## 3 Results and Discussion
### Antioxidant Activity  
Natural products with antioxidant properties have become a hot topic nowadays as they represent safe alternatives to potentially toxic and carcinogenic synthetic antioxidants (such as butylated hydroxytoluene and butylated hydroxyanisole), which are widely used in food, pharmaceutical and cosmetic industry. The ability of bark and leaves extracts of various _Salix_ species to scavenge DPPH\({}^{\bullet}\) and \({}^{\bullet}\)OH was assessed. DPPH\({}^{\bullet}\) is a stable, nitrogen-containing free radical, violet/purple colored in ethanol solution, which fades to shades of yellow color in the presence of antioxidants. DPPH assay is one of the most widely used methods for screening antioxidant activities of plant extracts. It allows testing of lipophilic as well as hydrophilic compounds unlike other methods that are restricted in the nature of antioxidants [36]. \({}^{\bullet}\)OH is known as the most potent oxidant and one of the most reactive natural free radicals. It is directly involved in the irreversible damage caused by oxidative stress, which is one of the fundamental mechanisms underlying many human diseases such as malignant, cardiovascular and neurodegenerative [36; 37]. Concentrations of extracts that inhibited 50% (IC\({}_{50}\)) of DPPH\({}^{\bullet}\) ranged from 1.83-7.79 ug/mL in bark and 1.95-8.07 ug/mL in leaves extracts of different species of the genus _Salix_ (Table 4). Significant difference between the radical scavenging potential of bark and leaves extracts within the same species, as well as of different species, was found. The highest radical scavenging activity \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Species**} & \multicolumn{2}{c}{**DPPH\({}^{\bullet}\)1**} & \multicolumn{2}{c}{\({}^{\bullet}\)**OH 1**} \\ \cline{2-5}  & **Bark** & **Leaf** & **Bark** & **Leaf** \\  & & & **IC50 (\(\mu\)g/mL)** & \\ \hline _S. alba_ & 1.83 \(\pm\) 0.09 a  & 2.43 \(\pm\) 0.11 bc  & 34.76 \(\pm\) 0.24 s  & 42.18 \(\pm\) 0.32 l  \\ _S.uplexicaulis_ & 2.12 \(\pm\) 0.12 ab  & 7.05 \(\pm\) 0.15 s  & 51.69 \(\pm\) 0.31 l  \\ _S. babylonica_ & 2.59 \(\pm\) 0.16 c  & 4.43 \(\pm\) 0.17 de  & 40.44 \(\pm\) 0.56 h  & 44.61 \(\pm\) 0.39 c  \\ _S. elegans_ & 2.34 \(\pm\) 0.28 bc  & 5.51 \(\pm\) 0.19 f  & 29.71 \(\pm\) 0.29 e  & 51.96 \(\pm\) 0.14 l  \\ _S. fragilis_ & 4.11 \(\pm\) 0.13 d  & 8.07 \(\pm\) 0.43 h  & 22.20 \(\pm\) 0.36 a  & 25.15 \(\pm\) 0.46 b  \\ _S. purpurea_ & 4.73 \(\pm\) 0.26 e  & 7.34 \(\pm\) 0.16 g [FONOTE:s]Footnote s: footnotemark: [ENDFOOTNOTE] & 26.31 \(\pm\) 0.63 c  & 63.51 \(\pm\) 0.17 k  \\ _S. triandra_ & 7.79 \(\pm\) 0.21 h  & 1.95 \(\pm\) 0.08 a  & 28.01 \(\pm\) 0.29 d  & 36.10 \(\pm\) 0.18 h  \\ \hline \hline \end{tabular}
\end{table} 
Table 4: DPPH and OH radical scavenging activity of bark and leaves extracts of species from the genus _Salix_. against DPPH\({}^{\bullet}\) was observed in bark of _S. alba_, and the lowest in bark of _S. triandra_. Contrary to bark, leaves extract of _S. triandra_ exhibited the strongest DPPH\({}^{\bullet}\) quenching ability among the seven analyzed extracts. This could be explained by the fact that leaves extract of _S. triandra_ contains significantly higher amounts of total phenolics and flavonoids compared to bark of this species. The ability of ethanolic bark and leaves extracts of all seven analyzed species to scavenge DPPH\({}^{\bullet}\) was significantly stronger than the one of methanolic bark extract of _S. alba_ (15.5 \(\upmu\)g/mL) [28] indicating higher selectivity of ethanol for the extraction of antioxidant compounds. The analyzed bark and leaves extracts of willows also showed notable potential to inhibit \({}^{\bullet}\)OH generated in Fenton reaction. IC\({}_{50}\) values ranged from 22.20-51.63 \(\upmu\)g/mL and 25.15-63.51 \(\upmu\)g/mL for bark and leaves, respectively (Table 4). Generally, bark extracts had stronger \({}^{\bullet}\)OH scavenging potential than leaves, except for _S. amplexicaulis_, which showed the opposite.