Study on extraction and purification of flavonoids from corn silk and its inhibitory effect on starch digestive enzymes

Postprandial hyperglycemia represents a critical challenge for individuals with diabetes. Inhibiting the activity of starch digestive enzymes can effectively delay starch digestion, thereby regulating postprandial blood glucose levels. Crude flavonoids were extracted from corn silk and subsequently purified using AB-8 macroporous resin and polyamide resin for fractional purification. Their composition was analyzed using liquid chromatography, and their inhibitory activity against α-amylase and α-glucosidase was investigated through kinetic and fluorescence spectroscopy methods. Results demonstrated that the purity of flavonoids increased from 5.16% to 23.19% after purification with AB-8 resin and further rose to 38.42% after purification with polyamide resin, representing a 6.4-fold enhancement. Liquid chromatography analysis revealed that polyamide-purified fraction Ⅱ constituted the primary flavonoid component. Inhibition assays indicated that polyamide-purified flavonoids exhibited the strongest inhibitory effects, with IC₅₀ values of 0.768 mg/mL and 0.017 mg/mL for α-amylase and α-glucosidase, respectively. Kinetic parameters revealed that the K_ic values of polyamide-purified flavonoids for α-amylase and α-glucosidase were 4.02 mg/mL and 0.45 mg/mL, respectively, indicating stronger inhibitory activity against α-glucosidase. Spectroscopic analysis suggests that inhibition was primarily achieved through hydrogen bonding, hydrophobic interactions, and van der Waals forces. In summary, flavonoids derived from corn silk demonstrate significant potential to inhibit starch digestive enzymes and may serve as adjunct for regulating postprandial blood glucose levels.