Phenolic composition and antioxidant activity of colored oats

•28 soluble phenolics including cinnamoylglycerides were detected.•10 bound phenolics were identified.•An increased antioxidant activity of hulls compared to groats was observed.•The black-hulled samples were different from the white ones.•A distinction between spring and winter cultivars was found. Phenolic composition and antioxidant capacity of 20 oat genotypes differing in hull color were investigated. Phenolic aldehydes, phenolic acids, avenanthramides and mono-, and diglycerides were identified in the soluble phenolic fraction of the genotypes. The bound phenolic fraction proved to be less diverse with phenolic aldehydes, phenolic acids and a ferulic acid dehydrodimer detected. Investigating the scavenging capacity of the hull and groat toward 2,2-diphenyl-1-picrylhydrazyl (DPPH), an increased antioxidant activity (AOA) of hull compared to groats and a color dependence of the hull AOA could be observed. Principal component analysis on the determined variables revealed that the black-hulled samples were different from the white ones due to their increased phenolic content detected in the hull. However, reddish-hulled varieties were grouping with the accessions of the other colored groups. In addition, a distinction between spring and winter cultivars was also observed.