Xylopidimers A-E, Five New Guaiane Dimers with Various Carbon Skeletons from the Roots of Xylopia vielana

Five new guaiane dimers, xylopidimers A-E (1-5), were isolated and identified from the roots of Xylopia vielana. The structures of 1-5 were elucidated by spectroscopic analysis and further confirmed by single-crystal X-ray diffraction. On the basis of the results of single-crystal X-ray analysis, 1-5 showed different carbon skeletons. Among these compounds, the unique connecting patterns of 1 and 2 caused significant differences on their carbon skeletons, which have not been reported. Moreover, 3-5 were also three new guaiane dimers. Among these compounds, 4 exhibited potent inhibitory activity against the production of nitric oxide with an IC50 value of 4.59 mu M in RAW264.7 cells stimulated by lipopolysaccharide.