## 3 Results
### Extraction Yield and Extraction Efficiency
Figure 3 draws the peak area (mean value \(\pm\) standard deviation) of the individual compounds detected in each arithoke PLE extract as well as the total phenolic acids and flavonoids (see Table S1). In regards to the total abundance of phenolic acids in the _C. scolymus_ PLE extracts, it could be observed that PLE 1 (120 \({}^{\circ}\)C, EtOH 100%), PLE 4 (63 \({}^{\circ}\)C, EtOH 85%), and PLE 7  
Figure 3: Abundance of phenolic compounds characterized in each _C. scolymus_ PLE extracts by HPLC-ESI-TOF-MS: (**A**) individual phenolic acids, (**B**) total phenolic acids, (**C**) individual flavonoids, and (**D**) total flavonoids. (40 \({}^{\circ}\)C, EtOH 50%) conditions showed the best recovery for this chemical sub-class. On the contrary, PLE 5 (176 \({}^{\circ}\)C, EtOH 15%) and PLE 2 (176 \({}^{\circ}\)C, EtOH 85%) present the worst extraction recoveries for this kind of substances. In light of these data, it can be concluded that higher percentages of ethanol in aqueous mixtures and moderate to high extraction temperature enhances the extraction of these compounds. On the contrary, very high temperatures, such as in PLE 5 and PLE 2, seem to act to the detriment of the extraction of phenolic acids. Additionally, the individual behavior of phenolic acids was also monitored. Chlorogenic acid was extracted in greater abundance by PLE 1 condition (with the highest percentage of ethanol, 100%), followed by PLE 4 (63 \({}^{\circ}\)C, EtOH 85%) and PLE 7 (40 \({}^{\circ}\)C, EtOH 50%) experiments, which presented similar abundances. In the case of rosamarinic acid, the best extraction conditions were PLE 7 and PLE 4. Both experiments were performed with low-intermediate temperatures and medium-high percentages of ethanol. In fact, higher temperatures such as the applied in PLE 5 (176 \({}^{\circ}\)C, EtOH 15%) recovered this compound in very low amount or could not extract rosamarinic acid from artichoke by-products, as in PLE 2 (176 \({}^{\circ}\)C, EtOH 85%) and PLE 3 (200 \({}^{\circ}\)C, EtOH 50%). Finally, within the family of phenolic acids, cynarin isomers showed different behavior over the tested extraction conditions. PLE 1 run (120 \({}^{\circ}\)C, EtOH 100%) reported a high value of cynarin isomer 1 peak area, while cynarin isomer 2 was not recovered in abundance. The same phenomena could be described for PLE 4 (63 \({}^{\circ}\)C, EtOH 85%) and PLE 7 (40 \({}^{\circ}\)C, EtOH 50%). On the other hand, the analysis of the total abundance of flavonoids in the artichoke extracts indicated that PLE 1 (120 \({}^{\circ}\)C, EtOH 100%) was the best condition, followed by PLE 4 (63 \({}^{\circ}\)C, EtOH 85%) and PLE 7 (40 \({}^{\circ}\)C, EtOH 50%). All these runs applied intermediate conditions within the range of temperature and percentage of ethanol as solvent combinations. On the contrary, the conditions PLE 2 (176 \({}^{\circ}\)C, EtOH 85%), PLE 5 (176 \({}^{\circ}\)C, EtOH 15%), PLE 8 (120 \({}^{\circ}\)C, EtOH 0%), and PLE 9 (63 \({}^{\circ}\)C, EtOH 15%) reported a lower abundance with respect to the other PLE extracts. Analyzing individual flavonoids, the highest abundance of glycoside structures was obtained under the conditions PLE 1 (120 \({}^{\circ}\)C, EtOH 100%) and PLE 4 (63 \({}^{\circ}\)C, EtOH 85%). On further consideration, aglycon flavonoids as luteolin and apigenin showed the same trend, being better extracted by the PLE 1 condition. The abundance of simple flavonoids, luteolin and apigenin, was not increased as extraction temperatures raised. This fact suggests that high temperatures did not generate the hydrolysis of glycoside forms over the extraction process (luteolin-glucose, apigenin-glucose, luteolin-rutinoside, and apigenin-rutinoside). Taking into account all these results, a comparison of the extraction yield and phenolic compounds recovery in each experimental PLE run showed important differences.