Temperature-dependent modulation of structural characteristics and α-glucosidase inhibitory activity of corn bran...

Corn bran polysaccharide (CBP) was extracted by water extraction followed by ethanol precipitation. Methylation analysis indicated that CBP mainly contained terminal Araf-(1→, →3,4)-Xylp-(1→, and →4)-Xylp-(1 → residues, together with minor →4,6)-Glcp-(1→, →3)-Galp-(1→, and Galp-(1 → residues. A non-covalent CBP-quercetin (CBP-QC) complex was prepared by thermal induction, and its structural characteristics and α-glucosidase inhibitory activity were systematically investigated. Among the tested temperatures, complexation at 65 °C resulted in the higher quercetin-binding capacity and stronger α-glucosidase inhibitory activity. FT-IR analysis revealed a shift of the OH stretching band around 3300 cm^-1, while XRD showed a decrease in the characteristic diffraction peak at 2θ = 19°, supporting an association between CBP and QC. CBP-QC exhibited reversible mixed-type inhibition against α-glucosidase, with fluorescence analysis suggesting predominantly static quenching. Thermodynamic parameters indicated a spontaneous interaction, with hydrogen bonding potentially contributing to the binding process. Furthermore, the CBP-QC complex improved glucose metabolism in IR-HepG₂ cells. These findings showed that thermal treatment modulated the structural characteristics and α-glucosidase inhibitory activity of CBP-QC, providing preliminary insights into its potential as a natural functional food ingredient.