## 2 Results and Discussion
### Principal Component Analysis  
A principal component analysis (PCA) was performed to achieve an overall vision of the different extracts and identify a possible relationship between all parameters analyzed in this study. The variables considered in PCA for each extract are described in Table 4.  
In this analysis, 16 variables were measured in the different BE apple extracts and analyzed by a bidimensional plot (Figure 2). The cumulative percentage of the total variance explained by the first two components was 99.58%. Component 1, which described 87.71% of the parameters' variability, was positively influenced by all the variables in the study accounting for TPC, which was strongly associated with this component as well p-coumaric, ABTS method and ORAC method. In component 2, which accounted for 11.87% of the variability, received the main positive contribution from the DPPH method, cryptochlorogenic and chlorogenic acid andprocyanidin C1. Through the analysis of Figure 3, it was possible to verify that the TPC (variable 1) is more correlated with ABTS (variable 2) and ORAC (variable 4) method than DPPH (variable 3), and the antioxidant activity measured by ABTS and ORAC is more correlated with flavonoids than phenolic acids, since their structure has higher antioxidant potential reported. The distribution of BE apple extracts along PC1 and PC2 plot could be divided into three main groups, allowing to understand which variables contributed more to the distribution obtained. The first, which is located on the positive side of the PC1 and PC2, includes the MAE extract; the second, positioned on the positive side of PC1 and the negative side of PC2, comprises the CET extract; and the third, located on the negative side of PC1 and on the positive side PC2, includes UAE and CE. The CE and UAE extracts are distinguished from the others due to their low content in phenolic compounds as well as antioxidant activity. Due to the analysis of the variables, it was possible to verify that DPPH was correlated with the amount of cryptochlorogenic acid and quercetin-3-rutinoside present in the extracts, due to the nature of these compounds, as they have shown affinity to organic solvents reflecting better results in DPPH method than in ABTS\({}^{\circ}\) method. The MAE and CET exhibited a higher amount of phenolic compounds as well as greater antioxidant activity. In particular, MAE exhibited the highest amount of caffeoylquinic acids, procyanidins and quercetin-3-rutinoside as well as the greatest antioxidant activity in scavenging DPPH. Moreover, this extraction method is distinguished from the CET by its higher contents of phloridzin and phloretin and great antioxidant activity by ORAC and ABTS assays. These results suggest that these compounds could be the major contributors for the ORAC and ABTS values obtained. The use of CET to produce BE apple extracts showed to be a technique with good results, yet it is more time- and energy-consuming comparatively to MAE. Furthermore, since the MAE are on the positive side of both PCs and MAE application for 1.5 min allowed to obtain a polyphenol-rich extracts with higher antioxidant activity in ORAC. It is possible to conclude that MAE is more efficient than the CET method to produce the BE extracts. One of the most important \begin{table}
\begin{tabular}{c c} \hline \hline \multicolumn{2}{c}{**BE Apple Extracts**} \\ \hline
**Number** & **Variable Designation** \\ \hline
1 & Total Phenolic Content \\
2 & ABTS method \\
3 & DPPH method \\
4 & ORAC method \\
5 & Chlorogenic acid \\
6 & Cryptochlorogenic acid \\
7 & _p_-Coumaroylquinic acid \\
8 & _p_-Coumaric acid \\
9 & (+)-Catechin \\
10 & (\(-\))-epictatechin \\
11 & Epicatechin-3-gallate \\
12 & Procyanidin B2 \\
13 & Procyanidin C1 \\
14 & Quercetin-3-rutinoside \\
15 & Phloretin \\
16 & Phloridzin \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Description of the 16 variables considered in PCA for BE apple extracts.