| Abstract: | In the present study, nine new cembrane-type diterpenoids, namely ximaonanolobatins A—I (1—9), together with six related known analogs (10—15) and four known tetraprenylated alkaloids malonganenones D, E, H, and K (16—19) were isolated from the soft coral Sinularia nanolobata collected off the Ximao Island in the South China Sea. The structures of 1—9 were robustly established by a combination of detailed spectroscopic analyses, chemical reactions, quantum mechanical (QM)-NMR methods, biogenetic consideration, and the comparison with those literature data. The absolute configuration of 1 was confirmed by X-ray diffraction analysis, and the absolute configuration of 2 was determined by QM-NMR calculations and chemical transformation. In addition, the absolute configuration of 3 was determined using the modified Mosher's method. All these isolates were evaluated for their anti-inflammatory and anti-tumor activities. The results showed that only compound 15 exhibited potential anti-inflammatory effect against LPS-induced TNF-α release in RAW264.7 macrophages with an IC50 value of 12.6 μmol/L.  |
