## 3 Results and Discussion
### NaDES Screening for the Extraction of NEPs from Mangosteen Peel
With ChCl:urea, no results could be obtained for the total PA content with DMAC assay because DMAC reacts with urea, this being a method that is also used to detect the presence of urine in samples [53]. Therefore, more-polar NaDES composed of organic acids such as lactic acid, formic acid, and citric acid extracted greater amounts of PAs than less-polar NaDES based on sugar and polyalcohol such as the NaDES composed of sorbitol [54]. In addition, organic acid-based NaDES were more acidic (pH < 3), and this medium favored the extraction of anthocyanins and other phenolic compounds as well as their stability [23]. These results suggested that many PAs remained retained on the extraction residue of mangosteen peels after the conventional extraction of EPPs. On the other hand, to evaluate the antioxidant capacity of extracts, ABTS and hydroxyl radical scavenging assays were employed. The advantage of using two different methods  
\begin{table} \begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**NaDES**} & **DMAC** & **Butanol/HCl** & **Hydroxyl Radical** & **\% Scavenging of** \\  & **(mg Epicatechin/100 g Sample)** & **(mg Epicatechin/100 g Sample)** & **(\% of Inhibition)** & **ABTS Radicals** \\ \hline ChCl:FA & \(18\pm 1\) \({}^{\text{b}}\) & \(1767\pm 197\) \({}^{\text{b}\text{c}}\) & \(71\pm 17\) \({}^{\text{a}}\) & \(41\pm 2\) \({}^{\text{d}}\) \\ ChCl:LA & \(25.4\pm 0.6\) \({}^{\text{a}}\) & \(2447\pm 237\) \({}^{\text{a}}\) & \(24\pm 5\) \({}^{\text{d}}\) & \(34\pm 2\) \({}^{\text{e}}\) \\ ChCl:sorb & \(5\pm 1\) \({}^{\text{f}}\) & \(759\pm 52\) \({}^{\text{d}}\) & \(58\pm 10\) \({}^{\text{b}}\) & \(49\pm 5\) \({}^{\text{c}}\) \\ ChCl:EG & \(9.2\pm 0.9\) \({}^{\text{e}}\) & \(623\pm 110\) \({}^{\text{e}}\) & \(39\pm 8\) \({}^{\text{c}}\) & \(65\pm 4\) \({}^{\text{a}}\) \\ ChCl:CA & \(15\pm 2\) \({}^{\text{d}}\) & \(1493\pm 72\) \({}^{\text{c}}\) & & \(25\pm 2\) \({}^{\text{g}}\) \\ ChCl:urea & & \(415\pm 57\) \({}^{\text{e}}\) & \(9\pm 4\) \({}^{\text{e}}\) & \(61\pm 2\) \({}^{\text{b}}\) \\ ChCl:gly & \(16.5\pm 0.5\) \({}^{\text{c}}\) & \(1954\pm 184\) \({}^{\text{b}}\) & \(10\pm 4\) \({}^{\text{e}}\) & \(30\pm 6\) \({}^{\text{f}}\) \\ \hline \hline \end{tabular}  Note: a:\({}^{\text{b}\text{c}\text{c}\text{d}\text{was that they could provide wider knowledge of the chemical composition of the extracts as well as their capacities against different radicals. The first assay measured the inhibition capacity of the ABTS**+** radical and was based on the electron transfer reaction, while the second assay evaluated the capacity to inhibit the formation of hydroxyl radicals and was based on the transfer of hydrogen atoms. Table 2 shows the results attained with these two methods for the extracts obtained from the residue of mangosteen peels by UAE with different NaDES. According to the ABTS assay, all extracts obtained by UAE with different NaDES presented significant differences in their antioxidant capacities (\(p\leq 0.05\)). The ChCl:EG extracts exhibited the highest antioxidant capacity (65% ABTS radical scavenging), followed by those corresponding to ChCl:urea (61% ABTS radical scavenging), ChCl:sor (49% ABTS radical scavenging), and ChCl:FA (41% ABTS radical scavenging). However, the ChCl:LA, ChCl:gly, and ChCl:CA extracts showed the lowest capacity to scavenge ABTS radicals (34, 30, and 25%, respectively) (Table 2). As can be observed in Table 2, the capacity to inhibit the formation of hydroxyl radicals of NEPs extracts from mangosteen peel ranged from 9 to 71%. For instance, the ChCl:FA extracts were the most active, showing an inhibition of hydroxyl radical formation of 71%, followed by ChCl:sorb with 58% and ChCl:EG with 39%. In addition, the extracts obtained with ChCl:LA, ChCl:gly, and ChCl:urea exhibited the lowest inhibition of the formation of hydroxyl radicals (9-24%). No significant differences were observed between the extracts of ChCl:gly and ChCl:urea (\(p>0.05\)). However, the extract obtained with ChCl:CA did not show antioxidant capacity with this assay.