# Sea Buckthorn Leaves as a Potential Source of Antioxidant Substances
## 3 Results and Discussion
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Factor**} & **Total Polyphenols** & **TEAC \({}^{4}\) ABTS*+** & **TEAC DPPH*+** & **PCL** \\  & **(mg GAE 2/1 g DM 3)** & **(uM TRX 5/1 g DM)** & **(uM TRX/1 g DM)** & **μM TRX/1 g DM** \\ \hline \multicolumn{5}{c}{Year} \\ \(p\)\({}^{6}\) & =0.029 & =0.071 & \textless{}0.000 & =0.905 \\
2014 & 186.64 a \({}^{7}\) & 491.86 a \({}^{8}\) & 340.57 b & 348.49 a \\
2015 & 197.43 ab & 493.36 a \({}^{8}\) & 350.04 b & 313.23 a \\
2016 & 330.16 b & 494.61 a & 299.53 a & 310.98 a \\ \hline \multicolumn{5}{c}{Cultivar} \\ \(p\) & =0.239 & =0.036 & =0.095 & =0.148 \\ Ascola & 307.02 a & 490.47 a \({}^{8}\) & 323.49 a & 290.76 a \\ Habego & 216.26 a & 492.82 ab & 329.53 a & 245.20 a \\ Hergo & 195.80 a & 493.32 b & 332.94 a & 254.41 a \\ Leikora & 233.25 a & 492.50 ab & 334.23 a & 506.57 a \\ \hline \hline \end{tabular} \({}^{1}\) SBT—sea buckthorn; \({}^{2}\) GAE—gallic acid equivalent; \({}^{3}\) DM—dry matter; \({}^{4}\) TEAC—Trolox equivalent antioxidant capacity; \({}^{5}\) TRX—Trolox; \({}^{6}\)—probability of null hypothesis rejection (H0; m\({}_{1}\) = m\({}_{2}\)... = m\({}_{h}\)); \({}^{7}\) means with at least one same letter (a, b) do not differ statistically at \(p\) = 0.05 (for all columns, separately).  
\end{table} 
Table 1: The total polyphenol content and antioxidant activity of SBT \({}^{1}\) leaves. Figure 2: The first two principal component axes for polyphenol content and antioxidant activity in SBT leaves for the variables (**A**) and for the scores (**B**), (ABTS—2,2\({}^{\prime}\)-azino-bis(3-ethylbenzothazoline-6-sulfonic acid; DPPH—1,1-diphenyl-2-picrylhydrazyl; PCL—photochemiluminescence assay; TP—Total Polyphenol; A—cv. Ascola; HA—cv. Habego; HE—cv. Hergo; L—cv. Leikora). The largest group of plant polyphenols (TPs) are flavonoids (TFs). Within this group, several subclasses have been distinguished, differing in structure and resulting antioxidant activity. The phenolic compounds quantified are generally considered to be the major determinants for the antioxidant capacity of plants. The total flavonoid (TF) content in the leaves of sea buckthorn are shown in Table 4. The average TF content of SBT leaves was high at 281.76 mg QEE/1 g DM. However, there was no significant effect of growing season or cultivar on the TF content of sea buckthorn leaves. The total flavonoid content of 36.58 mg of mg QEE per 1 g of extract was found in the leaves of SBT grown in Romania by [PERSON] et al. [11]. This value is relatively lower than our results, but our results are expressed on 1 g of DM, and this is not clearly stated in the referenced study. [PERSON] et al. [59] found TF content in SBT leaves ranging from 24.57 to 34.83 mg rutin/g DM. The content of these compounds in sea buckthorn leaves was not affected by the factors studied, but the presence of rutoside and quercetin was found to be significant. The content of these compounds in the leaves of the tested cultivars was the same, but the raw material from different growing seasons contained statistically different contents. The average flavonol content was 80.19 mg QEE/1 g DM (Table 4). The flavonoid content in the leaves and fruit of sea buckthorn has been reported to range from 310 to 2100 mg/100 g of dried leaf and 120 to 1000 mg/100 g of fresh fruit, respectively [60; 61; 62]. Due to the different methods of determination and the different standards used, it is impossible to compare the results obtained. However, it has been widely confirmed that SBTs are rich in phenolic compounds. The content of individual flavonoids in the studied SBT leaves was statistically differentiated by the experimental factors analysed. The content of proanthocyanidin, anthocyanin, and total tannins was significantly influenced by the origin of the raw material (growing season). PACs are a group of condensed tannins consisting of catechin and epicatechin monomers that differ from the hydrolysate tannin structure of ellagitannins.