特色民族药鞣质成分体内活性化产物的结构和活性研究

Tibetan, Mongolian, and Uygur medicinal systems frequently use tannin-rich medicinal herbs, such as the fruits of Terminalia chebula Retz, which is the most frequently used herbal drug in ethnic medicinal prescription and contains high amounts of hydrolyzable tannins. Other common ethnomedicinal and food materials, such as the woods of Xanthoceras sorbifolia Bunge and the stems of Cynomorium songaricum Rupr, harbor many condensed tannins with A- and B-type flavanol linkages, respectively. With their complex structures being solved gradually, the therapeutic effects of tannins are attracting more attention. For example, 2 small molecular tannins have been approved by the FDA as botanical drugs in recent years: Veregen (green tea catechins) and Fulyzaq (the oligomeric proanthocyanidin from Croton lechleri). Previous studies have shown that Cynomorium tannins are degraded easily by cysteine to form small molecular flavanol-cysteine conjugates that have increased inhibition against α-glucosidase. After administration of the wood powder of Xanthoceras sorbifolia, the large molecular tannins that were nonextractable by solvents were degraded into bioactive small molecules in vivo. However, the structures and bioactivities of many other compounds that are produced through biotransformation or conjugation with other molecules (bio-activation products) in vivo are unknown. This project intends to investigate the structures and bioactivities of the tannin bio-activation products in serum, after X. sorbifolia wood and C. songaricum stems have been administered in their traditional powder forms. This research will increase our understanding of ethnomedicines and guide the discovery of new drugs that are based on natural medicines.

藏、蒙、维等民族用药中常富含鞣质，如民族药复方中出现频率最高的诃子含有大量可水解鞣质，特色民族药材文冠木和锁阳则含有大量缩合鞣质(分别为黄烷醇以A-和B-型连接的聚合物)。随着其复杂结构的解明，鞣质类的药效也日益受到重视。近年美国FDA通过的两个植物组分药均为小分子鞣质(绿茶的儿茶素组分Veregen和秘鲁巴豆的黄烷醇低聚体Fulyzaq)。前期研究显示锁阳鞣质易被半胱氨酸降解，生成的小分子黄烷-半胱氨酸加成物对α-葡萄糖苷酶的抑制活性更强；文冠木粉末给药后，不能被溶剂提取的大分子鞣质在体内降解为活性小分子。然而，鞣质的体内转化物尚有大量结构和活性没有解明。本课题拟以文冠木及锁阳为例，按民族用药习惯粉末给药后，研究血清中鞣质的代谢及与其他物质结合后的生物活性产物（代谢活性化产物）。确定这些代谢活性化产物的化学结构和生物活性，为展现民族医药科学精髓和基于民族药的新药发现提供科学数据。

藏、蒙、维等民族医常用富含鞣质的药材，民族药复方最常用的诃子主要含可水解鞣质，特色蒙药材文冠木、锁阳则含有大量缩合鞣质（黄烷醇聚合物，也称作原花青素）。本项目研究了鞣质体内代谢及与其他物质结合的生物活性产物（代谢活性化产物），确定这些代谢活性化产物的化学结构和生物活性。分离鉴定出文冠木鞣质为主在体内产生的4种代谢物。发现文冠木喂食奶羊后，含这些代谢物及文冠木原成分的羊乳能促进肝脏和胰腺发育。分析检测到锁阳在体内吸收和转化的黄烷醇成分：儿茶素、表儿茶素、原花青素A1（A1）、原花青素A2（A2）和原花青素B1（B1）。发现除了表儿茶素外，A2是锁阳黄烷醇聚合物的延伸单元，锁阳黄烷醇聚合物在体内释放出表儿茶素和A2。B1可在体内转化成A1。被体内吸收及转化的黄烷醇有抗氧化和抗炎活性，其中二聚体比单倍体活性更好。与喂食锁阳的奶羊羊奶中浓度相比，纯品黄烷醇需更高浓度才显示抗炎活性，提示锁阳在体内吸收的多种成分及代谢物有相加或协同作用。发现，A2可进入L02人正常肝细胞并保护细胞免受叔丁基过氧化氢氧化损伤，其作用机理与激活Nrf2有关。制备了A1-丙酮（10）和A2-半胱氨酸（11）缩合物，10和11可清除自由基，10还显著抑制α-葡萄糖苷酶活性，提示有潜在的抗糖尿病作用。发现诃子鞣质主要单元没食子酸及类似物莽草酸在诃子与麻黄同时灌胃大鼠时，生成新的麻黄碱-没食子酸（12）及麻黄碱-莽草酸（13）结合物，灌胃大鼠诃子和麻黄粉末0.5小时后，12和13达到最大血药浓度。斑马鱼实验中，12和13可降低硫代乙酰胺引起的活性氧升高，显著增加谷胱甘肽水平。发现鞣花酸、黄烷醇及一些类似多酚成分在斑马鱼模型中有抗血栓作用。上述研究结果为展现民族医药科学性和基于民族药的新药发现提供了数据。