Anti-inflammatory cembranoids from the soft corals Sinularia querciformis and Sinularia granosa

Four new cembranoids, querciformolides A-D (1-4), along with two known cembranoids, 7 and 8, have been isolated from the soft coral Sinularia querciformis. Furthermore, chemical investigation of Sinularia granosa has afforded three new cembranoids, querciformolide B (2) and granosolides A (5) and B (6). The structures of the new metabolites were elucidated on the basis of extensive spectroscopic methods, and that of 2 was further confirmed by X-ray diffraction analysis. The absolute configurations of 1 and 2 were determined by a modified Mosher's method. Among these metabolites, 2-6 are rarely found cembranoids possessing a tetrahydrofuran moiety with a 4,7-ether linkage; in addition, 1 is the first epsilon-lactone cembrane found that possesses a tetrahydropyran moiety with a 4,8-ether linkage. None of these compounds were found to be cytotoxic toward a limited panel of cancer cell lines. However, compounds 3, 7, and 8 significantly inhibited the accumulation of the pro-inflammatory iNOS and COX-2 proteins in LPS-stimulated RAW264.7 macrophage cells.