Carotenoid and Phenolic Compositions and Antioxidant Activity of 23 Cultivars of Corn Grain and Corn Husk Extract

As a byproduct of corn processing, corn husk is usually burned or disposed of. To make a better use of corn husk, its bioactive components need to be further explored. In this work, the carotenoids and phenolics of the extracts from the corn grain and corn husk of 15 different yellow corn and 8 different waxy corn were identified and quantified, and their antioxidant activities were assessed. The results showed many considerable variations in carotenoid contents. Four types of carotenoids were observed only in both yellow corn and black waxy corn. The highest lutein and zeaxanthin contents were both observed in yellow corn husks. Lutein dominates in yellow corn, ranging from 494.5 μg/g dw to 2870.8 μg/g dw, which is followed by zeaxanthin, ranging from 63.0 μg/g dw to 360.2 μg/g dw, and finally β-cryptoxanthin and β-carotene. The total content of polyphenols (TPC) and flavonoids (TFC) of the husk from 13 yellow corn cultivars, as well as the TPC of husk from 8 waxy corn cultivars, were all higher than those of their corn grain, with the highest TPC found in waxy corn husk. Additionally, a total of 20 phenolic compounds were identified, and ferulic acid showed the highest content and reached 1101.9 µg/g dw in a waxy corn husk. The average antioxidant activity of a waxy corn husk was 25-65% higher than that of a yellow corn husk, and the highest values were observed in the husk of the waxy corn cultivar Huhong 1. These results suggested that corn husk is a rich source of lutein and phenolics and provided excellent cultivars as a reference for functional food products in agriculture and the food industry.