Phenolic antioxidants of foxtail and little millet cultivars and their inhibitory effects on α-amylase and α-glucosidase activities

•Millet cultivars showed variations in the soluble and bound phenolic contents.•Ferulic, sinapic and caffeic acids were most abundant in the soluble fractions.•Apigenin, kaempferol and luteolin were principal flavonoids in millet cultivars.•Foxtail and little millet fractions displayed multiple antioxidant activities.•Soluble and bound phenolics were potent α-amylase and α-glucosidase inhibitors. Evaluation of phenolic contents and their in vitro bioactivities of six diverse cultivars of foxtail and little millets revealed that their total phenolic content ranged from 19.42 to 24.12 µmol ferulic acid equivalents/g. The soluble fraction accounted for more than 80% of the total phenolic and flavonoid contents. Ferulic, caffeic and sinapic acids were the predominant phenolic acids, and luteolin and kaempferol were major flavonoids in the soluble fractions of millets. However, ferulic and p-coumaric acids were abundant in the bound fractions. Millet cultivars exhibited relevant changes in antioxidant activities in different mechanisms. Little millet cultivars showed superior inhibition of α-amylase and α-glucosidase than foxtail millet cultivars. The soluble and bound fractions of CO7 cultivar of foxtail millet (IC50, 22.37 and 57.26 µg/ml) and CO4 cultivar of little millet (IC50, 18.97 and 55.69 µg/ml) displayed strong inhibition towards α-glucosidase. These results suggest the potential application of underutilized millets as functional food ingredients for regulating postprandial hyperglycemia.