川山橙中白坚木类生物碱诱导肿瘤细胞凋亡的作用机制和构效关系研究

Chemotherapeutics is one of the main clinical therapies of tumor, but the serious side effects, which greatly restricted the chemotherapy drug application. Therefore, finding and developing effective antitumor drugs is be great significant. Between 1940 and 2006 years, more than 155 small molecule antitumor drugs were developed, which 47 percent were natural drug extracts or their derivatives. Melodinus hemsleyanus is a member of the genus Melodinus, which used as traditional Chinese medicine for the treatment of carbuncle and sore in the mouth. In our investigation of active component from the M. hemsleyanus, we found that the total alkaloids exhibited significant antitumor activities. The IC50 value of compound 1 to HepG2 cells was 2.3μM/L, which was 8.6 times better than those of cisplatin. The mechanisms could be induced apoptosis through activations of caspase protein. In the present study, we will carry out the isolation and structural elucidation of alkaloids from M. hemsleyanus, as well as study the biological targets of their anti-tumor activity from inducing apoptosis. Our study will further demonstrate the structure-function relationships and molecular mechanism of anti-tumor activity of alkaloids, which will provide the powerful evidence for the development of new antitumor drug.

化疗是治疗肿瘤最常见的手段之一，但严重的毒副作用限制了其临床应用。因此，寻找高效低毒的抗肿瘤药物具有重要意义。从1940年到2006年开发的155种小分子抗肿瘤药中，有47%是天然药物提取物或其衍生物。川山橙(Melodinus hemsleyanus)为夹竹桃科山橙属植物，有清热解毒之功效，民间常用于治疗痈肿疮毒、口舌生疮等症。本课题组前期对川山橙的化学成分研究中，发现总生物碱具有明显的抗肿瘤活性，化合物1对HepG2细胞的IC50值为2.3μM/L，优于阳性对照药顺铂的8.6倍。初步的作用机制研究表明可能是通过活化caspase家族蛋白诱导细胞凋亡来发挥抗肿瘤作用，但具体的作用位点及作用方式尚不清楚。本项目拟在前期工作的基础上，进一步对川山橙中的生物碱类成分进行系统的分离，研究该类成分的抗肿瘤活性、作用机制及构效关系，为发现高效、低毒的抗肿瘤新药先导化合物提供理论依据和实验基础。

本项目在前期研究工作基础上，进一步对川山橙中单萜吲哚类生物碱进行系统分离和结构鉴定，构建了生物碱化合物库，并研究其抗肿瘤的作用机制和构效关系。从川山橙的枝叶中共分离鉴定了76个生物碱化合物，其中35个为新化合物，29个化合物为首次从该植物中分离得到。系统考察了不同结构类型的单萜吲哚生物碱体外抗肿瘤活性的差异，发现3种白坚木类生物碱对人肝癌细胞株HepG2具有较好的体外抗肿瘤活性，其IC50优于或相当于阳性对照顺铂。采用蛋白质组学方法初步寻找了抗肿瘤作用的靶点蛋白为剪切活化凋亡蛋白caspase-9，caspase-3和PARP。以上研究结果揭示了川山橙中的单萜吲哚类生物碱抗肿瘤的作用机制和构效关系，为寻找和开发出新的抗肿瘤植物药提供科学依据。