The content of free, conjugated and bound phenolic acids in 12 wheat (Triticum aestivum L.) genotypes of 4 different grain colours (standard red, yellow endosperm, purple pericarp and blue aleurone) from 2-year field trial was analysed in the present study. Significant increase (8%) in the total phenolic acid content was observed in the dryer year 2017. Five phenolic acids (ferulic, sinapic, p-coumaric, vanillic and 4-hydroxybenzoic) and cis-isomers of ferulic and sinapic acid were determined by HPLC-DAD (high-performance liquid chromatography with a diode-array detector) in grain samples. The total phenolic acid content of coloured wheat groups varied: blue aleurone > purple pericarp > yellow endosperm > red colour (798 > 702 > 693 > 599 µg/g). The fraction of bound phenolic acids was the major contributor to the total phenolic acid content (91.7%) with ferulic acid predominating (85.2%). Conjugated phenolic acids accounted for 7.9% of the total with sinapic and ferulic acid predominating (47.6% and 19.9%). The composition of individual phenolic acids was similar within these two fractions. The remaining 0.4% was represented by the fraction of free phenolic acids in which the phenolic acid profile varied among the individual coloured groups. Ferulic acid prevailed in red and yellow wheats, vanillic in blue and p-coumaric in purple wheats.

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The total antioxidant activity (TAA), total contents of polyphenols (TPC), phenolic acids (TPA) and tocols (TTC) were determined in the grain of 5 oat cultivars of Czech origin grown under organic and conventional cropping systems in two-year experiments (2018 and 2019). The TPC ranged from 772.9 mg/kg DM (dry matter) (hulled oat cv. Seldon) to 890.6 mg/kg (naked oat cv. Patrik); the TPA from 261.6 mg/kg (cv. Seldon) to 479.0 mg/kg (cv. Patrik); the TTC from 110.9 mg/kg (hulled oat cv. Korok) to 126.5 mg/kg (cv. Seldon). The TAA ranged from 427.1 mg/kg (cv. Korok) to 474.9 mg/kg (cv. Seldon). Besides the effect of the cultivar, the TAA and antioxidant contents were significantly affected also by year (weather conditions); higher values were observed in the drier and warmer the year 2019. The effect of the cropping system was statistically insignificant.