Chemical Constituents from Soft Coral Clavularia spp. Demonstrate Antiproliferative Effects on Oral Cancer Cells.

Five new eudensamane-type sesquiterpene lactones, clasamanes A-E ( 1 - 5 ), three new dolabellane-type diterpenes, clabellanes A-C ( 6 - 8 ), and fifteen known compounds ( 9 - 23 ) were isolated from the ethanolic extract of Taiwanese soft coral Clavularia spp. The structures of all undescribed components ( 1 - 8 ) were determined by analysis of IR, mass, NMR, and UV spectroscopic data. The absolute configuration of new compounds was determined by using circular dichroism and DP4+ calculations. The cytotoxic activities of all isolated marine natural products were evaluated. Compound 7 showed a significant cytotoxic effect against oral cancer cell line (Ca9-22) with an IC 50 value of 7.26 ± 0.17 μg/mL.