## 3 Results and Discussion
### Relations Between Cultivars and Parameters Tested  
To further explore the differences and similarities between the tested barley and oat cultivars produced in the organic farming conditions in terms of the contents of polyphenolic and carotenoid compounds and mycotoxins contamination, a principal component analysis (PCA) was performed (Figures 1-4). The result of the PCA for the bioactive compounds of barley and oat cultivars showed a high overall variation (54.34% and 53.28%, respectively) explained by PC1 and PC2 (Figures 1 and 2). Three groups of barley cultivars located in different quarters of the PCA plot were associated with different groups of compounds (Figure 1). Among all cultivars in the experiment, Rubaszek, SU Lolek and Podarek were characterized by a higher content of ferulic acid (main phenolic acid) and phenolics in general. In comparison, cultivars such as Soldo and Ella were associated with a higher content of flavonoids when compared to others. This confirms significant differences in the bioactive compound profiles/patterns between groups of barley cultivars tested. Oat cultivars are more scattered across the PCA plot, which suggests the absence of strong similarities between cultivars tested for bioactive compounds (Figure 2). For example, cultivars Arden and Navigator were similar in the content of kaempfer and sinapic acid, while differed in the content of ferulic acid, kaempfer-3-\(O\)-glucose, gallic acid or quercetin-3-\(O\)-glucose. The results of the PCA for the mycotoxin contamination showed that the first two components describe 85.19% (in barley cultivars) and 97.74% (in oat cultivars) of the initial variability (Figures 3 and 4). A strong divergence was observed between the barley cultivars (Figure 3). In comparison with all other cultivars, Soldo was strongly associated with the contamination of DON, T-2, HT-2 and ZEA mycotoxins. In addition, strong associations were found for Natasia and SU Lolek cultivars and the content of mycotoxins FB1, FB2 and OTA. All other cultivars were associated with mycotoxin contamination in a much lesser extent. Oat cultivars Harnas and Haker were both associated with OTA and FB2, and cultivar Arden with 15-AcDON mycotoxins contamination (Figure 4). Figure 1: PCA biplot showing the relationships between the chemical composition of grains of the studied barley cultivars. Lutein (Lut), \(\beta\)-carotene (B-C), gallic acid (GA), ferulic acid (FA), caffe acid (CA), t-cinnamic acid (t-CA), sinapic acid (S), \(p\)-coumaric acid (p-C), sum of phenolic acids (TPA), quercetin-3-\(O\)-glucose (Q-3-O-R), kaempfer-3-\(O\)-glucose (K-3-O-G), luteolin (L), quercetin (Q), apigenin (Ap), kaempfer (K), total flavonoids (TF), total polyphenols (TP). The Pearson's correlation analysis showed some significant relationships between the content of the analyzed groups of bioactive compounds and the individual antioxidants in oat and barley grain samples (Figures 5 and 6). In barley, the strongest positive correlations were identified between the contents of the sum of polyphenols and the sum of phenolic acids (r = 0.97, \(p<0.001\)) and between  
Figure 3: PCA biplot showing the relationships between the mycotoxins contamination of grains of the studied barley cultivars. Ochratoxin A (OTA), fumonisin B1 (FB1), fumonisin B2 (FB2), zearalenone (ZEN), T-2 toxin (T-2), HT-2 toxin (HT-2), deoxynivalenol (DON), 15-acetylodeoxynivalenol (15-DON). Figure 2: PCA biplot showing the relationships between the chemical composition of grains of the studied oat cultivars. Lutein (Lut), \(\beta\)-carotene (B-C), gallic acid (GA), ferulic acid (FA), caffeic acid (CA), t-cinnamic acid (t-CA), sinapic acid (S), \(p\)-coumaric acid (p-C), sum of phenolic acids (TPA), quercetin-3-O-glucose (Q-3-O-R), kaempfer-3-O-glucose (K-3-O-G), luteolin (L), quercetin (Q), apigenin (Ap), kaempfer (K), total flavonoids (TF), total polyphenols (TP).