## 3 Results
### Extraction Yield and Extraction Efficiency
Although the high temperatures would improve the diffusivity of the solvent and break component-matrix interactions, which increase the solubility of the analytes and consequently enhance the extraction yields [27], it does not necessarily mean a greater recovery of phenolic compounds. This fact seems to occur with artichoke by-products, which could be related to different factors. Indeed, an excessive increase in temperature is demonstrated to negatively affect the extraction of thermolabile compounds, such as phenolic compounds [26]. In addition to the possible thermal degradation of compounds, different combinations of solvent composition and temperature provide changes in the dielectric constant value, which is crucial for the extraction recovery of the phytochemicals from natural sources. In this way, special attention has to be paid to PLE 1 condition (120 \({}^{\circ}\)C, 100% EtOH) with a dielectric constant value of 19. Despite this condition reported the lowest yield, the recovery of phenolic compounds was higher compared to other PLE conditions. This phenomenon has also been reported in other plant matrices extracted by PLE at the same conditions (100% EtOH and 120 \({}^{\circ}\)C) [23]. Thereby, PLE 1 condition provided 2.6, 7.6, and 3.4 times higher recovery of phenolic acids, flavonoids, and total phenolic compounds than PLE 8 (120 \({}^{\circ}\)C, EtOH 0%, dielectric constant 50.4), respectively. Analyzing individual phenolic compounds identified in both PLE conditions, significant differences could be observed concerning the abundance of all of them (see Table S2). A similar trend was observed when the yield and recovery of phytochemical compounds of PLE 6 (120 \({}^{\circ}\)C, EtOH 50%, dielectric constant 34.7) were compared to those obtained for PLE 1 (120 \({}^{\circ}\)C, EtOH 100%, dielectric constant 19.0). Thus, the yield obtained for PLE 6 is 5.4 times higher than for PLE 1. Nevertheless, PLE 1 condition showed 2.6 times higher phenolic recovery than PLE 6. Nonetheless, tt is important to remark that at dielectric constant values higher than 19, minor differences were observed on the yield and recovery of phenolic compounds among the experimental conditions. Indeed, PLE 8 (dielectric constant value, 50.4) obtained an extraction yield 1.1 times higher than PLE 6 (dielectric constant value, 34.7). Moreover, PLE 6 had 1.1, 2.2, and 1.3 times higher recovery of phenolic acids, flavonoids, and total phenolic compounds than PLE 8, respectively, significant differences among all the characterized phenolic compounds were found for PLE 8 and PLE 6, except for chlorogenic and rosamarinic acids (Table S2). Therefore, similar differences on the yield and phytochemical recovery were also observed for PLE conditions where the same temperature was applied in combination with different percentages of ethanol, which consequently provides different values of dielectric constants. Some examples are: (a) temperature of 63 \({}^{\circ}\)C combined with 15% of ethanol (PLE 9, dielectric constant value 59.1) or 85% of ethanol (PLE 4, dielectric constant 31) and (b) extractions at 176 \({}^{\circ}\)C using 15% EtOH (PLE 5, dielectric constant 33.4) or 85% EtOH (PLE 2, dielectric constant 21.6). These results pointed out that at the same working temperature, the recovery of phenolic compounds is improved when the solvent composition (% EtOH) provides the lowest value of dielectric constant. Nevertheless, despite this focus in the targeted extraction of individual compounds provided by concrete PLE parameters, the total extraction yield should be considered if the main purpose is to obtain the maximum quantity of extract with a particular compound.