Phenolic acids in kernels of different coloured-grain wheat genotypes

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 HPI.C-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 mu g/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.