可溶性食物繊維と黒糖ポリフェノールの非共有結合相互作用がα-グルコシダーゼ阻害活性に及ぼす影響

Soluble dietary fibers (SDFs) and polyphenols inhibit α-glucosidase, and their coexistence in foods could interactively affect their inhibition activity. This study investigated the α-glucosidase inhibitory effects of four SDFs (polygalacturonic acid, xylan, oat β-glucan, and dextran) individually, as well as in combination with brown sugar polyphenols (BSPs, which include chlorogenic acid, p-coumaric acid, and ferulic acid), to assess their interactive effects on inhibition. The evaluation was conducted through the analysis of half-maximal inhibitory concentration (IC₅₀), molecular docking, molecular dynamics (MD), Molecular Mechanic/Poisson-Boltzmann Surface Area (MM-PBSA), inhibition kinetics, and fluorescence quenching. Polygalacturonic acid and xylan inhibited the enzyme with IC₅₀ values of 4.68 mg/mL and 10.44 mg/mL, respectively, while oat β-glucan and dextran showed no inhibition. The combination of polygalacturonic acid and xylan with BSPs significantly enhanced α-glucosidase inhibition. Notably, polygalacturonic acid combined with chlorogenic acid showed an IC₅₀ of 0.45 mg/mL, lower than acarbose (0.61 mg/mL). However, oat β-glucan and dextran combined with BSPs reduced the individual potency of BSPs. The enhancement and attenuation may result from SDF-BSP interactions, as evidenced by inhibition kinetics and fluorescence quenching analyses. Furthermore, X-ray powder diffraction, Fourier transform infrared spectroscopy, hydrogen nuclear magnetic resonance, and molecular docking analyses showed that SDFs interact with BSPs via non-covalent bonds. This study is valuable for both SDFs and BSPs as natural inhibitors of α-glucosidase.