Nine previously undescribed diterpene glucosides, rhodomicranosides A-I, comprising leucothane, 4,5-seco-ent-kaurane, and grayanane types, respectively, were isolated from the leaves of Rhododendron micranthum, along with seven known diterpenoids. Their structures were elucidated based on extensive spectroscopic analyses such as HRESIMS, 1D and 2D NMR, UV, and IR, and their absolute configurations were determined by various methods including X-ray diffraction analysis, electronic circular dichroism spectroscopy (ECD), calculated ECD, and Mo2(OAc)4-induced ECD, as well as chemical methods. This is the first time to report the crystal structures of leucothane diterpene glycosides. Rhodomicranosides A-C represent the first examples of 15α-hydroxy-leucothane diterpenoids, leucothane diterpene diglucosides, and 9β-hydroxy-leucothane diterpenoids, respectively. Rhodomicranosides D and E are the second and third examples of 4,5-seco-ent-kaurane diterpenoids, and this is the first time to report 4,5-seco-ent-kaurane-type diterpenoids from the genus of Rhododendron. Rhodomicranosides F and G are the first examples of 5α-H-grayan-1(10),9(11)-diene-6-one diterpenoids. Some isolated diterpenoids were evaluated for their analgesic activity in an acetic acid-induced writhing test, and rhodomicranosides A-E and H, pierisformoside F, iso-grayanotoxin II, and grayanotoxins I, III, and IV showed significant analgesic effects with the percentage inhibitions over 50% at the dose of 1.0 mg/kg. In particular, grayanotoxins I and III exhibited more potent analgesic activity than morphine at a dose of 0.2 mg/kg, and they showed significant analgesic activity even at a lower dose of 0.04 mg/kg with the inhibition rates of 71.5% and 69.3%, respectively. Their preliminary structure-activity relationships were discussed.

中文翻译：

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Rhodomicranosides A-I，具有不同碳骨架的镇痛二萜糖苷来自小红杜鹃

九种以前未描述的二萜糖苷、红微核苷 AI，分别包含白光烷、4,5-seco-ent-kaurane 和grayanane 类型，从红杜鹃的叶子中分离出来，以及七种已知的二萜。它们的结构是基于广泛的光谱分析（如 HRESIMS、1D 和 2D NMR、UV 和 IR）阐明的，并且它们的绝对构型通过各种方法确定，包括 X 射线衍射分析、电子圆二色光谱 (ECD)、计算 ECD、和 Mo2(OAc)4 诱导的 ECD，以及化学方法。这是首次报道白光烷二萜糖苷的晶体结构。Rhodomicranosides AC 代表 15α-羟基-白烷二萜、白烷二萜二糖苷和 9β-羟基-白烷二萜的第一个例子，分别。Rhodomicranosides D 和 E 是 4,5-seco-ent-kaurane 二萜类化合物的第二个和第三个实例，这是首次报道来自杜鹃花属的 4,5-seco-ent-kaurane-type 二萜。Rhodomicranosides F 和 G 是 5α-H-grayan-1(10),9(11)-diene-6-one 二萜的第一个例子。在醋酸诱导的扭体试验中评估了一些分离的二萜类化合物的镇痛活性，并且红小花苷 AE 和 H、梨花苷 F、异灰霉毒素 II 和灰霉毒素 I、III 和 IV 显示出显着的镇痛作用，抑制百分比超过 50 % 剂量为 1.0 mg/kg。特别是，灰毒素 I 和 III 在 0.2 mg/kg 的剂量下表现出比吗啡更强的镇痛活性，即使在 0.0 的较低剂量下，它们也显示出显着的镇痛活性。04 mg/kg 的抑制率分别为 71.5% 和 69.3%。讨论了它们的初步构效关系。