Ulapualides C-E Isolated from a Hawaiian Hexabranchus sanguineus Egg Mass

Three new ulapualides (3-5) were isolated from egg masses of the nudibranch Hexabranchus sanguineus. The structures of 3-5 were deduced by analyses of physical and spectroscopic data in comparisons with ulapualides A (1) and B (2). Ulapualide C demonstrated submicromolar cytotoxicity against select NCI cell lines (768-0, DU-145, MDA-MB-231, and A549) with the most potent activity against MDA-MB-231 cells (IC₅₀ 0.58 μM). Ulapualides A (1) and B (2) were 2- to 4-fold more potent than 3.