## 3 Results and Discussion
### Selection of the Molar Ratio of the NaDES Components
These results highlighted that after conventional extraction, many antioxidant phenolic compounds were still retained in the extraction matrix, which were underestimated when the extractable polyphenols were extracted. Moreover, the molecular weight distribution of NEPs and EPPs recovered by optimal UAE-NaDES and conventional extraction methods from mangosteeen peels, respectively, were estimated by HPLC-SEC to learn the molecular weight of the released phenolic compounds [44]. Figure 3A,B displays both chromatograms at the same concentration (50 mg sample/mL), obtained for the extracts of NEPs and EPPs, respectively. The molecular weight distribution of the NEP extracts showed that the optimal UAE-NaDES method released phenolic compounds with high (6900-7500 Da), medium (2000-3000 Da), and low (<100 Da) molecular weights (Figure 3A). However, the extracts obtained by the conventional extraction method showed two chromatographic peaks, one of high molecular weight (7100 Da) and the other of low molecular weight (<100 Da) (Figure 3B). The extracts obtained by conventional extraction from mangosteeen peel displayed higher amounts of the compounds of <100 Da, while the optimal extraction method, based in UAE with ChCl:LA (1:2), allowed the release of NEPs with higher molecular weights. \begin{table}
\begin{tabular}{c c c c} \hline  & **Water Percentage** & **Ultrasound** & **Extraction Time** \\  & **(\%)** & **Amplitude (\%)** & **(min)** \\ \hline UAE optimal extraction conditions & \(18.8\) & 60.0 & \(15.0\) \\ \hline
**Response Variables** & **UAE Theoretical** & **UAE Experimental** & **Conventional** \\  & **Values** & **Values** & **Extraction** \\ \hline DMAC (mg epicatechin/100 g sample) & 219.95 & 238 \(\pm\) 21 & 2.4 \(\pm\) 0.2 \\ Butanol/HCl (mg epicatechin/100 g sample) & 102,200 & 37,638 \(\pm\) 6389 & 1017 \(\pm\) 57 \\ Scavenging capacity of ABTS radicals (\%) & 105.57 & 113 \(\pm\) 10 & 14 \(\pm\) 1 \\ Hydroxyl radicals (\% of hydroxyl radical inhibition) & 61.14 & 66 \(\pm\) 9 & 5.0 \(\pm\) 0.4 \\ FRAP (mg GSH/g sample) & 153.28 & 283 \(\pm\) 17 & 1.58 \(\pm\) 0.08 \\ \hline \end{tabular}
\end{table} 
Table 4: Optimal extraction conditions (percentage of water, ultrasound amplitude, and extraction time) to release antioxidant NEPs from the extraction residues of mangosteeen peels by UAE with ChCl:LA (1:2). Theoretical and experimental values of total PA content (DMAC and butanol/HCl assays) and total antioxidant capacity (scavenging capacity of ABTS radicals, capacity to inhibit the formation of hydroxyl radicals, and FRAP methods) obtained under optimal UAE conditions as well as the results on the extraction of EEPs using a conventional extraction method. On the other hand, the phenolic profiles of the extracts obtained by the optimal UAE-NaDES and conventional extraction methods were also analyzed by reverse-phase HPLC-DAD. Figure 4 shows the chromatograms obtained at the same concentration (50 mg sample/mL), which demonstrate that many phenolic compounds were retained in the extraction residue after the conventional extraction of mangosteen peel. The DAD spectra analysis of the separated compounds allowed the classification of phenolic compounds by family groups. For instance, the selected wavelengths of 280, 360, and 510 nm made possible the identification of phenolic compounds, flavonoids and xanthones, and anthocyanins, respectively [59]. Six anthocyanins, 4 flavonoids, 7 xanthones, and 8 phenolic compounds (phenolic acids) were found in the extracts of NEPs (Figure 4A). The extract obtained by conventional extraction methods presented 4 xanthones (Figure 4B). Therefore, the comparison of both extracts at the same concentration revealed that the developed extraction method to release NEPs from the extraction residue of mangosteen was more efficient for extracting phenolic compounds than the conventional extraction method for recovering EPPs from mangosteen peel.