## 4 Extraction Methods
### Extraction in Supercritical Fluids
#### 4.1.1 Solvent Selection--Efficiency
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Solvent** & \begin{tabular}{c} **Critical** \\ **Temperature** \\ \end{tabular} & \begin{tabular}{c} **Critical** \\ **Pressure** \\ \end{tabular} & \begin{tabular}{c} **Density** \\ **(20 \({}^{\circ}\)C) [77]** \\ \end{tabular} & \begin{tabular}{c} **Critical** \\ **Density** \\ \end{tabular} & \begin{tabular}{c} **Dielectric** \\ **Constant** \\ \end{tabular} & \begin{tabular}{c} **Critical** \\ **Dielectric** \\ **Constant** \\ \end{tabular} & **Reference** \\ \hline \hline \begin{tabular}{c} **T\({}_{\text{c}}\)** [\({}^{\circ}\)**C]** \\ \end{tabular} & \(\mathbf{p_{c}}\) [MPa] & \(\mathbf{\rho_{c}}\) [g/cm\({}^{3}\)] & \(\mathbf{\rho_{c}}\) [g/cm\({}^{3}\)] & K [-] & \(\mathbf{K_{c}}\) [-] & \\ \hline \begin{tabular}{c} Carbon \\ dioxide \\ \end{tabular} & 31.1 & 7.38 & 0.00198 & 0.469 & 1.6 & \textless{}1.1 & [38; 43; 45] \\ \hline \begin{tabular}{c} Water \\ \end{tabular} & 374.3 & 22.12 & 0.998 & 0.348 & 78.36 & 5.35 & [78] \\ \hline \begin{tabular}{c} Methanol \\ \end{tabular} & 239.6 & 8.09 & 0.791 & 0.272 & 32.61 & \begin{tabular}{c} 8.40 \\ **(10 MPa, 218 \({}^{\circ}\)C)** \\ \end{tabular} & [79] \\ \hline \begin{tabular}{c} Ethanol \\ \end{tabular} & 240.9 & 6.14 & 0.789 & 0.276 & 24.85 & \
\begin{tabular}{c} 1.90 \\ **(244 \({}^{\circ}\)C)** \\ \end{tabular} & [80] \\ \hline
\begin{tabular}{c} Chloroform \\ \end{tabular} & 319.0 & 5.79 & 1.479 & 0.491 & 4.71 & n.a & [81; 82] \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Critical parameters of solvents used for the extraction of tannins. tannins at 60 \({}^{\circ}\)C and 20 MPa, was water. Some polyphenols, especially flavonoid aglycones and phenolic terpen, are poorly soluble in water and require organic solvents [79, 88]. Therefore, chloroform was also used for tannin extraction among the abovementioned solvents under supercritical conditions [75]. Chloroform is mainly used for the isolation of low-polarity lignans and glycosides. Many studies, especially those with a practical or industrial focus, prioritize the evaluation of antioxidant activity (AA) over the extraction yield. The antioxidant properties of polyphenolic compounds, particularly tannins, are a key aspect of their industrial relevance. These compounds are often added to materials such as polymers not only to enhance mechanical performance but also to improve oxidative stability [89]. This activity is commonly assessed using standardized assays such as DPPH ([2,2-di(4-tert-octylphenyl)-1-picrylhydrazyl]), FRAP (Ferric Reducing Antioxidant Power), TRAP (Total Peroxyl Radical Trapping Antioxidant Parameter), and ABTS (2,2'-Azinobis-(3 3-ethylbenzothazoline-6-sulfonic acid) [90, 91]. Notably, the antioxidant potential of polyphenols is closely linked to their chemical structure--extracts rich in flavonoid subunits generally exhibit higher AA [92]. In the study on jatoba, [PERSON] et al. demonstrate an increase in antioxidant activity (AA), along with an increase in extraction yield [47]. However, this activity can vary significantly, depending on the plant species, the specific plant part used, the growing conditions, and even the harvest season [65], as well as the extraction parameters (temperature, time, and pressure).