Unveiling the hypoglycemic of hesperetin-Cu(II) complex: impact on the physicochemical properties and digestibility of gelatinized corn starch

Starch intake is the main cause of postprandial hyperglycemia. This study aimed to investigate the effect of hesperetin-copper (II) complex [Hsp-Cu(II)] on the physico-chemical properties and digestibility of gelatinized corn starch (GCS). It was found that with the addition of 1.44 mg/mL Hsp-Cu(II), the digestion rate of GCS decreased from 87.0% to 52.2%, the rapidly digestible starch content reduced from 22.7% to 14.4%, and the resistant starch content increased from 18.1% to 55.0%, suggesting that Hsp-Cu(II) decreased the digestion rate of GCS by increasing the content of resistant starch. The analysis of X-ray diffraction, rheology and differential scanning calorimetry showed that Hsp-Cu(II) increased the crystallinity, viscosity, storage modulus (G′), loss modulus (G′′) and thermal stability of GCS. Fourier transform infrared spectroscopy found that Hsp-Cu(II) bound with GCS through hydrogen bonds. In addition, scanning electron microscopy showed that Hsp-Cu(II)‒GCS complex possessed a denser structure, thicker crystalline flakes and thinner amorphous flakes in comparison with GCS. Therefore, Hsp-Cu(II) may inhibit the digestion of GCS by changing the physicochemical properties and increasing the content of resistant starch of GCS, and inhibiting the activities of α-amylase and α-glucosidase at the same time by hindering the binding of GCS to the enzymes. These findings have demonstrated the potential ability of Hsp-Cu(II) to lower the level of postprandial blood glucose. This study may provide new insights into the development of Hsp-Cu(II) as a novel anti-diabetic nutritional supplement.