水甘草碱及柯南因-依波加聚合体生物碱结构优化与抗肿瘤作用机制研究

Presently, screening target agents is one goal of anticancer drug discovery. Preliminary research indicated that dimeric and monomeric aspidosperma (Asp) type alkaloids possessed better cytotoxicity in monoterpenoid indole alkaloids. Analysis of structure-activity relationship of aspidosperma type alkaloids and their dimers suggested that tabersonine (TA) was base skeleton,and the oxopropyl at C-3 and dihydroxyl at C-14/15 were pharmacophores. Further experiement showed that activities of four 14,15-dihydroxy-TA derivatives by semi-synthesis were improved significantly compared with those with 14,15-epoxy moiety. Additionally, one of them, 3-oxopropyl-14a,15a-dihydroxy-TA could inhibit topo IIa other than topo I. It could downregulate Bcl-2 and upregulate Bak and Bax tumor cell. Furthermore, corynanthe-iboga (Cy-Ib) type dimers also showed good anticancer activity in vivo, especially new Cy-Ib dimers with N-C-O six-membered ring indicated not only better cytotoxity against cancer cells but selectivity to A-549 cell. This project will continue structural optimization of TA, and undertake research of anticancer machanism and structure-activity relationship of the new Cy-Ib dimers, aiming to anticancer targeted molecules.

寻找靶向分子是当前抗肿瘤药物研发的主要内容之一。前期研究发现单萜吲哚生物碱中的白坚木碱类(Asp)、白坚木-白坚木碱类二聚体具有较强细胞毒活性。分析发现能统一Asp及其二聚体的构效关系：即水甘草碱（TA）是基本骨架，C-3烷基化、C-14/15双羟基、C-11甲氧基是重要的药效团。活性研究证实4个半合成的14,15-二羟基TA衍生物细胞毒活性显著提高，其中3-丙酮基-14,15-二羟基TA能选择性抑制Topo IIa；能诱导肿瘤细胞凋亡，引起抗凋亡蛋白Bcl-2下调，促凋亡蛋白Bak和Bax上调。另外，柯南因-依波加碱(Cy-Ib)二聚体在体内、外模型上显示较好的抗肿瘤活性，具有N-C-O六元环新型Cy-Ib二聚体活性更强，且对肿瘤细胞具有一定的选择性,推测该六元环是新的助效团。本项目将继续完善TA的结构优化与机制研究，探讨新型Cy-Ib类聚合体抗肿瘤作用机制与构效关系，寻找靶向活性分子。

项目执行期间从10种植物和结构修饰生得到94个白坚木碱类成分，其中新成分32个，基本代表了该类生物碱主要位置变化情况。同时，从植物中发现柯南因—依波加碱聚合体成分21个，其中新成分13个。还发现30个结构新颖、骨架重拍、延长/降解的单萜吲哚生物碱，进一步丰富了单萜吲哚生物碱结构多样性。部分成分显示很好的抗肿瘤活性，一定程度上认识了这些生物碱抗肿瘤活性的基本骨架、取代基及构效规律。在构效规律的指引下，进一步寻找候选分子2类。开展了3个活性成分的作用机制探索，研究结果表明柯南因—依波加碱聚合体和单体水甘草碱类抗肿瘤机制主要是微管蛋白聚合的抑制剂，其中单体水甘草碱衍生物类可以作为长春碱类药物结构简化的途径。首次发现白坚木碱二聚体抗肿瘤活性与肿瘤免疫直接相关，这在抗肿瘤然天然小分子成分中十分罕见的。研究成果已发表SCI论文6篇，申请国家发明专利3项，其中2项已授权，培养硕士、博士研究生4人。