A novel natural phenyl alkene with cytotoxic activity

A novel phenyl alkene (1) was isolated from a mixture of three Florida sponges, Smenospongia aurea, Smenospongia cerebriformis, and Verongula rigida. Unlike terpenoids or amino acid derivatives, which are commonly known classes of secondary metabolites from these genera, the chemical structure of 1 showed an unprecedented linear phenyl alkene skeleton. Through comprehensive analyses of NMR and MS data, the gross structure of 1 was determined to be (E)-10-benzyl-5,7-dimethylundeca-1,5,10-trien-4-ol. The absolute configuration at C-4 was established as R by a modified Mosher's method. Based on the relative configuration between C-4 and C-7, the absolute configuration at C-7 was assigned as S. Compound 1 showed in vitro cytotoxic activity against HL-60 human leukemia cancer cells with an IC₅₀ value of 8.1 µM. Molecular docking study suggests that the structure of compound 1 matches the pharmacophore of eribulin required to display cytotoxic activity through the inhibition of microtubule activity.