Two novel flavonoids from the leaves of <i>Rhododendron dauricum</i> L. with their inhibition of TNF-α production in LPS-induced RAW 264.7 cells

Abstract

Two new flavonoids, (2<i>S</i>)-6,8-dimethyl-5,7,3',4'-tetrahydroxyflavanone 4'-O-<i>β</i>-D-glucopyranoside (<b>1</b>) and quercetin 3-O-<i>β</i>-D-(6''-<i>p</i>-methoxybenzoyl)-galactopyranoside (<b>2</b>), together with ten known flavonoids (<b>3</b>-<b>12</b>) were isolated from the leaves of <i>Rhododendron dauricum</i> 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 <b>11</b> exhibited inhibitory activity against TNF-α production with an IC₅₀ value of 46.2 ± 1.2 µM.