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.