Six new guaiane dimers, xyloplains A-F (1-6), with connecting patterns through two direct C-C bonds (C-1 to C-3', C-2 to C-1'), were isolated from the roots of Xylopia vielana. Their structures were elucidated clearly using extensive analysis of 1D NMR and 2D NMR, combined with Cu-Kα X-ray diffraction and circular dichroism (CD) experiments. In additon, all of the isolates were tested for anti-inflammatory activity by measuring the amount of nitric oxide produced. To our delight, compounds 2 and 6 exhibited moderate inhibitory activity against the production of nitric oxide with IC50 value of 34.5 and 31.1 μM, respectively, in RAW264.7 cells stimulated by LPS.
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