Xyloplains A-F, six new guaiane-type sesquiterpenoid dimers from Xylopia vielana

Abstract

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.

Fig. 1. Chemical structures of compounds 1–6.

Fig. 2. Key HMBC, ¹H–¹H COSY and NOESY correlations of 1.

Fig. 3. X-ray structure of 1.

Fig. 4. CD spectrum of compounds 1–4.

Fig. 5. Key NOESY and ¹H–¹H COSY correlations of 4.

Fig. 6. Key NOESY correlations of 5.

Fig. 7. X-ray structure of 5.

Fig. 8. Key NOESY and ¹H–¹H COSY correlations of 6.

Fig. 9. The dose inhibition curves of nitric oxide produced by compounds 2 and 6. The data were obtained from three independent experiments and expressed as the means ± SEM.