Biphenyl-Type Neolignan Derivatives from the Twigs of Magnolia denudata and Their Anti-Inflammatory Activity.

Two new biphenyl-type neolignan derivatives, 2-[2-(hydroxymethyl)-1-benzofuran-5-yl]-4-(prop-2-en-1-yl)phenol (1) and 2'-ethoxy-5,5'-di(prop-2-en-1-yl)biphenyl-2-ol (2), were isolated from the twigs of Magnolia denudata, together with six known compounds (3-8). The structures of 1 and 2 were determined through extensive 1D- and 2D-NMR and mass-spectrometric analyses. Magnolol (6) and honokiol (7) exhibited potent inhibition (IC50 values=4.4±0.2 and 0.71±0.13 μg/ml, resp.) of O$\rm{{_{2}^{{^\cdot} -}}}$ generation by human nutrophils in response to N-formyl-L-methionyl-L-leucyl-L-phenylalanine/cytochalasin B (fMLP/CB). In addition, 2-[2-(hydroxymethyl)-1-benzofuran-5-yl]-4-(prop-2-en-1-yl)phenol (1), 2'-ethoxy-5,5'-di(prop-2-en-1-yl)biphenyl-2-ol (2), magnolol (6), and vanillic acid (8) inhibited fMLP/CB-induced elastase release with IC50 values=6.4±1.5, 2.4±0.4, 1.5±0.2, and 4.8±0.5 μg/ml, respectively.