## 3 Results
### Influence of Different Drying Methods on the Composition of Chlorophylls and Carotenoids  
The content of chlorophyll \(a\) and \(b\), total chlorophylls and carotenoids, as well as the ratios of chlorophyll \(a/b\) and total chlorophylls to carotenoids in yellow ginkgo leaves dried using three different methods are presented in Table 1.  
According to the data presented in Table 1, the highest content of chlorophyll \(a\) and \(b\) and total chlorophyll was observed in the samples dried by oven drying, followed by freeze drying and air drying. However, the total carotenoid content showed no statistical differences between the three drying methods and all leaf samples showed values in the range of 159-174 \(\upmu\)g/g dw. The ratio of chlorophyll \(a\) to chlorophyll \(b\) was lower in the air-dried samples and comparable in the freeze-dried and oven-dried samples. Similarly, the chlorophyll/carotenoid content was also much lower in air-dried leaves. The low chlorophyll/carotenoid content indicates a higher carotenoid content, which is to be expected in yellow leaves as we used in this experiment. Influence of Different Drying Methods on the Content of the Total Polyphenols, Flavonoids, Phenolic Acids and Individual Biflavonoids  
The influence of the different drying methods on the content of total polyphenols, total flavonoids and total phenolic acids is shown in Figure 3.  
The total content of polyphenols and flavonoids did not differ significantly in the leaf samples dried by different methods. Non-significantly, the highest levels of total flavonoids were found in the freeze-dried samples (5.32 \(\pm\) 0.13 \(\upmu\)g CAE/mg dw), while the oven-dried samples had the highest levels of total polyphenols (49.92 \(\pm\) 1.81 \(\upmu\)g GAE/mg dw). \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Freeze Drying** & **Air Drying** & **Oven Drying** \\ \hline Chlorophyll \(a\) (\(\upmu\)g/g dw) & 64.40 \(\pm\) 2.03 \({}^{\text{b}}\) & 20.32 \(\pm\) 0.95 \({}^{\text{c}}\) & 86.27 \(\pm\) 3.12 \({}^{\text{a}}\) \\ Chlorophyll \(b\) (\(\upmu\)g/g dw) & 22.78 \(\pm\) 1.52 \({}^{\text{b}}\) & 15.15 \(\pm\) 0.93 \({}^{\text{c}}\) & 30.74 \(\pm\) 3.59 \({}^{\text{a}}\) \\ Total chlorophylls (\(\upmu\)g/g dw) & 87.18 \(\pm\) 2.81 \({}^{\text{b}}\) & 35.47 \(\pm\) 1.86 \({}^{\text{c}}\) & 117.01 \(\pm\) 6.54 \({}^{\text{a}}\) \\ Total carotenoids (\(\upmu\)g/g dw) & 174.78 \(\pm\) 8.04 \({}^{\text{a}}\) & 164.60 \(\pm\) 5.81 \({}^{\text{a}}\) & 159.8 \(\pm\) 6.03 \({}^{\text{a}}\) \\ Chlorophyll \(a\)/Chlorophyll \(b\) & 2.84 \(\pm\) 0.20 \({}^{\text{a}}\) & 1.34 \(\pm\) 0.03 \({}^{\text{b}}\) & 2.84 \(\pm\) 0.26 \({}^{\text{a}}\) \\ Chlorophylls/carotenoids & 0.50 \(\pm\) 0.01 \({}^{\text{b}}\) & 0.22 \(\pm\) 0.01 \({}^{\text{c}}\) & 0.73 \(\pm\) 0.02 \({}^{\text{a}}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The content of pigments in yellow ginkgo leaves affected by different drying methods. Values marked with different letters are significantly different at \(p\) ¡ 0.05. Figure 3: Total polyphenols (**a**), total flavonoids (**b**) and total phenolic acids (**c**) for the three types of drying used on yellow ginkgo leaves. Values marked with different letters are significantly different at \(p\) ¡ 0.05. Oven-dried leaves had the highest content of total phenolic acids (1.64 \(\pm\) 0.04 \(\upmu\)g CA/mg dw), and this value was significantly higher. The influence of different drying methods on the individual composition of biflavonoids in yellow ginkgo leaves is shown in Figure 4.  
The most abundant biflavonoids were isoginkgetin and bilobetin, the amount of which exceeded 1000 \(\upmu\)g/g dw in all leaf samples. They were followed by ginkgetin and sciadopitysin, the amounts of which were about 30% lower, in the range of 700-800 \(\upmu\)g/g dw. The least abundant was amentoflavone, which was just over 100 \(\upmu\)g/g dw, 10 times less than isoginkgetin and bilobetin.