residuals in the current model with the variability in the observations under repeated conditions of the factors. Lack of fit for this model has a \(p\)-value greater than 0.05 (\(p\) = 0.1716). Therefore, the model seems to be adequate for the data observed at the 95.0% confidence level. ANOVA partitions the variability of total compounds into separate pieces for each of the effects. Then it tests the statistical significance of each effect by comparing its average square against an estimate of the experimental error. In this case, temperature (X\({}_{1}\)) (\(p\) = 0.0043), % EtOH (X\({}_{2}\)) (\(p\) = 0.0069), the quadratic effect of the temperature (X\({}_{11}\)) (\(p\) = 0.0082) and quadratic of time (X\({}_{33}\)) (\(p\) = 0.0198) had significant effects on the response variable (\(p\)-value less than 0.05, indicating that they were significantly different from zero with a confidence level of 95.0%). Response surface plots show the effect of two MAE parameters on the total content of compound while keeping the third parameter constant, and these are displayed in Figure 2. Figure 2a shows the positive effect of temperature and percentage ethanol on the total compounds, with the highest content appearing at 100-150 \({}^{\circ}\)C and 80-100% EtOH, while Figure 2b shows the maximum value of total compounds at 100-150 \({}^{\circ}\)C and 10-30 min. Finally, Figure 2c shows the effect of EtOH with time, with the highest content appearing in the range of 15-30 min and 95-100% EtOH. The fitted equation of the model for total compounds with the significant MAE parameters of X\({}_{1}\) (temperature), X\({}_{2}\) (% EtOH), X\({}_{11}\) (quadratic of temperature) and X\({}_{33}\) (quadratic of time) can be seen below. The fitted equation of the model includes the effect of time (X\({}_{3}\)) (Equation (1)):  
\[ \begin{array}{c}\text{Total compounds}=-57.8562+1.55431\text{X}_{1}+0.231443 \text{X}_{2}+1.38944\text{X}_{3}-0.00630364\text{X}_{11}-\\ 0.0330993\text{X}_{33}\end{array}  \tag{1}\]  
Considering the equation to explain the model for total compounds behavior and understanding the influence of each independent variable, an optimization of the conditions to obtain the highest content of total compounds was proposed under the following optimized conditions: 123 \({}^{\circ}\)C, 100% EtOH and an extraction time of 23 min to obtain a predictable value of 75.60 mg g\({}^{-1}\) d.w. of total compounds. To verify the suitability of the model for total compounds, the predictable value of total compounds was compared with experimental values obtained at optimal conditions. The theoretical and experimental values were 75.60 mg g\({}^{-1}\) d.w. and 86.7 \(\pm\) 0.4 mg g\({}^{-1}\) d.w., respectively. Analysis of the results revealed an acceptable variance (CV = 9.72%) between the theoretical and experimental data, therefore, the model was considered suitable.