## 4 Conclusions  
This work presents, for the first time, an efficient and sustainable extraction method based on the use of NaDES, in combination with UAE, for NEPs' release from the extraction residue of mangosteeen peel. After the screening process, solvents such as ChCl:LA (1:2) and ChCl:EG (1:2) were selected due to their high PA contents and antioxidant capacities. In addition, the molar ratios of the components acting as HBAs and HBDs in the NaDES were studied, and ChCl:LA with a 1:2 molar ratio was chosen because this NaDES created extracts with higher antioxidant and PA contents. The use of the Box-Behnken experimental design allowed the investigation of the influence of the percentage of water in the extraction solvent, the ultrasound amplitude, and the extraction time upon the release of NEPs from the matrix. The optimal extraction conditions to recover NEPs by UAE, with ChCl:LA (1:2) as the extraction solvent, were a percentage of water of 18.8% (\(v/v\)), an ultrasound amplitude of 60%, and 15 min extraction time. This method was suitable to extract NEPs with high antioxidant capacity from the extraction residue of mangosteeen peel, presenting extracts with a higher PA content, antioxidant capacity, and number of phenolic compounds than the extracts of EEPs obtained from mangosteeen peel through the conventional extraction method. Moreover, the optimized extraction method enabled the recovery of phenolic compounds with higher molecular weights than the conventional extraction method. Therefore, the developed green method seems to be a promising tool for the extraction of antioxidant NEPs from mangosteeen peels. The following are available online at [[https://www.mdpi.com/article/10.3390/app11125625/s1](https://www.mdpi.com/article/10.3390/app11125625/s1)]([https://www.mdpi.com/article/10.3390/app11125625/s1](https://www.mdpi.com/article/10.3390/app11125625/s1)), Table S1: Experimental design obtained by [PERSON] and total PA content (DMAC and butanol/HCl assays) and antioxidant capacity (FRAP assays and hydroxyl assays, scavenging capacity of ABTS radicals, and capacity to inhibit the formation of hydroxyl radical assays) of the extracts obtained under the established conditions for the extraction of NEPs from mangosteeen peel using UAE with ChCl:LA (1:2); Table S2: Coefficients of the multiple linear regression models obtained for UAE with ChCl:LA (1:2) that best fitted the responses (total PA content (DMAC and butanol/HCl assays) and antioxidant capacity (FRAP assays and hydroxyl assays, scavenging capacity of ABTS radicals, and capacity to inhibit the formation of hydroxyl radical assays)) with extraction parameters A: water percentage; B: ultrasound amplitude; and C: time) as well as analysis of variance (ANOVA). Conceptualization, M.P. and M.L.M. ; Methodology, M.P. and M.L.M. ; Validation, M.P. and C.S. ; Formal analysis, M.P. and G.D.-R.; Investigation, C.S. and G.D.-R.; Resources,  
Figure 5: Effects of the extracts diluted with milli-Q water at four different concentrations (0.025-0.500 mg/mL), obtained under optimal extraction conditions (60% ultrasound amplitude, 18.8% water percentage, and 15 min extraction time) by UAE, with ChCl:LA (1:2) as the extraction solvent, from the extraction residue of mangosteeen peel (blue color), as well as the effects of NaDES diluted with the same amount of milli-Q-water as the extracts (orange color) on _cell viability_ in HeLa cells. M.P. and M.L.M. ; Data curation, C.S. and G.D.-R.; Writing--original draft preparation, M.P., G.D.-R. and C.S. ; Writing--review and editing, M.P. and M.L.M. ; Visualization, M.P., C.S. and G.D.-R.; Supervision, M.P. and M.L.M. ; Project administration, M.P. and M.L.M. ; Funding acquisition, M.P. and M.L.M. All authors have read and agreed to the published version of the manuscript.