Nivalones CF, four new meroterpenoids from Rhododendron nivale.

Four new meroterpenoids, namely nivalones CF (1-4), along with a known meroterpenoid, cannabiorcicyclolic acid (5), were isolated from the branches and leaves of Rhododendron nivale. The chemical structures of compounds 1-4 were elucidated through comprehensive spectroscopic analyses, including NMR, UV-Vis, IR, ECD spectroscopy, as well as HR-ESI-MS. The isolated compounds were evaluated for their anti-inflammatory and neuroprotective properties. The inhibitory activity of compound 5 against lipopolysaccharide (LPS)-induced nitric oxide (NO) production was initially demonstrated, showcasing an IC50 value of 21.1 μM. Additionally, both compounds 2 and 5 displayed a notable effect on the viability of H2O2-damaged SH-SY5Y cells, indicating their significant neuroprotection effects.