## 3 Results and Discussion
### Effect of Extraction Conditions on Sea Buckthorn Leaves  
Sea buckthorn berries and leaves have been used as medicine and health food for thousands of years due to their bioactive compounds with strong antioxidant properties and significant therapeutic benefits. Therefore, it is important to develop an efficient and \begin{table}
\begin{tabular}{l c} \hline \hline \multicolumn{1}{c}{**Parameters**} \\ \hline Moisture content, \% & 5.37 \(\pm\) 0.23 \\ \hline Crude protein content, \% & 15.4 \(\pm\) 0.57 \\ \hline Fat content, \%, & 7.30 \(\pm\) 0.36 \\ of which: & 2.49 \(\pm\) 0.11 \\ saturated fatty acids, \% & 0.37 \(\pm\) 0.04 \\ polyunsaturated fatty acids, \% & 4.45 \(\pm\) 0.07 \\ omega-3 fatty acids, \% & 3.37 \(\pm\) 0.03 \\ omega-6 fatty acids, \% & 1.08 \(\pm\) 0.09 \\ omega-9 fatty acids, \% & 0.30 \(\pm\) 0.02 \\ \hline Carbohydrates, \% & 27.85 \(\pm\) 1.51 \\ Total sugar content, \% & 2.94 \(\pm\) 0.09 \\ of which: & \\ fructose, \% & 0.34 \(\pm\) 0.11 \\ glucose, \% & 1.28 \(\pm\) 0.09 \\ sucrose, \% & 1.34 \(\pm\) 0.07 \\ \hline Dietary fiber content, \% & 38.73 \(\pm\) 1.05 \\ of which: & \\ soluble & 3.51 \(\pm\) 0.16 \\ insoluble & 35.22 \(\pm\) 0.98 \\ \hline Mineral content, \% & 5.35 \(\pm\) 0.16 \\ of which: & \\ Potassium (K), mg/100 g & 66.29 \(\pm\) 2.91 \\ Magnesium (Mg), mg/100 g & 59.04 \(\pm\) 2.78 \\ Calcium (Ca), mg/100 g & 353.05 \(\pm\) 5.45 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Nutritional, compositional, quantitative, and qualitative indicators of raw materials for sea buckthorn leaves. environmentally friendly extraction method for these compounds [41; 42]. Currently, there is a scarcity of scientific studies employing PCSL extraction of sea buckthorn leaves using water as a solvent. Although ultrasonic extraction is commonly used, there are few studies where water is used as a solvent [43; 44]. More often, ethanol or methanol is used, which are not environmentally friendly [41; 43]. Furthermore, additional procedures are required to remove these solvents before using the extracts in the food industry. In this study, six different extracts of sea buckthorn leaves collected post-berry harvest were prepared using water as the extraction solvent. The extracts were obtained through PCSL extraction with varying numbers of extraction cycles and durations (see Table 2). The effects of these extraction conditions on the yield and composition of biologically active compounds, such as phenolic compounds and proanthocyanidins, were assessed. Extraction conditions notably influenced the concentration of bioactive compounds in the sea buckthorn leaf extracts. The extraction was performed in 20 and 60 cycles, with each cycle lasting from 2 to 10 min. PCSL extraction of sea buckthorn leaves under these conditions resulted in extracts with proanthocyanidin content ranging from 2.47 to 5.51 g\({}_{\text{CE}}\)/L and TPC ranging from 8.39 to 12.42 g\({}_{\text{GAE}}\)/L. The highest amount of biologically active compounds was observed in extracts obtained using 60 cycles, each lasting 10 min. However, compared to scientific publications, prolonged aqueous extraction is not environmentally friendly, similar to ultrasonic extraction methods that use ethanol and have a shorter extraction time of only 2 h. In such extracts, [PERSON] et al. [41] identified proanthocyanidins ranging from 7.86 to 14.57 g\({}_{\text{CE}}\)/L, depending on the sea buckthorn variety and harvest year. [PERSON] et al. [2], using ethanol as a solvent in microwave-assisted extraction and accelerated solvent extraction, found about 6-11 g\({}_{\text{GAE}}\)/100 g dry extract of TPC in extracts dependent on extraction conditions. The higher concentrations of biologically active compounds are described in these studies; however, the solvents used are not environmentally sustainable. Aqueous extracts may offer greater potential for application in food product development, such as in kombucha production. It also avoids removing the solvent before further use in the food industry.