Xiao Huizhi, Liu Benguo, Mo Haizhen, Liang Guizhao
Key Laboratory of Biorheological Science and Technology, Ministry of Education, School of Bioengineering, Chongqing University, Chongqing 400044, PR China.
School of Food Science, Henan Institute of Science and Technology, Xinxiang 453003, PR China.
Food Res Int. 2015 Oct;76(Pt 3):605-610. doi: 10.1016/j.foodres.2015.07.029. Epub 2015 Jul 22.
In this work, the inhibitory effects of tannic acid on the α-glucosidase and trypsin were systematically evaluated by comparing with the clinical diabetes healer acarbose and the soybean-derived trypsin inhibitor using fluorescence spectroscopy and enzymatic kinetics methods. We showed that the anti-α-glucosidase activity of tannic acid (IC=0.44μg/mL) was higher than that of acarbose (IC>0.60μg/mL), while its anti-trypsin activity (IC=0.79mg/mL) was significantly lower than that of the trypsin inhibitor from soybean (IC<0.20mg/mL). Enzymatic kinetics measurements confirmed that the inhibitory pattern of tannic acid toward two tested enzymes was a mixed competitive and noncompetitive inhibition. Tannic acid could bind the enzymes to form new complexes, presenting a strong static fluorescence quenching. The presence of tannic acid led to the hypsochromic shift of the maximum fluorescence in trypsin, but not in α-glucosidase. The thermodynamic parameters indicated that the main driving force between tannic acid and both the enzymes was the hydrophobic interaction followed by the electrostatic interaction. Our work suggests that tannic acid is a strong anti-α-glucosidase natural inhibitor with a low inhibitory activity for trypsin, thus its roles in functional food and medicinal plants should be re-recognized.
在本研究中，通过荧光光谱法和酶动力学方法，与临床糖尿病治疗药物阿卡波糖及大豆来源的胰蛋白酶抑制剂进行比较，系统评估了单宁酸对α-葡萄糖苷酶和胰蛋白酶的抑制作用。我们发现，单宁酸的抗α-葡萄糖苷酶活性（IC = 0.44μg/mL）高于阿卡波糖（IC>0.60μg/mL），而其抗胰蛋白酶活性（IC = 0.79mg/mL）显著低于大豆胰蛋白酶抑制剂（IC<0.20mg/mL）。酶动力学测量证实，单宁酸对两种受试酶的抑制模式为混合型竞争和非竞争抑制。单宁酸可与酶结合形成新的复合物，呈现出强烈的静态荧光猝灭。单宁酸的存在导致胰蛋白酶最大荧光峰发生蓝移，而α-葡萄糖苷酶未出现此现象。热力学参数表明，单宁酸与两种酶之间的主要驱动力是疏水相互作用，其次是静电相互作用。我们的研究表明，单宁酸是一种强效的抗α-葡萄糖苷酶天然抑制剂，对胰蛋白酶的抑制活性较低，因此其在功能性食品和药用植物中的作用应重新认识。
