## 4 Discussion
The total phenolic compounds were higher in peel extract obtained under the best conditions (9558 \(\pm\) 522 mg GAE/100 g DW) compared to the peel characterization (100 \(\pm\) 3.35 mg GAE/100 g DW). For the antioxidant capacity by ABTS assay and total monomeric anthocyanin level, higher values were also observed (0.246 \(\pm\) 0.00 mmol TEs/g, 60.3 \(\pm\) 0.3 mg C3G/100 g, respectively) on the extract than those obtained for the peel (0.203 \(\pm\) 0.027 mmol TEs/g, 19.723 \(\pm\) 2.689 mg C3G/100 g). This is expected for an extract obtained under the conditions mentioned above; however, here it is observed that the differences between the peel and the extract were not significant for the determination of antioxidant capacity (\(p\) = 0.107) and total phenols (\(p\) = 0.400), while for the concentration of total monomeric anthocyanins (\(p\) = 0.001), the difference was significant, considering the \(p\)\(\leq\) 0.01 value as statistically significant. To determine if the differences between the results were significant, the Student's t-test was performed. Both peel and other fruit residues as seed were studied for anthocyanin extraction. For mangosteen seed and _Nephelium lampaceum_ L. peel 23.5 mg C3G/100 g and 10.3 mg C3G/100 g, respectively, were found [44; 45]. However, for other sources, such as jaboticaba, eggplant, or red araca, the values were higher. In some cases, values are even four times greater [10; 11; 12; 46; 47; 48]. In the epicarp of _S. odorifera_, a value of up to 24 mg per gram on DW higher has been reported [5] compared with our results (60.3 \(\pm\) 0.3 mg C3G/100 g); however, these differences, in addition to the influence of the species, the section of the fruit used, the test conditions, or the anthocyanin quantification methods, can influence the results. In this work, a standardized technique has been used for the quantification of total monomeric anthocyanins for the characterization of native fruits [23]. Despite this, these results show the potential of \"kurugua\" peel as an important anthocyanin source for food applications, where otherwise it would be considered as waste, in addition to the contribution of flavonoids observed in the phytochemical profile of the extract (Table 7). It should be noted that this work addressed the optimization of the total phenol compounds and anthocyanin extraction system; however, future studies should prove its effectiveness for food applications as a dye additive and the technological implications that this would entail. It is important to promote a comprehensive use of _S. odorifera_ fruits, which otherwise may be lost. From this data, a value chain could be generated for its industrial applications in foodstuffs and medicine. Studies addressing the phenolic profile of _S. odorifera_ are still scarce; however, those available in the literature reported the occurrence of anthocyanins and flavonoid glycosides, in agreement with our results [2; 5]. Three anthocyanins were previously isolated and fully characterized in the peels of this fruit, including cyanidin-3-O-rutinoside, cyanidin-3-O-glucose, and peonidin-counaroyl-glucose [2]. In addition, pelargonidin-O-deoxyhexosyl-hexoside was tentatively identified in the epicarp [5]. These compounds were also detected in our samples except for the peonidin derivative. We observed malvidin mannose shikimate and another cyanidin rutinoside isomer, as opposed to previous reports. This malvidin derivative was observed in Chilean native berries from the _Ribes_ genus [49] and is reported for the first time in _S. odorifera_ samples. The chromatographic profile of the peel extracts from the Paraguayan _S. odorifera_ showed intense signals of flavonoids, including quercetin and kaempfer derivatives (Figure 5). The most significant was quercetin rutinoside, also reported in this species for specimens from Colombia and Brazil [2; 5]. Other flavonoids informed in this work, such as quercetin hexoside succinate and kaempfer aglycon, to the best of our knowledge, are reported for the first time in this species.