## 1 Introduction  
The genus _Salix_ L. consists of about 500 species distributed mainly in the northern hemisphere, out of which 65 grow in Europe and about 20 are indigenous to the Balkan Peninsula [1, 2]. Willow bark (_Salix_ spp., Salicaceae) is a traditional herbal remedy used to treat pain, fever and inflammation [3]. Contrary to bark, leaves of many _Salix_ species are mainly not studied and there is a general lack of data concerning their medicinal properties. While pharmacological effects of willow bark are mainly attributed to salicin as the major active constituent, newer studies suggest that these effects cannot be explained solely by the presence of salicin and its derivatives, but that other compounds such as flavonoids (flavan-3-ols) and simple phenols (phenolic acids) synergistically contribute to the therapeutic effects of willow bark [4, 5, 6, 7]. Certain _Salix_ species are known to exhibit strong antioxidant activity in many in vitro systems [8, 9]. The anti-inflammatory effect of some phenolic acids has been associated with their antioxidant activity [10]. Antioxidants can protect biomolecules (lipids, proteins and nucleic acids) against potentially harmful effects of free radicals. Oxidative stress, resulting from the imbalance between free radical production and antioxidant defenses, is thought to promote many diseases such as cancer, cardiovascular and neurodegenerative, including Alzheimer's disease (AD) [11]. One of the main causes of AD is low level of acetylcholine (ACh) in the synapses of human cerebral cortex, leading to loss of memory and impairment of multiple cerebral functions [12]. Synthetic inhibitors of acetylcholinesterase (AChE) are standard therapy of AD, preventing the hydrolysis of ACh, thus maintaining the neurotransmitter in acceptable concentrations and improving cognitive functions. However, numerous side effects limit their use and urge a search for safer and more effective therapeutic options of natural origin [13].  
Studies dealing with phytochemical characterization of various species from the genus _Salix_ have focused mainly on salicylic compounds found in bark [14]. Phenolic constituents in leaves, leaf buds, flower buds and twigs in several Finnish _Salix_ species were investigated, but the research also included mainly the analysis of salicin derivatives [15]. Simple phenols were analyzed to a certain extent in bark of ten species of the genus _Salix_[10]. However, there is no comparative analysis of simple phenolics and flavonoids in bark and leaves of different _Salix_ species, as well as of their antioxidant potential. In addition, there is no information available in literature about the chemical composition of _S. amplexiaulis_, _S. babylonica_ and _S. elegans_. Therefore, the primary aim of this research was to determine the chemical composition and antioxidant potential of bark and leaves of seven species indigenous to the Balkan Peninsula, namely _S. alba_, _S. amplexiaulis_, _S. babylonica_, _S. elegans_, _S. fragilis_, _S. purpurea_ and _S. triandra_. The secondary goal of this paper was to elucidate the interaction and binding affinity between selected compounds of willow extracts and AChE using molecular docking. It would be of significant interest to exploit these widely distributed and easily accessible plant crops as sources of valuable phytochemicals in the pharmaceutical industry.