Regulation of Glucose Uptake Level by Black Corn-Derived Anthocyanins at the Small Intestinal α-Glucosidases and Different Types of Glucose Transporters

Attenuating the postprandial glycemic spike is crucial for managing blood-glucose homeostasis and mitigating chronic diseases. The structural and functional properties of anthocyanins from black corn (Zea mays L.), and their role in modulating glucose uptake by regulating digestive enzymes and glucose transporters via their multiple hydroxyl groups, were investigated. Among the purified anthocyanins with significant antioxidant activity in ABTS+ and DPPH assays, cyanidin, pelargonidin, and peonidin were dominant, as indicated by HPLC-MS analysis. Based on the IC50 values, black corn anthocyanins effectively inhibited mammalian α-glucosidases, reducing glucose generation from α-1,4-linked glycemic carbohydrates. In a Caco-2 cell model, anthocyanins reduced the glucose-transport efficiency and downregulated the mRNA expression of key glucose-transporter-related genes. ICR male mice orally administered the purified anthocyanins showed significantly attenuated glycemic responses to α-1,4-linked carbohydrates (p < 0.05). Thus, black corn anthocyanins exhibit promising properties as functional ingredients for the regulation of postprandial blood glucose levels.