## 3 Results and Discussion
### Ethanol-Water Extraction and Optimization  
#### 3.3.1 Ethanol-Water Extraction  
Results of the ethanol-water extraction experiments are shown in Table 6.  
It was found that for the five replicates of the center point (runs 1, 2, 5, 6 and 9), the polyphenol content and antioxidant activity in the ethanol-water extracts showed low dispersion: 12.64 \(\pm\) 0.53 mg GAE/g (d.b.) and 37.93 \(\pm\) 2.07 mM trolox/g (d.b. ), respectively. On the contrary, the inulin content showed higher variability (5.11 \(\pm\) 2.92 mg glu eq/g (d.b. )), probably due to the presence of ethanol in the extraction media. These results show that TPC in ethanol-water extracts was slightly lower than values obtained for water extracts. However, there was a significant difference in terms of inulin content in both types of extracts, in such a way that the presence of ethanol in the extracting media significantly reduced the inulin extraction. According to the ANOVA shown in Table 7, it was found for TPC that all single factors were significant with a 95% confidence level. The response surface for the TPC is shown in Figure 2a. For a confidence level of 95%, quadratic effects of ethanol concentration and temperature are significant for TPC (Figure 2a). In view of the response surface shown in Figure 2b, TPC in the extracts decreases with ethanol concentration and increases with temperature. This tendency is in agreement with results obtained by other authors that used mixtures of ethanol-water for polyphenol extraction, so that the ethanol's presence promotes the higher extraction of polyphenols; however, from a maximum ethanol concentration, dependent on the food matrix, the extraction yields decrease [38; 39; 40]. The optimum value of TPC would be 22.64 mg GAE/g artichoke (d.b.) for the experimental conditions with an ethanol concentration of 2.0% (\(w/w\)), 360 min and 90.0 \({}^{\circ}\)C. The response surface in Equation (7) explains 96.1% of the total variability (r\({}^{2}\) = 96.1%; r\({}^{2}\)(adj) = 92.3%). \[\begin{split}&\text{TPC (mg ac.gallic eq/g(d.b. ))}\\ &\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad =12.351+0.0558\cdot\text{EtOH}-0.1466\cdot\text{T}+0.0237 \cdot\text{t}-0.0014\cdot\text{EtOH}^{2}-0.0003\cdot\text{EtOH}\cdot\text{T}- 0.0001\\ &\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad \quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad \quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad \quad\quad\quad\quad\In Figure 2d is shown the response surface for the antioxidant activity. It has been found that the optimized Aox would be 43.08 mM trolox/g artichoke (d.b.) for the experimental conditions with a 22.5% ethanol concentration, 200 min and 44 \({}^{\circ}\)C. Table 7 and Figure 2c show that the quadratic effects of EtOH concentration and temperature, and their combination, are significant (\(p<0.95\)). The experimental data were fitted to Equation (8) and explained 93% of the total variability (r\({}^{2}\) = 93.2%; r\({}^{2}\)(adj) = 86.4%). \[ \begin{array}{c}\text{Aox (mM trolox/g(db))}\\ =15.9372-0.0398\cdot\text{EtOH}+0.9376\cdot\text{T}+0.0672\cdot\text{t}-0.0071 \cdot\text{EtOH}^{2}+0.0073\cdot\text{EtOH}\cdot\text{T}+0.0002\\ \cdot\text{EtOH}\cdot\text{t}-0.0125\cdot\text{T}^{2}+0.00006\cdot\text{T}\cdot \text{t}-0.00018\cdot\text{t}^{2}\end{array}  \tag{8}\]Regarding the inulin content in ethanol-water extracts, linear and quadratic effects for temperature and the mixed effect with EtOH concentration-temperature were shown for a confidence level of 95%, significant regarding the inulin content (Figure 2e). Equation (9) explains 81% of the total variability (r\({}^{2}\) = 80.5%; r\({}^{2}\)(adj) = 61.0%) The response surface is shown in Figure 2f. The expected optimum value of inulin content in the studied range of time and temperature is 49.06 mg glu eu/g artichoke (d.b.) for the experimental conditions with a 0.2% ethanol concentration, 90 \({}^{\circ}\)C and 30 min. Inulin content (mg gluc eq/g (d.b.))