Three Chromene Meroterpenoids With Potential Anti-Inflammatory Activity From Rhododendron anthopogonoides.

Three chromene meroterpenoids (1, 3, and 4), were isolated from Rhododendron anthopogonoides. These meroterpenoids possess a benzo-α-pyran core and a linear terpene side chain. Their chemical structures were established by high-resolution electrospray ionization mass spectrometry and comprehensive spectroscopic analysis. The structures of 2 and 3, C-7'/C-8' double-bond isomers, were confirmed by DP4+ analysis via comparison of experimental and calculated NMR chemical shifts, allowing for the revision of the incorrectly assigned configuration of 2. The stereochemistry of the chiral hydroxyls at C-6', C-7', and C-10' in 4 were determined using Mo2(OAc)4-induced electronic circular dichroism spectra, combined with NMR chemical shift calculations. These compounds exhibited weak inhibitory activity against nitric oxide (NO) production in LPS‑stimulated RAW264.7 cells.