## 3 Results and Discussion
### Polyphenols and Carotenoids Content
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \multirow{2}{*}{**N-Dose/Variety**} & \multirow{2}{*}{**Gallic Acid**} & \multirow{2}{*}{**Ferulic Acid**} & \multirow{2}{*}{**Caffeic Acid**} & \multirow{2}{*}{**\(t\)-Cinamic Acid**} & \multirow{2}{*}{**Sinapic Acid**} & \multirow{2}{*}{**\(p\)-Coumaric Acid**} & \multirow{2}{*}{**Sum of Acid**} \\  & & & & & & & Acid \\ \hline
60 kg N/ha & 2.52 \(\pm\) 0.33 A & 65.87 \(\pm\) 8.30 A & 0.96 \(\pm\) 0.52 AB & 0.95 \(\pm\) 0.58 AB & 1.42 \(\pm\) 0.03 A & 11.00 \(\pm\) 1.88 A & 82.69 \(\pm\) 9.68 A \\
90 kg N/ha & 3.01 \(\pm\) 0.21 B & 62.72 \(\pm\) 7.70 A & 1.09 \(\pm\) 0.65 B & 0.85 \(\pm\) 0.20 A & 1.41 \(\pm\) 0.03 A & 10.91 \(\pm\) 1.90 A & 79.99 \(\pm\) 8.83 A \\
120 kg N/ha & 3.28 \(\pm\) 0.60 C & 60.77 \(\pm\) 13.52 A & 0.64 \(\pm\) 0.40 A & 1.00 \(\pm\) 0.11 B & 1.44 \(\pm\) 0.02 B & 12.70 \(\pm\) 0.74 B & 79.82 \(\pm\) 13.70 A \\
150 kg N/ha & 3.52 \(\pm\) 0.37 D & 61.86 \(\pm\) 9.67 A & 0.73 \(\pm\) 0.46 A & 1.00 \(\pm\) 0.04 B & 1.44 \(\pm\) 0.02 B & 10.96 \(\pm\) 3.47 A & 79.51 \(\pm\) 10.31 A \\ \hline Zoom & 3.03 \(\pm\) 0.37 b & 68.59 \(\pm\) 8.39 a & 0.63 \(\pm\) 0.32 a & 0.99 \(\pm\) 0.10 b & 1.45 \(\pm\) 0.02 b & 9.94 \(\pm\) 3.13 a & 84.63 \(\pm\) 0.95 a \\ Hobbit & 3.42 \(\pm\) 0.79 c & 61.98 \(\pm\) 12.89 a & 0.67 \(\pm\) 0.46 b & 0.99 \(\pm\) 0.06 b & 1.44 \(\pm\) 0.02 b & 10.87 \(\pm\) 1.72 a & 79.35 \(\pm\) 1.39 a \\ Galation & 3.09 \(\pm\) 0.35 b & 57.33 \(\pm\) 9.37 a & 0.98 \(\pm\) 0.53 b & 0.85 \(\pm\) 0.20 a & 1.40 \(\pm\) 0.02 a & 12.23 \(\pm\) 1.47 b & 75.88 \(\pm\) 1.59 a \\ Sandra & 2.78 \(\pm\) 0.40 a & 63.33 \(\pm\) 4.84 a & 1.14 \(\pm\) 0.64 b & 0.95 \(\pm\) 0.05 b & 1.41 \(\pm\) 0.01 a & 12.53 \(\pm\) 1.54 b & 82.15 \(\pm\) 1.92 a \\ \hline \multicolumn{2}{c}{\(p\)-value} & & & & & & \\ \hline N-dose (N) & \textless\text{0.0001} & ns & 0.0069 & 0.0018 & \textless{0.0001} & 0.0095 & ns \\ Variety (V) & \textless\text{0.0001} & ns & 0.0019 & 0.0012 & \textless{0.0001} & 0.0005 & ns \\ N \(\times\) V & \textless\text{0.0001} & ns & \textless{0.0001} & 0.0038 & 0.0276 & 0.0019 & ns \\ interaction & \textless\text{0.0001} & & ns & \textless{0.0001} & 0.0038 & 0.0276 & 0.0019 & ns \\ \hline \end{tabular} Data are presented as means \(\pm\) standard deviations (SD); within columns and factors (N-dose/variety), mean values followed by different letters (A–D for N-dose; a–c for varieties) are significantly different at \(p\) \(<\) 0.05; ns—not statistically significant.  
\end{table} 
Table 3: Phenolic acid concentrations (mg/100 g) in the grain of four barley varieties grown in different conditions of nitrogen fertilization (N-dose) in the controlled field trial in Poland. grains, such as gallic, caffeic, _t_-cinnamic, _p_-coumaric, and sinapic acids, but no differences were found in the content of the dominant ferulic acid (Table 3). The interaction means showing the character of interactions concerning the effect of nitrogen fertilization rate and barley variety on phenolic acid content are presented in Figure 1.  
The Sandra and Galation varieties were characterized by the highest caffeic and _p_-coumaric acid concentrations among the varieties tested. Sandra grain also had the highest _t_-cinnamic acid contents. The Hobbit variety stood out in terms of a higher content of gallic and sinapic acid. Similarly, the Zoom variety was among the richest in sinapic acid (Table 3). As mentioned, the ferulic acid was identified to be a dominant phenolic acid in the tested barley grains. On average, it accounted for approximately 78% of the sum of all identified phenolic acids. This result is closely in line with previous studies showing ferulic and _p_-coumaric acids as the major low-molecular-weight phenolic acids in the grain of barley [33; 55; 56]. Flavonoids are the second group of polyphenols present at high levels in barley grains. They play an important role in cereal plants, contributing to various physiological functions and helping with adaptation to environmental challenges [57; 58].