Abstract: Layered milling technique combined with targeted metabolomics was applied to analyze the characteristic components including carotenoids and secondary metabolites including phenolic compounds from different parts of corn kernel, and the antioxidant activities of these parts were studied. The results showed carotenoids mainly existed in the aleurone layer and peripheral endosperm of corn kernel, while phenolic compounds existed in the pericarp, seed coat and aleurone layer mostly in a bound form. Totally 17 free phenolic acids were detected in each separated part, with the most abundant ones being vanillin, 4-hydroxybenzoic acid and ferulic acid. The antioxidant activity of each part of corn kernel was positively correlated with the contents of phenolic compounds (P < 0.01), and at individual phenolic acid level, vanillin, 4-hydroxybenzoic acid and syringaldehyde were the major contributors to the antioxidant activity of corn kernel. The antioxidant activity of the inner bran layer was relatively higher than that of the other parts.

Key words: corn kernel; layered milling; secondary metabolites; phenolic phytochemicals; carotenoids; antioxidant activity