## 4 Discussion  
Polyphenols contribute to a wide range of biological properties of herbal samples. They can be major active ingredients or a valuable addition, demonstrating a synergistic effect with other natural molecules or synthetic drugs [28]. Therefore, sources of bioactive polyphenols are still searched and evaluated. Moreover, the content and profile of polyphenols is an important phytochemical and chemotaxonomic information as well. The present study was designed to analyze the total polyphenol content and antioxidant activity of juniper extracts in order to reveal species of different origin, exhibiting highest activity, and to identify the phytochemicals (secondary metabolites) responsible for these properties. Antioxidant activity, particularly antiradical activity, is very important due to the deleterious role of free radicals in biological systems and food. Plants rich in secondary metabolites, including phenolic compounds, have antioxidant activity related to their redox properties. The DPPH screening is one of the most widely used tests for the evaluation of the antioxidant activity of the extracts [29]. Thus, the first step of the study was aimed at identifying juniper extracts with highest TPC content correlated with high antiradical potential measured as DPPH-radical scavenging ability. This screening enabled the designation of the most promising juniper extracts for further detailed studies of polyphenolic profile and biological assays. It was found that all samples contain large amount of polyphenols (45-263 mg GAE/g of dry extract (DE)). For several juniper leaf extracts, TPC values were found to be outstanding (>180 mg/g DE): _J. ashei_ [PERSON]. [PERSON] > _J. pinchotti_ [PERSON]. > _J. communis_ [PERSON] \(\geq\)_J. formosana_ Hayata. > _J. isbirica_ [PERSON]. It could be noticed that the leaf extracts demonstrated higher antioxidant properties than the corresponding galbuli extracts, as it was shown by analysis of the leaves and galbuli extracts of _J. chinensis_ L., _J. virginiana_ L., as well as cultivars _J. virginiana_ 'Glauca' and _J. virginiana_ 'Grey Owl'. TPC values were significantly higher than those reported for _Juniperus pheonica_ L. leaves (6.3 and 9.6 mg/g) by [PERSON] et al. [17]. On the other hand, the TPC values found for galbuli (\"berries\") were lower than those reported for _J. communis_ and _J. axycedrus_[29]. It can be noticed that the TPC values of juniper samples are strictly species and organ-dependent. Moreover, differences in phenolic content may be related to the different growing or/and climate conditions. All samples had radical scavenging action in the DPPH radical scavenging assay test (Table 1). Determined EC\({}_{50}\) values ranged from 49 to 352 mg DE/mL. The lowest values (indicating the highest activity) were found for _J. ashei_, _J. pinchotti_, and _J. formosana_ (49-86 mg DE/mL). _Juniperus_ samples (e.g., _J. communis_, _J. formosana_, and _J. sibrica_ ethanolic extracts) were previously reported to be effective radical scavengers with EC\({}_{50}\) 21.39-28.55 ug/mL [29; 30]. Interestingly, it was observed that juniper ethanol extracts are more effective than essential oils obtained from the corresponding plant materials [30]. After identification of the best antioxidant plants in the group of all assayed junipers, the LC-ESI-MS/MS-MRM technique was employed for the qualitative and quantitative determination of the secondary metabolites (phenolic acids, flavonoid aglycones, flavonoid glycosides), which is responsible for the highest activity of best antioxidant extracts. It was observed that phenolic acids constitute a relatively small part of all polyphenols, with protocatechuric acid as a dominant representative (up to 43.3 ng/mg DE). The majority of them belong to hydroxybenzoic acid derivatives (4-OH-benzoic, salicylic, protocatechuric, gallic). Only one hydroxycinamic acid derivative was found, i.e., _p_-coumaric acid. The highest amount of phenolic acids was found in _J. sibrica_ extract, whereas _J.