## 3 Results and Discussion  
### Polyphenols and Carotenoids Content  
This part of the presented research focused on the bioactive compounds' profiles of seventeen barley and eight oat cultivars grown in the controlled field trial under the organic farming conditions. The results of the analyses of phenolic acids, flavonoids and carotenoids concentrations are presented in Tables 2-6.  
grains. As previously reported, in barley grain, they are mainly found in the outer layers, but also in endosperm, while, in the oat grain, in the outer layer of the kernel, in the bran fraction of the grain. Other bound phenolic acids previously found to occur in barley and oat grain are vanillic and \(p\)-hydroxybenzoic acid [31; 32; 33]. Our results partly correspond with the results of other authors. [PERSON] et al. (2018) [33] reported the influence of genetic factors on phenolics contents of two varieties of _Avena sativa_ L., six varieties of _Avena nuda_ L. and one variety of wild oat (_Avena fatua_ L.). In this research, gallic acid, protocatechuic acid, \(p\)-hydroxybenzoic acid and vanillic acid were the major phenolic acids found in all the samples, while in our research the most abundant were ferulic, \(p\)-coumaric and caffeic acid. Although the contents of some of the individual phenolic acids in the present study were different from those reported by other researchers [33], the sum of the concentrations of all the identified phenolic acids was similar. [PERSON] and co-authors [31], who investigated phenolics content in different barley varieties, detected seven phenolic acids (gallic, protocatechuic, vanillic, caffeic, \(p\)-coumaric, t-ferulic and sinapic). Their results are in line with ours in the main phenolic acids occurrence, because in both studies ferulic, \(p\)-coumaric and caffeic acids were the most abundant ones. Flavonoids are present in cereals in smaller quantities than phenolic acids [31], but they have an important role in the cereal plants, acting as ultraviolet B radiation absorbing compounds and thus protecting plants against excessive short-wavelength solar radiation [34]. At the same time, high dietary flavonoid intake has been shown to be inversely correlated with the risk of many non-communicable diseases associated with oxidative stress [35]. In the present study, flavonoids constituted around 26% of all polyphenols identified in barley and oat. The results on the flavonoids content (sum and individual compounds) in grains of all tested barley and oat cultivars are presented in Tables 4 and 5. We separated, identified and quantified six flavonoids in grains: quercetin-3-\(O\)-rutinoside, apigenin, kaempfer-3-\(O\)-glucose, quercetin, kaempfer and luteolin. Among the tested barley cultivars, the highest summary concentration of all the identified flavonoids was found in Ella, followed by Natasia, Soldo and Oberek cultivars (Table 4). Among the oat cultivars, Haker and Krezus were richest in flavonoids (Table 5). Quercetin-3-\(O\)-rutinoside was the most abundant flavonoid in barley. On average, it accounted for 37.8% of total flavonoids concentration. In oat, kaempfer and apigenin had a major share, accounting for 30.1% and 27.3% of the total flavonoid concentration, respectively. This is partly in line with the review on the antioxidants in oat [4], which indicated apigenin, luteolin and tricin as the main flavonoids in oat, but also confirmed the presence of some others glycosidic derivatives (i.e., 6-C and 8-C-glucose apigenin and 3-\(O\)-rutinosides of quercetin and kaempfer). According to [PERSON] and [PERSON] [36], the observed variation in the phenolic acids and flavonoids profiles reported in different studies is probably due to the different cultivars used, environmental conditions and degree of ripeness, as well as the extraction solvents and testing methods applied.