具有镇痛抗炎活性的柠檬苦素类化合物的结构改造及构效关系研究

Limonin is highly oxygenated triterpenoids, abundant in citrus fruit and other plants found in the Rutaceae and Meliaceae family plants. Limonin exhibit a wide range of biological activities, including analgesic, anti-inflammatory and antitumor. However, limonin present poor water-solubility and low bioavailability (3%-14.5%), which greatly limit its clinical application. Based on the analysis of the structural characteristics of limonin, we modified its structure by introducing various tertiary amine moieties onto C (7)-position of limonin to yield nitrogen-containing derivatives with high solubility in water. After pharmacological screening, XY-130322 was obtained as a analgesic and anti-inflammatory candidate compounds, its analgesic activity is more potent than that of aspirin, and its anti-inflammatory activity is stronger than that of naproxen. In addition, the oral bioavailability of XY-130322 was 82.6%, which implied its good druggability. In this study, limonin was selected as the lead compound, and it's structure of A, B and D rings will be modified by means of ring opening, ring expansion and aza, etc. and thus convert limonin from triterpenoids into terpene alkaloids. A total of 90 limonin derivatives are designed and synthesized, and after analgesic, anti-inflammatory screening and pharmacokinetic studies, we expect to obtain one or two novel analgesic and anti-inflammatory candidate compounds with high potency, low toxicity, good oral absorption, and independent intellectual property rights. Meanwhile, the investigation of the mechanism for the candidate compounds may provide new ideas and theory basis in further structural modification of limonoids.

柠檬苦素广泛存在于柑橘类植物中，为高度氧化的四环三萜类化合物，具有镇痛、抗炎、抗肿瘤等活性，安全性好。但柠檬苦素的水溶性低，口服吸收差，生物利用度只有3%~14.5%，影响了其临床应用。本课题组在分析柠檬苦素结构特点的基础上，将其7位羰基成酮肟后再醚化，引入叔胺基团，得到水溶性较好的柠檬苦素类似物，发现了镇痛活性明显强于阿司匹林、抗炎活性强于萘普生的化合物XY-130322，其口服生物利用度达82.6%，显示出良好的成药性。本课题以柠檬苦素为先导化合物，采用开环、扩环、氮杂等手段，对柠檬苦素的A环、B环和D环进行结构改造，通过引入氮原子，将三萜类柠檬苦素转化为萜类生物碱，设计并合成90个类似物，通过镇痛、抗炎筛选和药代动力学研究，期望发现1至2个活性强、毒副作用低、口服吸收好、具有自主知识产权的新型镇痛抗炎候选化合物，并探索其作用机理，为柠檬苦素类化合物的进一步结构改造提供思路和理论依据。

柠檬苦素广泛存在于柑橘类植物中，为高度氧化的四环三萜类化合物，具有镇痛、抗炎、抗肿瘤等活性，安全性好。但柠檬苦素的水溶性低，口服生物利用度只有3%~14.5%，影响了其临床应用。.本项目在分析柠檬苦素结构特点的基础上，首先将柠檬苦素分子中的氧桥脱去后形成双键，得到脱氧柠檬苦素，再分别对柠檬苦素和脱氧柠檬苦素的A环、B环和呋喃环进行结构改造，设计合成了123个目标化合物。.通过小鼠醋酸扭体模型和小鼠热水甩尾模型评价了目标化合物的镇痛活性，发现化合物I-A-5、II-B-7、II-B-8、III-A-5、IV-A-1和VI-B-9的镇痛活性强于阿司匹林；通过二甲苯致小鼠耳廓肿胀模型和角叉菜胶足肿胀实验评价了化合物的抗炎活性，发现化合物I-A-5、II-A-7、VI-A-5、VII-A-5和VII-A-6的抗炎活性强于萘普生；对候选化合物进行了初步的药代动力学评价，发现化合物VI-A-5具有较好的口服生物利用度（86.3%）；选择化合物VI-A-5和VII-A-6进行了抗类风湿性关节炎实验，发现VI-A-5高剂量组的大鼠关节炎指数评分与阳性药托法替尼相当；选择部分化合物进行了急性毒性和hERG毒性评价，发现化合物VI-A-5和VII-A-6具有较好的安全性；选择候选化合物I-B-7和VI-A-5进行了初步的作用机制探索，发现化合物VI-A-5可能是通过抑制MAPK信号通路中的关键蛋白，ERK1/2、JNK和p38MAPK的磷酸化而阻止其活性，抑制下游炎性介质的生成，从而发挥抗炎作用。.综上所述，通过本项目的研究，发现了一个候选药物VI-A-5，相关工作获得国家科技重大专项的资助，目前正在进行临床前评价。.在项目完成过程中，已申请发明专利4个，其中2个发明专利已获得授权。已发表SCI论文2篇，另有1篇SCI已经接收，发表国内期刊论文3篇。