Isolaurenidificin and Bromlaurenidificin, Two New C 15 -Acetogenins from the Red Alga Laurencia obtusa.

Chromatographic fractionation of the CH₂Cl₂/MeOH extract of the Red Sea red alga Laurencia obtusa gave two new hexahydrofuro[3,2- b ]furan-based C15 -acetogenins, namely, isolaurenidificin ( 1 ) and bromlaurenidificin ( 2 ). The chemical structures were elucidated based on extensive analyses of their spectral data. Compounds 1 and 2 showed no toxicity ( LC 50 > 12 mM) using Artemia salina as test organism. Both compounds showed weak cytotoxicity against A549, HepG-2, HCT116, MCF-7, and PC-3 cells, however, they exhibited a relatively potent cytotoxic activity against peripheral blood neutrophils. This can be attributed partly to induction of apoptosis.