Details

Autor(en) / Beteiligte

• Sun, Na
• Qiu, Yue
• Zhu, Yan
• Liu, Junjun
• Zhang, Hanqi
• Zhang, Qihua
• Zhang, Mengke
• Zheng, Guijuan
• Zhang, Chun
• Yao, Guangmin

Titel

Rhodomicranosides A−I, analgesic diterpene glucosides with diverse carbon skeletons from Rhododendron micranthum

Ist Teil von

• Phytochemistry (Oxford), 2019-02, Vol.158, p.1-12

Ort / Verlag

England: Elsevier Ltd

Erscheinungsjahr

2019

Link zum Volltext

Quelle

Elsevier ScienceDirect Journals Complete

Beschreibungen/Notizen

• 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. Sixteen diterpenoids including nine unreported diterpene glycosides were isolated from Rhododendron micranthum. This is the first time to report the crystal structures of the leucothane diterpene glycosides. Rhodomicranosides A−E and H, pierisformoside F, iso-grayanotoxin II, and grayanotoxins I−IV exhibited significant analgesic activities. [Display omitted] •Sixteen diterpenoids were isolated from the leaves of Rhododendron micranthum.•Nine unreported diterpene glucosides with diverse carbon skeletons were reported.•This is the first report of the crystal structures of leucothane diterpene glycosides.•This is the first report of 5α-H-grayan-1(10),9(11)-diene-6-one diterpenoids.•Twelve diterpenoids showed significant analgesic activity at a dose of 0.1 mg/kg.