## 3 Results and Discussion
### Content of TPC Using the Folin-Ciocalteu Reagent Method
#### 3.1.4 Comparison of the Extracts Tested
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{
\begin{tabular}{c} **Apple** \\ **Cultivar** \\ \end{tabular} } & \multicolumn{4}{c}{**Content of Phenolic Compounds in Extracts (mg/1 g of DW)**} \\ \cline{2-6}  & **Epicatechin** & **Rutin** & **Hyperoside** & **Isoquercitrin** & **Phloridinzin** & **Phloretin** \\ \hline Ligol & 0.373 \(\pm\) 0.244 \({}^{\text{a}}\) & 0.077 \(\pm\) 0.004 \({}^{\text{b}}\) & 0.263 \(\pm\) 0.044 \({}^{\text{b}}\) & 2.080 \(\pm\) 0.790 \({}^{\text{a}}\) & 54.941 \(\pm\) 41.991 \({}^{\text{a}}\) & 1.732 \(\pm\) 1.401 \({}^{\text{a}}\) \\ Gala & 0.358 \(\pm\) 0.210 \({}^{\text{b}}\) & 0.078 \(\pm\) 0.012 \({}^{\text{a}}\) & 0.266 \(\pm\) 0.052 \({}^{\text{a}}\) & 2.070 \(\pm\) 0.981 \({}^{\text{b}}\) & 41.313 \(\pm\) 35.477 \({}^{\text{b}}\) & 0.622 \(\pm\) 0.581 \({}^{\text{c}}\) \\ Gloster & 0.249 \(\pm\) 0.158 \({}^{\text{c}}\) & 0.076 \(\pm\) 0.005 \({}^{\text{c}}\) & 0.256 \(\pm\) 0.044 \({}^{\text{c}}\) & 1.960 \(\pm\) 0.930 \({}^{\text{c}}\) & 34.156 \(\pm\) 29.794 \({}^{\text{c}}\) & 1.008 \(\pm\) 0.852 \({}^{\text{b}}\) \\ \hline \hline \end{tabular}  
Mean values \(\pm\) SD. Letters (a–c) indicate significant differences in the content of phenolic compounds between different cultivars of apple leaves (\(p<0.05\)). Abbreviations: DW: dry weight.  
\end{table} 
Table 3: Content of phenolic compounds in extracts obtained from different cultivars of apple leaves. also noted significant differences in the polyphenol composition in extracts obtained from different cultivars of apple leaves [1; 3; 5; 6; 7; 8; 10; 12; 46]. Water-methanol extracts from apple leaves significantly contained the highest number of phenolic compounds identified with HPLC. Using this solvent, 1.8 times more epicatechin was extracted than using a mixture of water and ethanol and almost 4 times more than using water alone. The water-methanol extracts contained almost 2.3 times more phloridzin and 1.8 times more phloretin than the water-ethanol extracts. The difference resulted not only from the type of solvent used but also its concentration (methanol--80%, ethanol--40%). According to [PERSON] et al. [43], methanol allows for more efficient extraction than ethanol. However, research by [PERSON] et al. [41] confirms that the content of extracted phenolic compounds increases with the increase in the concentration of the alcohol solvent. The least amount of phenolic compounds was significantly determined in water extracts. In several water extracts, phloridzin and phloretin were not identified at all, and in the remaining ones, minimal amounts of these substances were determined compared to water and alcohol extracts (Tables 5-7). It can be concluded that epicatechin, isoquercitrin, phloridzin, and phloretin are much less soluble in water than in more polar solvents, such as ethanol and methanol. Therefore, to extract phenolic compounds from apple leaves, it is more appropriate to use mixtures of water and alcohol, preferably methanol. For each of the phenolic compounds identified on the basis of the pattern, a three-way analysis of variance was performed. Significantly, the most epicatechin was extracted from Ligol leaves using the SSE method using a water-methanol mixture (0.698 mg/1 g of DW). The water-ethanol extract from the leaves of the Gala cultivar obtained using ASE had a very similar content of epicatechin (0.692 mg/1 g of DW). Water-methanol extracts from the leaves of the Gala cultivar obtained using ASE significantly contained the highest amounts of all quercetin glycosides, i.e., rutin (0.105 mg/1 g of DW), hyperoside (0.340 mg/1 g of DW), and isoquercitrin (3.006 mg/1 g of DW). The highest content of phloridzin and phloretin was found in water-methanol extracts from the leaves of the Ligol cultivar, with the extract obtained using UAE having the significantly highest amount of phloridzin (105.00 mg/1 g of DW) and the extract obtained using ASE having the significantly highest amount of phloretin (3.371 mg/1 g of DW).