## 3 Results and Discussion
### Comparison among the Soxhlet, Percolation, and Thermosonication Techniques  
Fennel extracts obtained by the Soxhlet and percolation techniques were compared with the fennel extract produced with the best thermosonication condition (300 W and 60 \({}^{\circ}\)C). Figure 5 exhibits the visual appearance of each extract. Thermosonication and percolation produced visually clearer and greener fennel extracts. The extract obtained by Soxhlet had a darker, brown color. In the Soxhlet technique, the fennel sample was exposed at boiling temperature for 6 h [26]. Thus, this extraction condition may promote thermal degradation of fennel compounds producing a darker extract [13]. Despite this, the fennel extract obtained by Soxhlet presented the highest global yield. Table 2 presents extraction yields acquired for each extraction technique. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Extraction Technique** & **Global Yield (g/100 g)** & **Extraction Yield of Solids (g/100 g)** \\ \hline Soxhlet & \(14\pm 1\)\({}^{\text{a}}\) & 0.021 \(\pm\) 0.001 \({}^{\text{c}}\) \\ \hline Percolation & \(7.5\pm 0.3\)\({}^{\text{b}}\) & 0.98 \(\pm\) 0.02 \({}^{\text{a}}\) \\ \hline Thermosonication & \(5.5\pm 0.1\)\({}^{\text{c}}\) & 0.73 \(\pm\) 0.02 \({}^{\text{b}}\) \\ \hline \hline \end{tabular} Global yield: g dried extract/100 g ground fennel; solids extracted yield: g dried extract/100 g fennel ethanolic extract. Mean values \(\pm\) standard deviation (\(n\) = 2). Values followed by different letters (a–c) in the same column show differences by [PERSON]’s test at 95\% significance (p\)-value \(\leq\) 0.05).  
\end{table} 
Table 2: Global and extraction yields. Figure 4: Thermosonication effects on the antioxidant activity of fennel extracts obtained by thermosonication using the (a) DPPH radical and (b) TEAC methods. Figure 5: The effect of different extraction techniques on the visual appearance of fennel extracts. The Soxhlet resulted in greater extraction of solids from the raw material. However, these solids were more diluted in the extract due to the greater amount of solvent used. Thus, this technique resulted in the highest global yield and the lowest solids' extraction yield (Table 2). The extraction by percolation produced an extract with higher global yield and extraction yield of solids than thermosonication. The higher global yields obtained by the Soxhlet and percolation techniques can be associated with the longer extraction times employed by them. The Soxhlet technique also extracted more phenolic compounds from fennel than both the thermosonication and percolation techniques. Figure 6 presents the results of TPC recovery from fennel by each extraction technique. The thermal energy provided by the Soxhlet and thermosonication extraction techniques may have favored the extraction of phenolic compounds since percolation uses the lowest and constant extraction temperature of 60 \({}^{\circ}\)C. Thermal energy favors the mass transfer by promoting an increase in the solubility of the solvent and mass transfer coefficients. Furthermore, Soxhlet employs a long extraction time with a longer contact time between solvent and solute. Despite this, the Soxhlet technique produced an extract with only 20% more phenolic compounds than thermosonication with just 20 min of extraction time. [PERSON] et al. [13] extracted the same content of phenolic compounds from black locust flowers using ultrasound and Soxhlet techniques. However, the ultrasound-assisted extraction was performed using an ultrasonic bath (40 kHz and 150 W) at 60 \({}^{\circ}\)C for 30 min. Thus, a longer extraction time by thermosonication could have produced an extract with a higher yield of phenolic compounds. The results obtained for the antioxidant capacity of the fennel extracts corroborated with that observed for TPC. Figure 7 presents the extracts' antioxidant activity measured by DPPH and ABTS assays. The extract obtained by the Soxhlet technique presented the highest antioxidant capacity.