Highly Oxygenated Dimeric Grayanane Diterpenoids as Analgesics: <scp>TRPV1</scp> and <scp>TRPA1</scp> Dual Antagonists from <i>Rhododendron molle</i>
Lang Huang, Guijuan Zheng, Yuanyuan Feng, Pengfei Jin, Biao Gao, Hanqi Zhang, Xiaomin Ma, Junfei Zhou, Guangmin Yao
Abstract
Comprehensive Summary Six highly oxygenated dimeric grayanane diterpenoids (1—6) including three new ones, bismollethers A—C (1—3), were isolated from the flowers of Rhododendron molle collected at Qichun, Hubei, China. The structures and relative configurations of 1—6 were determined by comprehensive spectroscopic data analysis and 13 C NMR calculation with DP4+ analysis. The absolute configurations of bismollethers A—C (1—3) and birhodomollein B (5) were indubitably assigned by single‐crystal X‐ray diffraction analysis, revealing the head‐to‐tail linking manner of diterpenoid monomers. Bismollether A (1) is a caged dimeric grayanane diterpenoid linked through two oxygen‐bridges of C‐2 − O − C‐14′ and C‐14 − O − C‐2′, featuring a unique 1,8‐dioxacyclotetradecane motif. The plausible biosynthesis pathways of 1—6 are proposed. All the isolates displayed significant analgesic activities and their structure‐activity relationships were discussed. Grayanane diterpenoid dimers were found to be TRPV1 and TRPA1 dual antagonists, and docking studies provide a structural basis to design potent analgesics.