云南特有两种五层龙属植物的化学成分、抗糖尿病活性及初步作用机制研究

Diabetes Mellitus(DM) occurs through out the world and threatens human health seriously. During the previous scanning anti-diabetes active constituents from natural source, a Yunnan endemic medicinal plant, named Salacia cochinchinensis was found to possess noticeable anti-diabetic activity. Subsequent anti-diabetic bioassay on the plants of Salacia genus suggested the aerial parts of S. polysperma and S. obovatilimba did also exhibit superior hypoglycemic effect. Considering the chemical constituent affinity in the plants from a same genus, TLC and HPLC analyses of the chemical constituents of S. cochinchinensis, S. polysperma and S. obovatilimba were performed. The HPLC chromatograms manifested the chemicals in S. cochinchinensis, S. polysperma were quite different, which suggested study on the two medicinal plants S. cochinchinensis, S. polysperma could avoid obtaining more repeated compounds in the coming examination. A preliminary phytochemical and bioactive investigation on the chemical constituents from S. cochinchinensis displayed there were some anti-diabetic constituents in this plant. Interestingly, some new compounds with novel skeleton isolated from S. cochinchinensis were not being reported in the preceding documents, suggesting the phytochemical and anti-diabetic bioactive investigation was necessary. As we can see, more and more scholars have focused on the bioactive constituents from Salacia genus and there is no investigation on the two Yunnan endemic medicinal plants. Our investigation would be helpful to exploit the valuable ethnic medicinal plants, and provide a series of chemical candidates for the seeking of self-developed antidiabetic agents.

糖尿病对人类健康威胁日益增大，需要新型治疗糖尿病药物。前期研究显示云南特有药用植物柳叶五层龙具有显著降糖活性。在此基础上对云南特有几种五层龙属植物进行了体内抗糖尿病活性筛选，结果显示多籽五层龙和河内五层龙也具有较好降糖活性。同属植物间可能存在相同化学成分，为尽量避免重复分离，采用HPLC对三种具显著降糖活性的五层龙属植物进行分析，最终选择其中成分差异大的柳叶五层龙和多籽五层龙进行化学成分与降糖活性研究。初步研究显示，柳叶五层龙中存在胰岛素增敏和α-葡萄糖苷酶抑制活性的化合物，部分结构新颖。五层龙属植物的化学成分及生物活性研究虽受到日本等国外学者的广泛关注，但由于难以获得相应资源无法开展相关研究；同时前期研究显示该属植物中确实存在降糖活性成分。本项目拟对上述两种云南特有民间药用植物开展化学成分及降糖活性研究，探索其作用机制，为发现具有我国自主知识产权的治疗糖尿病药物提供研究基础。

按照计划任务书要求，本课题在生物活性指导下开展了柳叶五层龙、多籽五层龙的化学成分、降糖活性及初步作用机制研究，从两种药用植物中分离鉴定了99个化合物，化合物类型涉及酚苷、木栓烷、齐敦果烷、熊果烷型等三萜、二萜、木脂素等，类型多样。值得关注的是，我们首次从五层龙属植物中分离鉴定了系列结构较为新颖的dihydro- β- agarofuran型倍半萜。迄今为止，文献报道从该属植物中分离鉴定的该类型倍半萜仅有两个，我们的研究结果较大程度地丰富了该属植物的研究内容。对分离得到的量大成分开展了降糖活性筛选及初步作用机制研究，结果显示：其中的酚苷类和木栓烷型三萜具有显著的α-葡萄糖苷酶抑制活性, 尤其是化合物36和38 对 α⁃葡萄糖苷酶有显著抑制作用， 其 IC50值分别为0.32和 0.59 μmol/L，相关研究结果已经申请中国发明专利；在3T3-L1前脂肪细胞模型上未发现化合物表现出明显的胰岛素增敏作用；有意思的是，我们首次发现系列dihydro- β- agarofuran型倍半萜具有显著抗炎活性，在5μM浓度时其作用均较显著（抑制LPS 诱导产生NO 在60.5-82.3 %之间，与阳性对照地塞米松相当）。耶鲁大学学者在Cell (2015,160:745-758)上发表了一篇关于细胞与胰岛素增敏之间的关系文章，认为“白色脂肪组织炎症易增加不恰当的脂肪溶解、最终导致肝脏乙酰辅酶A水平升高，引起胰岛素抵抗”；同时，马里兰大学医学院学者在JBC (2017，292：12339–12350)上发表炎症中白介素1受体相关激酶1(IRAK-1)通过IL-1受体/Toll样受体介导炎症前体信号传导的研究结果，揭示验证与胰岛素抵抗有关；鉴于我们上述研究结果，将在后续深入的作用机制研究中开展炎症与胰岛素增敏活性的研究，为该类成分作为降糖活性物质提供研究基础。