College of Food Science and Engineering, Northwest A & F University, China.
Food Funct. 2020 May 1;11(5):3838-3850. doi: 10.1039/c9fo02735a. Epub 2020 Apr 22.
The inhibition of porcine pancreatic α-amylase (PPA) by 9 galloyl-based polyphenols was evaluated via initial digestion velocity, IC, inhibition kinetics, fluorescence quenching and molecular docking studies. The results show that the polyphenols with free galloyl moieties (GMs) exhibited a much higher inhibition effect than that with bound GMs. The inhibition was competitive mode and increased with an increase in the number of free GMs. Interestingly, all the constants that indicate the binding affinity of polyphenols to PPA, including the reciprocal of the competitive inhibition constant (1/K), fluorescence quenching constant (K) and binding energy (E), increased with an increase in the number of free GMs. Besides, the respective order of 1/K, K and E for the galloyl-based polyphenols was contrary to that of IC, indicating that the polyphenol-PPA binding interactions resulted in enzyme inhibition. In addition, the binding interactions were suggested to result from the hydrogen bonding and π-π conjugation forces between the free GMs and amino acid residues at the active sites of PPA, whereas the chemical linkage of the GMs with additional polyphenol groups limited these interactions. Furthermore, the hypoglycemic effects of two polyphenols with 5 free GMs indicate that GMs may be considered a functional fragment involved in the alleviation of the symptoms of type II diabetes through α-amylase inhibition.
通过初始消化速度、IC、抑制动力学、荧光猝灭和分子对接研究评估了 9 种没食子酰基多酚对猪胰腺α-淀粉酶（PPA）的抑制作用。结果表明，具有游离没食子酰基（GMs）的多酚表现出比结合 GMs 的多酚更高的抑制效果。抑制为竞争模式，随着游离 GMs 数量的增加而增加。有趣的是，所有表明多酚与 PPA 结合亲和力的常数，包括竞争性抑制常数（1/K）、荧光猝灭常数（K）和结合能（E）的倒数，都随着游离 GMs 数量的增加而增加。此外，对于没食子酰基多酚，1/K、K 和 E 的顺序与 IC 相反，表明多酚-PPA 结合相互作用导致酶抑制。此外，结合相互作用可能是由于游离 GMs 与 PPA 活性位点的氨基酸残基之间的氢键和π-π共轭力所致，而 GMs 与其他多酚基团的化学连接限制了这些相互作用。此外，两种具有 5 个游离 GMs 的多酚的降血糖作用表明，GMs 可能被认为是一种功能片段，通过抑制α-淀粉酶缓解 II 型糖尿病的症状。
