三七中抗癌活性皂苷元的超分子体系构筑及与牛血清蛋白相互作用研究

Ginseng sapogenins is the series of degradation products from Panax Notoginseng, a native medicinal materials produced in Yunnan. Being highly active, natural, non-toxic and easily prepared, it is a promising candidate for anti-cancer drugs. However, poor solubility and bioavailability have limited its application in the pharmaceutical field. Constructing the supramolecular systems of bis-cyclodextrins (bis(CD)s) is an effective way to improve the physico-chemical properties of natural products. But there are no researches on the bis(CD)s complex with ginseng sapogenins. Our previous studies have revealed that bis(β-CD)s can obviously improve the solubility of protopanaxadiol sapogenins by the cooperative binding of two adjacent CD cavities and multiple recognition function. Furthermore, the bis(CD)s can also release protopanaxadiol gradually by competing interactions with bovine serum albumin (BSA) . This study aims to design and synthesize a series of novel bis(β-CD)s and prepare the bis(β-CD)s - ginseng sapogenins supramolecular systems. A series of active supramolecular systems with low toxicity and high solubility and bioavailability will be selected from them. In order to elucidate the multiple recognition mechanism between host and guest, this study will investigate the stability constants and the thermodynamic parameters, and discuss the inclusion mode further. In addition, this study will carry out systematic researches on the mechanism of interaction between ginseng sapogenins or its supramolecular systems with BSA, their binding constants, binding locality and the confirmation changes of BSA as well, which will shed light on the mechanism of the competing interactions of ginseng sapogenins with bis(β-CD)s and BSA at the molecular level. We're particularly interested in exploring the effect of bis(β-CD)s on the interaction of the ginseng sapogenins with BSA. The research will provide an important theoretical basis for the applications of CDs in the solubilization and delivery of natural anti-cancer medicines.

人参皂苷元为滇特产药材三七的系列降解产物，是前景看好的高活性、天然无毒且易制备的抗癌候选药物，但较低水溶性和生物利用度限制其应用。通过桥联环糊精构筑超分子体系是改善天然产物理化性质的一种有效途径，然而未见桥联环糊精包结皂苷元的报道。我们前期研究发现，具有双重疏水作用和多重识别功能的桥联环糊精，可显著提高原人参二醇皂苷元的溶解度，并通过与牛血清蛋白（BSA）竞争包结缓释出原人参二醇。本项目拟设计合成系列新型桥联环糊精，制备合成受体与4种皂苷元的超分子体系，筛选出低毒、较好水溶性和生物利用度的活性超分子体系，测定键合常数和热力学参数，阐明桥联环糊精识别作用机理。并研究皂苷元或超分子体系与BSA的作用机制，结合常数、位点及距离等。旨在分子水平上阐明桥联环糊精和BSA对皂苷元的竞争包结作用机制，并探讨桥联环糊精对皂苷元-BSA相互作用的影响。为环糊精对抗癌天然药物的增溶和传递应用提供重要理论依据。

人参皂苷元为滇特产药材三七的系列降解产物，是前景看好的高活性、天然无毒且易制备的抗癌候选药物，但较低水溶性和生物利用度限制其应用。通过桥联环糊精构筑超分子体系是改善天然产物理化性质的一种有效途径，然而未见桥联环糊精包结皂苷元的报道。我们前期研究基础上，设计与合成了29种单修饰和桥联beta-环糊精，研究这些化合物对原人参三醇（PPT）的包合行为，结果表明主客体之间形成1:1的包合物，桥联环糊精的键合能力都显著强于对应的单修饰环糊精，进一步阐明桥联环糊精的多重识别作用机制和主客体的尺寸匹配关系。并用2D ROESY谱图推测了超分子体系可能的包结模式。制备了29种PPT的超分子体系，用1H NMR、XRD、IR、SEM、XRD等方法表征。溶解度实验表明所合成的主体对PPT都有不同程度的增溶作用，PPT的水溶解度增加49—5933倍。PPT增溶大小顺序与主客体稳定常数大小的顺序一致,桥联环糊精29的增溶效果最好。采过荧光光谱研究了29个PPT超分子体系与BSA的作用机制，发现超分子体系与BSA之间发生的均为静态猝灭，以静电引力为主要的驱动力；且结合位点为1；超分子体系的加入使BSA结构中色氨酸残基发生蓝移或是红移；根据计算所得的超分子体系与BSA之间的结合距离可知，偶极-偶极非辐射能量转移是引起BSA发生荧光猝灭的另外一个原因。由于PPT与BSA间的结合稳定常数远远大于合成主体与PPT的稳定常数，故BSA通过竞争包结，能把PPT从超分子体系中夺取出来进行运送。主体的存在导致PPT与BSA的结合作用力由氢键和范德华力转变为静电引力，而所有的主体对PPT与BSA的结合位点数都无显著地影响。进一步采用分子对接与分子动力学模拟方法进行理论验证，所得结果与实验结论基本吻合。这些数据的积累有助于我们理解几种弱相互作用力对超分子体系形成的贡献，为环糊精对抗肿瘤天然产物的增溶和传递应用提供重要理论依据。