Five new meroterpenoids from Rhododendron anthopogonoides and their anti-inflammatory activity

Five meroterpenoids, rhodonoids K-M (1-2), daurichromene E (3), and grifolins A-B (4-5), together with seven known compounds (6-12), were isolated from Rhododendron anthopogonoides. The chemical structures were established through comprehensive HRESIMS, UV, IR, and NMR data analysis, and their absolute configurations were determined by comparing their experimental electronic circular dichroism (ECD) with computed values. Compounds 1 and 3 exhibited significant inhibitory effects on LPS-induced inflammation in RAW264.7 cells. They notably suppressed the mRNA expression of inflammatory factors such as IL-1β, IL-6, and TNF-α, and also down-regulated the protein expression of iNOS and COX-2.