Hypericum attenuatum Choisy is a traditional Chinese herbal plant with multiple therapeutic effects. In this study, bioactivity-guided fractionation of Hypericum attenuatum Choisy extracts afforded three major flavonoids (including astragalin, guaijaverin and quercetin), which possessed α-Glucosidase inhibitory activity with IC₅₀ values of 33.90±0.68 μM, 17.23±0.75 μM and 31.90±0.34 μM, respectively. Circular dichroism analysis revealed that all the three compounds could interact with α-glucosidase by inducing conformational changes of the enzyme. Molecular docking results indicated that they could bind to the active site in α-glucosidase, and the binding force was driven mainly by hydrogen bond. Additionally, isobolographic analysis of the interactions between two compounds showed that all the combinations presented a synergistic α-glucosidase inhibitory effect at lower concentrations, and the combination between quercetin and guaijaverin or astragalin exhibited the best synergistic effect. This research might provide a theoretical basis for the application of Hypericum attenuatum Choisy in treating hyperglycemia.

中文翻译：

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金丝桃中主要黄酮类化合物的α-葡萄糖苷酶抑制作用及其协同作用

金丝桃是一种具有多种治疗作用的传统中草药植物。在这项研究中，生物活性引导下的金丝桃提取物分馏提供了三种主要的黄酮类化合物（包括黄芪甲苷、番石榴甙和槲皮素），它们具有 α-葡萄糖苷酶抑制活性，IC ₅₀值分别为 33.90±0.68 μM、17.23±0.75 μM 和 31.90±0.34 μM。圆二色性分析表明，所有三种化合物都可以通过诱导酶的构象变化与α-葡萄糖苷酶相互作用。分子对接结果表明它们可以与α-葡萄糖苷酶的活性位点结合，结合力主要由氢键驱动。此外，两种化合物相互作用的等效线谱分析表明，所有组合在较低浓度下均表现出协同的α-葡萄糖苷酶抑制作用，其中槲皮素与愈创木酚或黄芪甲苷的组合表现出最佳的协同作用。本研究可能为金丝桃在治疗高血糖中的应用提供理论依据。