Key Laboratory of Chemical Biology and Molecular Engineering of the Ministry of Education, Shanxi University, Taiyuan, 030006, China.
J Agric Food Chem. 2009 Dec 23;57(24):11463-8. doi: 10.1021/jf903083h.
Three flavonoids from tartary buckwheat bran, namely, quercetin (Que), isoquercetin (Iso) and rutin (Rut), have been evaluated as alpha-glucosidase inhibitors by fluorescence spectroscopy and enzymatic kinetics and have also been compared with the market diabetes healer, acarbose. The results indicated that Que, Iso and Rut could bind alpha-glucosidase to form a new complex, which exhibited a strong static fluorescence quenching via nonradiation energy transfer, and an obvious blue shift of maximum fluorescence. The sequence of binding constants (K(A)) was Que > Iso > Rut, and the number of binding sites was one for all of the three cases. The thermodynamic parameters were obtained by calculations based on data of binding constants. They revealed that the main driving force of the above-mentioned interaction was hydrophobic. Enzymatic kinetics measurements showed that all of the three compounds were effective inhibitors against alpha-glucosidase. Inhibitory modes all belonged to a mixed type of noncompetitive and anticompetitive. The sequence of affinity (1/K(i)) was in accordance with the results of binding constants (K(A)). The concentrations which gave 50% inhibition (IC(50)) were 0.017 mmolL(-1), 0.185 mmolL(-1) and 0.196 mmolL(-1), compared with acarbose's IC(50) (0.091 mmolL(-1)); the dose of acarbose was almost five times of that of Que and half of that of Iso and Rut. Our results explained why the inhibition on alpha-glucosidase of tartary buckwheat bran extractive substance (mainly Rut) was much weaker than that of its hydrolysis product (a mixture of Que, Iso and Rut). This work would be significant for the development of more powerful antidiabetes drugs and efficacious utilization of tartary buckwheat, which has been proved as an acknowledged food in the diet of diabetic patients.
三种来自鞑靼荞麦麸皮的类黄酮，即槲皮素（Que）、异槲皮苷（Iso）和芦丁（Rut），已通过荧光光谱法和酶动力学评估为α-葡萄糖苷酶抑制剂，并与市场上的糖尿病治疗药物阿卡波糖进行了比较。结果表明，Que、Iso 和 Rut 可以与 α-葡萄糖苷酶结合形成新的复合物，通过非辐射能量转移表现出强烈的静态荧光猝灭，并且最大荧光发生明显蓝移。结合常数（K(A)）的顺序为 Que > Iso > Rut，并且所有三种情况下的结合位点数均为一个。根据结合常数的数据计算得到热力学参数。结果表明，上述相互作用的主要驱动力是疏水的。酶动力学测量表明，所有三种化合物都是有效的α-葡萄糖苷酶抑制剂。抑制模式均属于非竞争性和反竞争性的混合类型。亲和性（1/K(i)）的顺序与结合常数（K(A)）的结果一致。达到 50%抑制的浓度（IC(50)）分别为 0.017 mmolL(-1)、0.185 mmolL(-1)和 0.196 mmolL(-1)，而阿卡波糖的 IC(50)为 0.091 mmolL(-1)；阿卡波糖的剂量几乎是 Que 的五倍，是 Iso 和 Rut 的一半。我们的结果解释了为什么鞑靼荞麦麸皮提取物（主要是 Rut）对α-葡萄糖苷酶的抑制作用远弱于其水解产物（Que、Iso 和 Rut 的混合物）。这项工作对于开发更有效的抗糖尿病药物以及有效利用已被证明是糖尿病患者饮食中公认的食物的鞑靼荞麦具有重要意义。
