Biflavonoids and bi- and tricoumarins from Daphne mezereum and inhibition of TNF-α secretion.

Daphne mezereum L. (Thymelaeaceae) was an important medicinal plant in Norway during the 18^th and 19^th centuries and used against diseases such as diarrhea, swelling, stomach pain, and tuberculosis. Five previously undescribed phenolic compounds, including two biflavonoids with a catechin core structure, two tricoumarins, and one bicoumarin, together with ten known compounds were isolated from a 50% EtOH extract of the bark of D. mezereum. Using NMR, HRESIMS, acid hydrolysis, and circular dichroism spectra, the biflavonoids were identified as 3'-hydroxygenkwanol A and 3'-hydroxydihydrodaphnodorin B, and the coumarins were identified as 3'''-O-acetyltriumbellin, triumbellin 4'''-O-β-D-glucopyranoside, and daphnogitin-7-O-β-D-glucopyranoside. The absolute configuration of dihydrodaphnodorin B was for the first time established as 2R, 3S, 2''S, 3''S. Daphnin, syringin, 3'-hydroxydihydrodaphnodorin B, dihydrodaphnodorin B, and neochamaejasmin A and B were identified as the major secondary metabolites in the extract. Neochamaejasmin A and B showed the most potent inhibition of TNF-α secretion in Con A stimulated peripheral blood mononuclear cells (PBMCs) with 71.3 ± 3.4 and 83.5 ± 11.5% inhibition, respectively, at 50 μM.