||In the continuing search for novel substances from marine invertebrates originally distributed in Taiwan waters. The octocoral Briareum excavatum was transplanted to the culturing tanks located in the NMMBA for its interesting chemical constituents. This study had led to the isolation of 32 briarane derivatives 1–32, including 18 new compounds,|
briaexcavatins I–Z (1–18) from the cultured B. excavatum. The structures of compounds
1–32 were determined by spectroscopic methods and the structures of briaexcavatins I (1), U (13), W (15) and the known compound excavatolides C (19) and E (20) were confirmed by X-ray data analysis. The absolute configurations of briaranes 13 and 20 were determined by X-ray diffraction analysis and modified Mosher’s method, respectively. It is noteworthy
to mention that briaexcavatin Y (17) represents the first example of a briarane possessing a C-8/9 epoxy group. The relationships between 13C NMR chemical shifts and the conformations of the briaranes possessing an 11,12-epoxy group are described.
In biological activity experiments, briaranes 11, 19, and 24 exhibited weak cytotoxicity toward CCRF-CEM tumor cells and compounds 2 and 19 showed weak
cytotoxicity toward DLD-1 tumor cells, respectively. Moreover some of these briaranes such as compounds 24, 26, and 27 have displayed mild inhibitory effects on superoxide anion generation by human neutrophils. Compounds 14, 24, 26, and 30 showed mild inhibitory effects on human neutrophil elastase release. Compound 18 exhibited mild
activity to enhance human neutrophil elastase release.