Two new flavonoids, (2S)-6,8-dimethyl-5,7,3',4'-tetrahydroxyflavanone 4'-O-β-D-glucopyranoside (1) and quercetin 3-O-β-D-(6''-p-methoxybenzoyl)-galactopyranoside (2), together with ten known flavonoids (3-12) were isolated from the leaves of Rhododendron dauricum L. The structures of the flavonoids were characterized from spectroscopic data (1D and 2D NMR and HR-ESI-MS). The isolated flavonoids were evaluated for their inhibitory effects on the production of tumour necrosis factor (TNF)-α in LPS-stimulated RAW 264.7 cells. Compound 11 exhibited inhibitory activity against TNF-α production with an IC50 value of 46.2 ± 1.2 µM.
Keywords: Ericaceae; Rhododendron dauricum; TNF-α; flavonoid.