羊踯躅（Rhododendron molle）又称黄杜鹃、闹羊花等，为杜鹃花科杜鹃花属植物。羊踯躅是落叶灌木，高0.5-2米，羊踯躅可治疗风湿性关节炎、跌打损伤。其分布于江苏、安徽、浙江、江西、福建、河南、湖北、湖南、广东、广西、四川、贵州和云南。羊踯躅的花、果实和根等部位含有马醉木毒素、闹羊花毒素、和andromedotoxin等成分，误食令人呕吐、腹泻或痉挛。医药上羊踯躅被用于麻醉剂和镇痛药，全株可做农药。本课题组前期对于羊踯躅的研究发现该植物中的二萜及其苷类成分具有较强的镇痛作用，可能是其发挥镇痛作用的主要药效物质之一。然而，对于该植物中含有的大量的三萜类成分，缺乏系统研究。杜鹃花科植物中的三萜类成分具有高度氧化、裂解等独特的结构特点，前期研究发现羊踯躅根三萜部位具有抗炎、镇痛等生物活性，因此本论文针对该植物所含有的三萜类成分进行分离并获取新颖结构的三萜类化合物，试图进一步揭示该植物的药用物质基础。

本研究通过用石油醚、二氯甲烷、乙酸乙酯和甲醇经索氏提取得到四个不同的部位，经过HPLC-MS分析发现三萜类化合物主要存在于二氯甲烷和乙酸乙酯部位。对这两个部位中的三萜类成分进行针对性的分离，共得到了65个三萜类化合物，综合运用多种波谱技术（UV、IR、HRESIMS、NMR等）鉴定了这些化合物的平面结构。通过偶合常数、NOESY以及单晶X-ray衍射实验确定化合物的立体结构。其中，新化合物有15个 (1-6, 23-31)，化合物23是降1个碳原子的5/6/6/6/6环系的三萜化合物；化合物4、5、26、31均是A环氧化后C2与C23形成七元内酯环，产生7/6/6/6/6环系的新三萜；化合物1、24、27均是A环裂环的降1个碳的6/6/6/6环系化合物；化合物3、25是A环裂环的降3个碳化合物，化合物2, 28是A环裂环C2成甲酯的降1个碳的6/6/6/6环系化合物；化合物6为新的被氧化的齐墩果烷型三萜，29、30是新的被氧化的乌苏烷型三萜。

课题组前期筛选发现羊踯躅具有GABA_A受体调节作用。GABA_A受体调节药物可作为麻醉止痛剂，或用于治疗焦虑，癫痫，睡眠障碍，精神障碍等疾病。为了发现新的具有麻醉镇静止痛作用的活性先导化合物以及进一步阐明羊踯躅的传统功效与化学成分的相关性，对分离得到的单体化合物进行体外活性筛选。GABA_A受体有多个亚型，其中α₁β₂γ₂亚型为大脑中最主要的亚型。FLIPR膜电位检测实验，结果显示，化合物4，5，6，26，31具有α₁β₂γ₂亚型GABA_A受体的正性调节作用。采用LPS诱导小鼠腹腔巨噬细胞TNF-α生成模型进行抗炎活性筛选，结果显示化合物18，25和47具有中等强度的抗炎活性。

研究结果显示，羊踯躅中的部分三萜类成分化合物具有α₁β₂γ₂亚型GABA_A受体的正性调节作用和抗炎作用，与羊踯躅麻醉和镇痛的传统功效一致，为更加全面揭示羊踯躅的功效物质和先导物的发现提供了重要线索。

Rhododendron molle, also known as Huang Dujuan, Nao Yanghua, is a plant in Rhododendron species of rhododendraceae. Rhododendron molle is a deciduous shrub and grows in 0.5-2 meters high. Rhododendron molle can treat rheumatoid arthritis and bruise injury. They are distributed in Jiangsu, Anhui, Zhejiang, Jiangxi, Fujian, Henan, Hubei, Hunan, Guangdong, Guangxi, Sichuan, Guizhou and Yunnan provinces. Total plant, including flowers, fruits, roots and other parts, contains intoxication toxin, naoyanghua toxin, and andromedotoxin and other components, which make people vomit, diarrhea or spasm when eaten by mistake. Sheep often linger and die after eating, so it was named “Yang Zhizhu”. In medicine, Rhododendron molle is used as anesthetics and analgesics, and the whole plant can be used as pesticide. Early studies on the plant have reported that diterpenoids and their glycosides showing certain analgesic effect, which may be the active component of the plant’s efficacy. However, the triterpenoids in this plant have not been systematically studied. Therefore, based on the full literature research on the active components of rhododendron family, in this paper, the triterpenoids contained in Rhododendron molle roots are separated and the new skeleton triterpenoids are obtained, trying to reveal the medicinal material basis of this plant.

In this study, four different parts were extracted by petroleum ether, dichloromethane, ethyl acetate and methanol. Triterpenoids were found in dichloromethane and ethyl acetate according to the test of mass spectrometry. A total of 65 triterpenoids were isolated from these two parts, and their plane structures were established on the basis of a variety of spectrum analysis (UV, IR, HRESIMS, NMR, etc.), The stereoscopic structures of the compounds were determined by coupling constant, NOESY and single crystal X-ray diffraction. The results show that there are 17 new compounds, of which compound 23 is a new skeleton triterpenoid. Compound 23 forms a new skeleton triterpenoid of 5/5/6/6/6/6-fused ring system through the process of A-ring cleavage, elimination of C-23, rearrangement of C2 and C4, esterification of C3 and C24; Compounds 4, 5, 26 and 31 are all 7-membered lactone rings formed by C2 and C23 after A-ring oxidation, resulting in new triterpenoids of 7/6/6/6-ring system; compounds 1, 24 and 27 are 6/6/6/6-ring compounds of 1-carbon reduction of A-ring cleavage ring; compounds 3 and 25 are compounds of 3-carbon reduction of A-ring cleavage ring, compound 2 and 28 are 6/6/6/6-ring compound with one carbon reduction from C-2 to methyl ester; compound 6 is a new oxidized oleanolane triterpene, 29 and 30 are new oxidized Ursane-type triterpenes.

       GABA_A receptor modulators can be used as anesthetics, or in the treatment of anxiety, epilepsy, sleep disorders, mental disorders and other diseases. There are many subtypes of GABA_A receptor, among which α₁β₂γ₂ subtype is the most important subtype. The results showed that compounds 2，5，14, 33 amd 45 had a positive regulatory effect on α₁β₂γ₂ subtype GABA_A receptor.

It was found that Rhododendron molle has the regulatory effect of GABA_A receptor. GABAA receptor modulators can be used as anesthetics and analgesics, or in the treatment of anxiety, epilepsy, sleep disorders, mental disorders and other diseases. In order to find a new active leading compound with analgesic effect and to further clarify the correlation between the traditional efficacy of Rhododendron molle and its chemical components, the isolated monomers were screened for in vitro activity. There are many subtypes of GABA_A receptor, among which α₁β₂γ₂ subtype is the most important subtype. The results showed that compound 2，5，14，33 and 45 had a positive regulatory effect on GABA_A receptor of α₁β₂γ₂ subtype. The anti-inflammatory activity of compounds 18, 19 and 47 was screened by LPS induced TNF - α production model of mouse peritoneal macrophages.

The results showed that some triterpenoids in Rhododendron molle had positive regulatory effects on GABA_A receptor of α₁β₂γ₂ subtype and anti-inflammatory effects, which was consistent with the traditional effects of anesthesia and analgesia of Rhododendron molle, and provided an important clue for the discovery of more comprehensive effective substances and precursors of Rhododendron molle.