## 2 Results and Discussion
### Phenolic Compounds Profile and Quantification
Only three quercetin derivatives were identified among flavonols: quercetin-3-O-glucose, quercetin-3-O-rutinoside and quercetin-3-O-hexoside, where the first one was also detected in exotic and Portuguese varieties, for instance, in BE apple [1]. Furthermore, they report two more flavonoids: kaempfer-3-glucose and quercetin-3-rhamonside. Dihydrochalcones are one of the most recognized apple polyphenols group and two compounds from this group are detected in the extracts, phloretin and phlorelin. These compounds have been already reported in BE apple by [PERSON] et al. [3]. However, these compounds were only detected in the CET and MAE extracts. As previously mentioned, some of the extraction methodologies used to produce the different BE apple extracts showed no effectiveness in recovering some of the apple phenolic compounds, as LC-ESI-QqTOF-HRMS did not detect them in the extracts. For instance, in BE apple, the CE extract showed only eight phenolic compounds among the total 23 identified demonstrating the lower number of phenolic compounds present in the extract. The higher phenolic variability detected in MAE and CET extracts is consistent with the results obtained in TPC. The temperature increasing in conventional extraction (from 25 to 80 \({}^{\circ}\)C) had a positive impact in polyphenols extraction, since in CET the total 23 phenolic compounds were identified. Additionally, MAE extract showed also the same phenolic compounds identified. Thus, the CET and MAE reveal to be more promising methodologies for extraction of higher variability of phenolic compounds from BE apple. Regarding the UAE, the results were similar to CE, which corroborate the TPC values. Therefore, the compounds with higher intensity identified in each BE apple extract were quantified by HPLC-DAD, and are summarized in Table 3. The extracts obtained by CET and MAE, despite the differences observed in the amounts of each phenolic compound, exhibited a similar chromatographic profile, as expected, due to the previous identification reported. Instead, the extracts obtained by CE and UAE exhibited only a few phenolic compounds quantified. The major phenolics found in the extracts were chlorogenic acid, (--)-epicatechin, (+)-catechin, procyanidin B2 and C1, _p_-coumaroylquinic acid and phlorelin. All of them are usually reported in apples [32], mainly in BE variety [1,3]. The MAE extract had the highest contents of chlorogenic acid (0.48 \(\pm\) 0.07 mg/g DE), cryptochlorogenic acid (0.12 \(\pm\) 0.01 mg/g DE) procyanidin B2 (0.12 \(\pm\) 0.01), procyanidin C1 (0.12 \(\pm\) 0.01 mg/g DE (_p_ > 0.05). Additionally, no significant differences (_p_ > 0.05) were found between MAE and CET in terms of _p_-coumaroylquinic acid, _p_-coumaric, (+)-catechin, (--)-epicatechin-3-gallate, (--)-epicatechin and quercetin-3-rutinoside contents. Therefore, these phenolics variations are in accordance with the TPC results (Table 1), and no significant differences were observed between MAE and CET. Other compounds that occur naturally in apples and associated with several health-promoting effects are the dihydrochalcones phlorelin and phlorelin [33]. In this study, these compounds were only recovered by CET and MAE and were the only compounds found at the highest amount in CET than in MAE extract: phlorelin (0.21 \(\pm\) 0.03 mg/g DE) and phloretin (0.11 \(\pm\) 0.01 mg/g DE) (_p_ < 0.05). Usually,this dihydrohalcone is found in greater quantities in the peel than in flesh apple, and the amount of phloridzin is higher than phloretin [33], which are in agreement with our results. Previous works with BE apple polyphenols characterization reported only phloridzin in BE apple [1], although works of [PERSON] et al. [3] reported both phloridzin and phloretin. The application of conventional methods with higher temperatures (CET) involves longer periods at high temperature than MAE, leading to the possibility of oxidation and hydrolysis of phenolic compounds [34].