Grifolin derivatives from Rhododendron dauricum L. and their anti-inflammatory effects.

Rhododendron dauricum L. belongs to the genus Rhododendron within the Ericaceae family. Traditionally, its branches, leaves, and flowers have been utilized in the treatment of bronchitis, cancer, and bacterial infections. In this study, four previously undescribed grifolin derivatives (1-4) and two known analogues (5-6) were isolated from the twigs and leaves of R. dauricum. On the basis of chemical evidence and spectral data analysis (UV, Optical rotation data, 1D/2D-NMR, and HR-ESI-MS), the structures of new compounds were elucidated. Furthermore, all isolated compounds underwent evaluation for their anti-inflammatory properties. The results underscore that compounds 2 and 4 exhibited the potent inhibitory activity on NO production, with IC50 18.86 ± 4.79 μM and 24.59 ± 3.15 μM, respectively. This research contributes to expanding the understanding of the chemical diversity of R. dauricum., offering essential insights for future studies.