## 3 Results and Discussion
### Antioxidant Activity of S. repens  
At the final stage, it was decided to evaluate the antioxidant activity of _S. repens_ SPE fractions from leaves and roots of _S. repens_ have been evaluated for antioxidant activity against 2,2-diphenyl-1-picrylhydrazyl radical (DPPH-) (Table 3). Scavenging activity against DPPH radical of _S. repens_ SPE fractions were low to medium. Both SPE-1 fractions as well as the SPE-2 fraction from the roots were characterized by low activity (<1 mg trolox/g). The antiradical activity of the SPE-2 fraction from leaves of S. repens against DPPH was in the range of 33.75-78.20 mg trolox/g. The highest antiradical activity (60.92 and 78.20 mg trolox/g) was noted for fractions obtained after the treatment with 4-chlorophenylacetic acid (10 and 100 mg/L, respectively). Previously, for extracts from six species of _Silene_ growing in Turkey, antiradical activity against DPPH- was established in the range of 43-131 mg trolox/g [53]. For _S. vulgaris_ extract, the half maximal inhibitory concentration (IC\({}_{50}\)) was 3.31 mg/mL [54], while for _S. lafifolia_ extracts IC\({}_{50}\) was 1.26-1.57 mg/mL in relation to the DPPH radical [55]. Thus, _S. repens_ had antioxidant properties typical for other _Silene_ species. To determine compounds responsible for the antioxidant activity, the SPE-2 fraction from leaves of _S. repens_ was subjected to HPLC-PDA activity-based profiling (Figure 5). \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Group**} & \multirow{2}{*}{**Concentration,**} & \multicolumn{6}{c}{**Content of Glycos/filavones, mg/g \(\pm\) S.D.4,b**} \\ \cline{3-10}  & & **mg/L** & **13** & **14** & **15** & **16** & **17** & **18** & **\(\Sigma_{\text{13-18}}\)** \\ \hline Control 1 (water, & & & & & & & & & \\ spraying) & - & 0.60 \(\pm\) 0.01 & 0.73 \(\pm\) 0.02 & 0.02 \(\pm\) 0.00 & 0.08 \(\pm\) 0.00 & 0.15 \(\pm\) 0.00 & 0.07 \(\pm\) 0.00 & 1.65 \\ \hline Control 2 (watering) & - & 0.63 \(\pm\) 0.01 & 0.74 \(\pm\) 0.02 & 0.02 \(\pm\) 0.00 & 0.06 \(\pm\) 0.00 & 0.17 \(\pm\) 0.00 & 0.08 \(\pm\) 0.00 & 1.70 \\ \hline \multirow{2}{*}{Epibrassinolide} & 1 & 0.58 \(\pm\) 0.01 & 0.79 \(\pm\) 0.02 & tr. & 0.03 \(\pm\) 0.00 & 0.10 \(\pm\) 0.00 & 0.04 \(\pm\) 0.00 & 1.54 \\  & 10 & 0.77 \(\pm\) 0.01 1 & 1.14 \(\pm\) 0.02 1  & tr. & 0.02 \(\pm\) 0.00 & 0.10 \(\pm\) 0.00 & 0.08 \(\pm\) 0.00 & 1.70 \\  & 10 & 0.56 \(\pm\) 0.01 & 1.12 \(\pm\) 0.02 1  & tr. & 0.03 \(\pm\) 0.00 & 0.10 \(\pm\) 0.00 & 0.06 \(\pm\) 0.00 & 1.74 \\  & 10 & 0.70 \(\pm\) 0.02 1  & 0.02 \(\pm\) 0.00 & 0.12 \(\pm\) 0.00 1  & 0.07 \(\pm\) 0.00 & 0.08 \(\pm\) 0.00 & 0.08 \(\pm\) 0.00 & 0.08 \(\pm\) 0.00 & 1.70 \\
4-Chlorophenylacetic acid & 10 & 0.66 \(\pm\) 0.01 & 1.16 \(\pm\) 0.02 1  & 0.02 \(\pm\) 0.00 & 0.10 \(\pm\) 0.00 & 0.06 \(\pm\) 0.00 & 1.74 \\  & 10 & 0.70 \(\pm\) 0.02 1  & 0.02 \(\pm\) 0.00 & 0.12 \(\pm\) 0.00 1  & 0.07 \(\pm\) 0.00 & 0.08 \(\pm\) 0.00 & 0.17 \(\pm\) 0.00 & 0.05 \(\pm\) 0.00 & 1.56 \\  & 10 & 0.32 \(\pm\) 0.01 1  & 0.08 \(\pm\) 0.00 & 0.57 \(\pm\) 0.00 & 0.06 \(\pm\) 0.00 & 1.61 \\ \hline \multirow{2}{*}{Arachidonic acid} & 1 & 0.53 \(\pm\) 0.01 & 0.63 \(\pm\) 0.01 & 0.03 \(\pm\) 0.00 & 0.07 \(\pm\) 0.00 & 0. For the procedure of small-scale, semi-preparative microfraction by HPLC-PDA of _S. repens_, the SPE-2 leaves fraction was used. This method is characterized by post-column collecting of microfractions, subsequent drying, and analysis of obtained fractions to assess biological activity [56]. As a result of microfractionation of _S. repens_ SPE-2, 48 microfractions of 15 s each were obtained, then DPPH solution was added to evaluate antioxidant activity of the fractions obtained. The maximum inhibition of DPPH radical was observed in the time window of 5.45 to 7.45 min, corresponding to eight fractions. The  
Figure 5: DPPH: free radical inhibiting activity of HPLC fraction of _S. repens_ leaves SPE-2 fraction (Control 1 sample). The grey bars showed the antioxidant activity (as percentage) in probe after reaction with DPPH solution. The HPLC-PDA profile of _S.