Preparation and Structural Characterization of Mung Bean RS4·Se (Ⅳ) and Kinetics of Enzymatic Inhibition by It

In this paper, selenized mung bean resistant starch (MB-RS4·Se (Ⅳ)) was prepared from mung bean resistant starch (MB-RS4) by the nitric acid-sodium selenite method. Scanning electron microscopy (SEM) revealed that the starch granules were completely collapsed and fragmented after selenization. The structural characteristics of MB-RS4 and MB-RS4·Se (Ⅳ) were analyzed by ultraviolet (UV) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), gel permeation chromatography (GPC), and nuclear magnetic resonance (NMR). The results showed that selenization resulted in a red shift of the UV peak and a hyperchromic effect. Additionally, the characteristic peaks of Se=O, C-C (Se)₂ and Se-O-C appeared at wavenumbers of 787.88, 730.88 and 654.75 cm^-1, respectively, and the crystal structure was destroyed. The molecular mass dropped significantly, and MB-RS4·Se (Ⅳ)’s configuration was reversed and the C6 position was substituted compared with MB-RS4. MB-RS4·Se (Ⅳ) had a significantly enhanced inhibitory effect on α-glucosidase and α-amylase. The results of the enzymatic reaction kinetics showed that the inhibition of α-glucosidase was competitive type, and the inhibition of α-amylase was mixed anticompetitive type.