## 3 Results and Discussion
### Content of TPC Using the Folin-Ciocalteu Reagent Method
#### 3.1.4 Comparison of the Extracts Tested  
Based on the results obtained for extracts obtained with extraction by shaking them with a solvent (SSE) for 30 min, using ultrasound-assisted extraction (UAE) and accelerated extraction using a solvent (ASE), we prepared a chart showing the content of polyphenols in these extracts, expressed in mg GAE/1g of DW (Figure 3). Extracts prepared using the UAE method and the SSE method by shaking them with a solvent did not differ significantly in terms of polyphenol content (approx. 55 mg GAE/1 g of DW); however, they contained significantly more of these compounds compared to extracts obtained using the accelerated extraction method using a solvent (46.8 mg GAE/1 g of DW). There are no literature data on the extraction of polyphenols from apple leaves using the ASE method. The extraction most often used for this purpose is solvent extraction aided by ultrasound [6, 8, 18, 46]. [PERSON] et al. [35] showed that UAE is a better method of extracting polyphenols from orange peel than ASE. [PERSON] et al. [48] also confirmed that extraction using the UAE method is the most effective. The statistical analysis of all extracts, differing in the extraction method, type of solvent used, and apple leaf cultivar, showed that the solvent had the greatest impact on the polyphenol content in these extracts. The average content of total polyphenols in methanol extracts (80%) was 66.6 mg GAE/1 g of DW and was significantly the highest among all extracts. Ethanol extracts (40%) contained significantly more total polyphenols (53.3 mg GAE/1 g of DW) than water extracts (36.3 mg GAE/1 g of DW). The apple leaf cultivar did not significantly affect the content of total polyphenols in the extracts. As a result of a three-factor analysis of variance, as many as 13 homogeneous groups were distinguished, which indicates a large diversity of extracts in terms of polyphenol content. Water and methanol extracts from apple leaves of the Ligol cultivar obtained with the SSE method (81.9 mg GAE/1 g of DW) and using ASE (76.6 mg GAE/1 g of DW) had the significantly highest content of phenolic compounds. The latter did not differ significantly from water-alcoholic extracts from Ligol leaves obtained using UAE. The lowest polyphenol content was determined in the water extract from the apple leaves of the Gloster cultivar, obtained using the SSE method (29.2 mg GAE/1 g of DW). However, the  
Figure 2: Content of total polyphenols in apple leaf extracts obtained with accelerated solvent extraction. same homogeneous group also included the following extracts: water and water-ethanol extracts from the leaves of the Gloster cultivar obtained using ASE method, aqueous extracts from the leaves of the Gala cultivar obtained using the SSE method, and aqueous extracts from the leaves of the Gala and Gloster cultivars obtained using UAE method. The type of solvent used to extract polyphenols is one of the most important factors affecting the efficiency of this process. According to [PERSON] [42], in many cases, depending on the plant raw material used, the best extractant is a 70% or 40% solution of ethanol in water. [PERSON] et al. [32] and [PERSON] et al. [41] also confirmed that at least two-component mixtures are the best extractants due to the different polar properties of polyphenols. [PERSON] et al. [43] showed that extraction with methanol allows for a better extraction of polyphenols than extraction with ethanol. The content of total polyphenols in apple leaf extracts turned out to be much higher than in blackcurrant leaf extracts (22.2 mg GAE/1 g of DW). Apple leaf extracts had a similar polyphenol content compared to blueberry fruit (55.1 mg GAE/1 g of DW) and black tea leaves (depending on origin from 26.3 to 92.1 mg GAE/1 g of DW) [49; 50]. Identification and Determination of Polyphenol Content Using High-Performance Liquid Chromatography (HPLC-DAD)  
Identification and determination of the content of phenolic compounds was carried out using the HPLC method.