## 3 Results and Discussion
### Chemical Composition of Bark and Leaves Extracts of Various Species from the Genus Salix
triandra_ \\  & & & & **(mg/g of leaf)** & & & & \\ GA & n.d. & n.d. & 0.20 \(\pm\) 0.01 a & n.d. & n.d. & n.d. & n.d. \\ CHLA & 2.26 \(\pm\) 0.04 d & 0.74 \(\pm\) 0.35 a & 1.62 \(\pm\) 0.02 c & 2.22 \(\pm\) 0.21 d & 5.82 \(\pm\) 0.09 e & 1.04 \(\pm\) 0.27 b & 7.53 \(\pm\) 0.07 f \\ PHB & 0.36 \(\pm\) 0.11 ab & 0.27\(\pm\)0.13 a & 0.46\(\pm\)0.15 b & 0.39\(\pm\)0.05 b & n.d. & n.d. & n.d. \\ VA & n.d. & n.d. & n.d. & n.d. & 0.35\(\pm\)0.35 & n.d. & n.d. \\ SA & 0.11 \(\pm\) 0.01 a & n.d. & 0.20 \(\pm\) 0.01 b & 0.19\(\pm\)0.00 b & 0.16\(\pm\)0.05 b & n.d. & 0.18 \(\pm\) 0.08 b \\ CA & n.d. & n.d. & n.d. & n.d. & 0.46 \(\pm\) 0.04 & n.d. & n.d. \\ EPC & 0.96 \(\pm\) 0.06 b & 0.71 \(\pm\) 0. In the analyzed extracts, a total of 13 compounds were identified and quantified: Gallic, chlorogenic, p-hydroxybenzoic, vanillic, syringic, caffe, p-coumaric and trans-cinnamic acids, flavonoids epicatechin, rutin, quercetin and naringenin, and the salicylic glycoside salicin. It is notable that chlorogenic, p-coumaric and trans-cinnamic acids and the analyzed flavonoids were present in bark and leaves extracts of all willlow species, but their amounts vary between samples. In bark of five out of seven willow species, the most abundant components were salicin, rutin, epicatechin and chlorogenic acid. Bark extracts of _S. ampleicaulis_ and _S. purpurea_ showed a slightly different pattern. Beside salicin and rutin, dominant compounds in bark of _S. ampleicaulis_ were p-coumaric and chlorogenic acid, whereas in bark of _S. purpurea_ those were epicatechin and p-coumaric acid. A distribution of components similar to that in bark was observed in leaves extracts of the respective species as well. Presence of variability in concentrations of salicin, rutin, chlorogenic acid and epicatechin between leaves samples of different species, as well as between bark and leaves within the same willow species is particularly evident. It is notable that the highest concentration of salicin was found in leaves of _S. purpurea_, but it was not detected in leaves of _S. alba_. Among all the extracts, the highest amount of salicin was found in leaves of _S. purpurea_, which is about twice as high as the amount in bark of the same species. Bark of _S. purpurea_ is considered as one of the richest sources of salicin among the willows [16]. Knowing that leaves of this species contain even higher concentrations of salicin opens up new possibilities for the exploitation of leaves as valuable and easily accessible sources of salicin. Among the bark extracts, the highest level of salicin was observed in _S. ampleicaulis_ and _S. purpurea_. This could be explained by the fact that these two species belong to the same subsection Purpurea (subgenus Vetrix, section Helix) [30,31] and therefore are likely to contain similar amounts of salicin. Compared to the results of a study from Turkey where the amount of salicin was determined in methanolic bark and leaves extracts of several _Salix_ species [20], our results indicate higher concentrations of salicin in bark of _S. fragilis_ and leaf of _S. triandra_, whereas lower in bark and leaves of _S. alba_, _S. ampleicaulis_ and _S. babylonica_. The amount of salicin in bark of _S. ampleicaulis_ from our study is found to be higher than that in methanolic extract of whole stem tissue of the same species [32]. On the other hand, salicin levels in ethanolic bark and leaves extracts of the other six analyzed willow species are lower than those found in methanolic extracts of whole stem tissue of the respective species [32]. These variations could be ascribed to different part of the plant, polarity of solvent used for extraction, as well as environmental and growth conditions of the species. Moreover, secondary metabolite content in willows varies with season and time of the day, but also gender and age of the plant [33]. Presence of rutin in the analyzed extracts is in accordance with the results obtained for _S.