基于mTOR通路研究知母皂苷抗肿瘤药效物质基础及作用机制

Anemarrhena asphodeloides Bge. is one of the most popular herbal traditional medicine commonly known as "Zhi-mu" in Chinese, which is widely used in clinical practice to purge fire heat, and nourish dryness in China, Japan, Korea and some Occident. “Zhi-mu” has a broad range of pharmacological effects such as anti-tumor, anti-aging, immune-strengthening, and hypoglycemic effect, among them anti-tumor activity has attracted much attention over the years. However, the effective components and the mechanism of anti-tumor are not clear. In view of the herb’s extract and the crude steroidal saponins’ anti-tumor effect, this programme is designed to systemically study the chemical constituents of the rhizomes of Anemarrhena asphodeloides Bge., mainly steroidal saponins. The anti-tumor mechanisms focus on induction of apoptosis, cell cycle arrest and inhibition of angiogenesis, metastasis through mTOR cell signal. Moreover, based on relative work about chemical components and pharmacological competence of the herb, the programme is also aimed at identifying SAR of these components, finding out regular patterns of the steroid aglycone influencing anti-tumor activity. The result of the plan will provide not only academic guidance to the usage of "Zhi-mu", but also a reference for those who are looking for anti-tumor natural medicines. And the research will lay a good basis for the development of new drug which has independence intellectual property rights of our country.

中药知母功效清热泻火、生津润燥，具有抗衰、增强免疫、降血糖及抗肿瘤等作用，临床应用广泛，近年来其防癌抗癌活性备受关注，但药效物质基础及作用机制尚不明晰，制约着知母在抗癌方面的应用。本项目由前期研究基础出发，对知母中具抗肿瘤活性的甾体皂苷类成分进行系统的化学成分研究，通过体外、体内抗肿瘤活性及mTOR信号通路筛选来明确其抗肿瘤药效物质基础；并基于该类化合物对mTOR信号通路的作用，重点研究对自噬、细胞凋亡、肿瘤血管形成、肿瘤细胞侵袭和转移的影响，同时结合其他甾体皂苷的研究成果，阐明该类型化合物发挥抗肿瘤作用的确切机制，扩展和深化知母抗癌作用研究；最后通过分析知母甾体皂苷及类似化合物抗肿瘤作用的构效关系，指导甾体皂苷在抗肿瘤药效方面的定向修饰、合成，探寻从中药中发现新的抗肿瘤药物。本项目为阐明知母抗癌疗效的药效物质基础、明确作用机制均具有重要意义，也会有力推动中医抗癌理论发展。

知母为清热泻火类常用中药，具有抗衰、降血糖、增强免疫及抗癌等方面作用，近年其抗癌方面活性研究开展较为广泛。本项目在前期研究的基础上，对知母药效物质基础和抗肿瘤作用机制进行研究，主要包括以下四个方面：（1） 对知母药材中化学成分，特别是甾体皂苷类成分进行系统分离、纯化，共鉴定45个化合物，其中甾体皂苷类23个，新化合物8个，对药材中多糖成分进行分离纯化，获得2个多糖，为后继的药理筛选及机制深入研究提供相应物质基础，新发现抗肿瘤活性好化合物3个；（2） 对知母中主要甾体皂苷母核薯蓣皂苷元及菝葜皂苷元进行结构修饰，寻找新的抗肿瘤活性成分，其中薯蓣皂苷元经修饰获得44个化合物，其中B3和C1等化合物抗肿瘤活性良好，正深入研究其作用机制；（3）在通过MTT法筛选上述化合物抗肿瘤活性的基础上，深入研究甾体皂苷类成分特别是timosaponin AIII对mTOR通路抗肿瘤药理作用机制，发现其在抑制新生血管形成和诱导肿瘤细胞周期阻滞过程中发挥重要的作用；（4）对知母药材中含量虽然高、但抗肿瘤活性弱的成分timosaponin BIII进行酸水解，研究其在炮制、体内可能存在的转化规律，发现其可在酸性条件下可转化成抗肿瘤活性好的化合物，揭示了知母药材中不仅仅存在具有抗肿瘤活性的成分，也有在炮制、体内转化过程存在结构相互转化而形成新的抗肿瘤活性化合物，增强药材整体活性。上述研究成果为知母成分抗肿瘤药效物质基础、作用机制、创新中药研发及指导临床合理用药提供重要的科学依据。