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

Chromatographic fractionation of the CH₂Cl₂/MeOH extract of the Red Sea red alga gave two new hexahydrofuro[3,2-]furan-based C-acetogenins, namely, isolaurenidificin () and bromlaurenidificin (). The chemical structures were elucidated based on extensive analyses of their spectral data. Compounds and showed no toxicity ( > 12 mM) using 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.