金银花花蕾中3,5-二咖啡酰奎宁酸对α-葡萄糖苷酶抑制作用的研究

本研究探讨金银花花蕾中3,5-二咖啡酰奎宁酸（3,5-DCQA）对α-葡萄糖苷酶的抑制作用。通过色谱方法从金银花花蕾50%甲醇提取物中分离获得3,5-DCQA，并用质谱与核磁等光谱分析对其化学结构进行鉴定。分别选取大鼠小肠I型及酿酒酵母、面包酵母、嗜热脂肪芽孢杆菌的II型α-葡萄糖苷酶研究3,5-DCQA对不同α-葡萄糖苷酶抑制活性的选择性，结果表明该物质对α-葡萄糖苷酶的抑制作用与酶的来源有关，并选择性地抑制小肠α-葡萄糖苷酶的麦芽糖水解活性。动力学实验结果揭示3,5-DCQA非竞争性地抑制小肠麦芽糖酶活性（Ki：0.22 mM）。此外，物质结构与活性关系（SAR）的研究显示，3,5-DCQA中咖啡酰氧基团数目与活性有关，其中所含两个咖啡酰氧基团对α-葡萄糖苷酶的抑制活性起关键性作用。因此金银花花蕾中的3,5-DCQA可用于辅助降低餐后高血糖类功能食品的开发与利用。
Inhibitory effect of 3,5-dicaffeoylquinic acid (3,5-DCQA) from flower buds of Lonicera japonica Thunb on α-glucosidase was investigated. The 3,5-DCQA was isolated from a 50%-methanol extract of L. japonica flower buds using chromatography and its structure was identified by mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy. The selectivity of 3,5-DCQA in its inhibition of ?-glucosidase was evaluated using ?-glucosidase I from rat small intestine and ?-glucosidase II from Saccharomyces cerevisiae, baker’s yeast, and Bacillus stearothermophilus. The result indicated that the degree of ?-glucosidase inhibition by 3,5-DCQA was related to the origin of the enzyme. In addition, 3,5-DCQA selectively inhibited maltose hydrolysis activity of rat intestinal ?-glucosidase I. Kinetic study revealed that 3,5-DCQA was a noncompetitive inhibitor of rat intestinal maltase with a Ki value of 0.22 mM. Furthermore, the structure-activity relationship (SAR) study suggested that the two caffeoyl groups in 3,5-DCQA play an essential role in ?-glucosidase inhibitory activity and that the number of caffeoyl groups in 3,5-DCQ are related to its activity. Therefore, 3,5-DCQA obtained from the flower buds of Lonicera japonica Thunb can be used in development and application of functional foods for the management of postprandial hyperglycemia.