## 2 Results and Discussion
### Antioxidant Activity
in the ORAC method, CET followed by MAE BE apple extracts showed the highest antioxidant activity in the ABTS method, which is positively correlated (R\({}^{2}\) = 0.9644) with the higher TPC reported above. Furthermore, this behaviour has also been reported by [PERSON] et al. [50] and [PERSON] et al. [51], who demonstrated a good correlation between total phenolic compounds and the antioxidant activity of melon peels and strawberry tree extracts, respectively, indicating that phenolic compounds are major contributors to antioxidant activity. In the results of DPPH free radicals inhibition, it was observed that MAE presented higher antioxidant activity (5.11 \(\pm\) 0.13 mg TE/g DE) (_p_ < 0.05), followed by CET (3.10 \(\pm\) 0.07 mg TE/g DE) (_p_ < 0.05), and CE (2.70 \(\pm\) 0.12 mg TE/g DE) and UAE (2.69 \(\pm\) 0.26 mg TE/g DE), which showed the lowest values (_p_ > 0.05). The values obtained in the DPPH method did not correlate with the TPC (R\({}^{2}\) = 0.4097). This could be due to the DPPH method being more efficient to measure less polar compounds, since these radicals only are dissolved in an organic solvent (in this work was used methanol) and therefore evaluates hydrophobic systems [52]. Instead observed in other two methods, in the DPPH method, MAE extract achieved higher values than the CET extract, and this could be explained by ORAC and ABTS radicals reacting energetically with hydrogen-donors, although DPPH is more selective in the reaction with hydrogen-donors than ABTS, which can interact greatly with some of the phenolic compounds recovered in greater quantity (CGAs, procyanidins and quercetin-3-rutinoside) that apparently possess a greater antioxidant capacity with this method [53]. The antioxidant values agree with the phenolic compounds present in each extract (HPLC values) since the extracts with more phenolic compounds (CET and MAE) shows more antioxidant activity than UAE and CE. Furthermore, the higher antioxidant activity of CET (in ABTS and ORAC method) could be related with the compounds more abundant in this extract ((+)-catechin, (-)-epicatechin, phloridzin and phloretin once molecules show high correlation with the ORAC method [2]. On the other hand, the MAE extraction could be a selective method to produce an extract with higher antioxidant activity and rich in CGAs and procyanidins, which are compounds well valued in the global functional food market and with human health benefits reported [9]. Therefore, it was suggested that the differences in BE extracts' antioxidant activity depend on the composition of polyphenolic compounds and the structure of some compounds, particularly the distribution of hydroxyl groups in the molecules. To our knowledge, there are no research studies about using non-compliant BE apples or other varieties to produce functional extracts with a proven antioxidant activity using green methodologies such as MAE and UAE and using CE extraction with ethanol and water mixtures. However, [PERSON] et al. [3] evaluated the antioxidant activity of BE apple dried powder (extract obtained with methanol 80% at 25 \({}^{\circ}\)C during 1 h) and reported a EC\({}_{50}\) = 0.71 \(\pm\) 0.05 mg/mL in DPPH assay and [PERSON] et al. [2] reported an ORAC value of 1503 \(\pm\) 48 \(\upmu\)mol TE/100 g for BE apple (extracted with acetone 80% at 25 \({}^{\circ}\)C during 8 min). These relevant results of antioxidant activity on BE apple extracts are in agreement with the higher content of polyphenol compounds and show the importance of using non-compliant fruit as a natural source of antioxidants. These \"ugly fruit\" are a low-cost resource that could be used to develop new food ingredients for the food industry, such as natural antioxidant extracts. On the other hand, the use of non-compliant fruit represents a solution with low environmental impact since it uses value-added food and promotes a sustainable bio-economy [42].