海南蒲桃抑制α-葡萄糖苷酶活性多酚类成分的发现及其降血糖作用研究

Alpha glucosidase inhibitor is a very important target for antidiabetic drug discovery. Currently, it’s also the first choice for many type 2 diabetes patients in clinical therapy. In recent years, food-derived α-glucosidase inhibitors attracted more and more attention due to lower toxicity and fewer side effects against hyperglycemia compared with synthetic drugs. Syzygium cuminii (L.) Skeels [Eugenia jambolana Lam.] has a long history for treating diabetes as folk medicine; the fruit of Syzygium c. is an edible berry with deep color. According to our previous study, both of the fruit and seed extracts of Syzygium c. are rich in polyphenols. Moreover, several identified polyphenols from the seeds extracts exhibit significant inhibitory activity against α-glucosidase, some of them are stronger than acarbose, which is a clinical antidiabetic medicine in the market. These results suggest Syzygium c. is a potential functional food candidate and good resource for α-glucosidase inhibitor. In the present project, we propose to seek novel bioactive polyphenols from the fruit and seed extracts of Syzygium c. under the guide of bioassay result. Plants were collected from Yunnan, China; Multi-chromatography and spectral analysis will be utilized to isolate and identify phenolics from crude extracts; The isolates will be submitted to α-glucosidase and α-amylase enzyme inhibitory bioassay in vitro, and the active compounds will be given to ob/ob mice to evaluate their effects on reducing blood glucose and improving carbohydrate tolerance activity in vivo; In addition, biological markers of experimental animals’ organs, such as liver, kidney, etc. will be examined coupled with histological observation of tissues. The current research would provide insights into α-glucosidase inhibitory effects of phenolic-enriched Syzygium c. extracts, discover novel leading compounds for anti-diabetes and improve the development and usage of Syzygium c. as functional food.

α-葡萄糖苷酶抑制剂一直是降糖药物研发的重点，其中食源性的α-葡萄糖苷酶抑制剂由于其安全、有效的特点引发了越来越多的关注。海南蒲桃Syzygium cuminii (L.) Skeels果实可食，产量大，在民间用于治疗糖尿病。项目组对海南蒲桃的初步研究显示，其果实及种子提取物富含多酚类成分；前期从种子中分离鉴定的部分多酚类化合物对α-葡萄糖苷酶抑制活性优于阿卡波糖，表明海南蒲桃是发现α-葡萄糖苷酶抑制剂的优质资源。本研究拟以α-葡萄糖苷酶抑制活性为指导，通过现代色谱及波谱技术从海南蒲桃果实及种子多酚提取物中分离鉴定抑制葡萄糖苷酶活性成分；对活性化合物在ob/ob转基因小鼠中进行降低血糖及改善糖耐量的活性评价，并对小鼠脏器生化指标及组织形态学变化进行检测。以期发掘海南蒲桃中对人体健康有益的降血糖活性成分，发现结构新颖的降血糖药物先导化合物，为其作为功能性食品的开发和利用提供科学依据。

α-葡萄糖苷酶抑制剂一直是降糖药物研发的重点，其中食源性的α-葡萄糖苷酶抑制剂由于其安全、有效的特点引发了越来越多的关注。海南蒲桃又称乌墨、印度黑莓，为桃金娘科蒲桃属常绿乔木，在我国台湾、福建、广东、广西、云南等地均有分布。海南蒲桃果实可食，在民间被作为传统降血糖药食两用植物而使用。该植物果实、种子、树皮、叶子等部位都被报道具有降血糖活性，然而对于其活性物质基础的研究却相对不足，对单体化合物活性及作用机制的研究更为缺乏，阻碍了海南蒲桃作为降糖功能性食品的推广及进一步的开发利用。在青年基金的支持下，本项目围绕①海南蒲桃中α-葡萄糖苷酶抑制活性多酚类成分发现；②单体化合物及活性组分的降血糖体内外生物活性评价；③海南蒲桃中主要多酚类成分体内代谢产物的生物活性研究开展了相关工作。迄今为止，本课题从海南蒲桃果实及种子中分离鉴定了活性多酚类化合物近40个，其中16个化合物为未经文献报道的新化合物，研究结果丰富了海南蒲桃天然产物的结构类型。体外活性筛选结果表明，海南蒲桃中含有的鞣花酸衍生物具有良好的α-葡萄糖苷酶抑制活性，多个化合物对该酶抑制效果优于阳性药物阿卡波糖。同时本项目对海南蒲桃果实的研究首次揭示了其含有的三萜类成分具有降血糖的功效。此外，通过对主要成分鞣花酸体内代谢产物urolithin类物质的生物活性研究，揭示了海南蒲桃在糖尿病并发症预防与治疗中的应用潜力。本项目的研究工作在一定程度上解决了海南蒲桃，尤其是其可食用果实降血糖活性成分及作用机制不明的问题，为其作为功能性食品的开发和利用提供了科学依据和实验基础。同时本项目的研究结果有助于推动天然来源的α-葡萄糖苷酶抑制剂的发现，为开发具有我国自主知识产权的具有辅助降血糖功效的膳食营养补充剂奠定实验基础。