A new norcembranoid dimer from the red sea soft coral Sinularia gardineri

A study of Sinularia gardineri (Pratt) (Alcyoniidae), collected in the Red Sea, revealed a new heptacyclic norcembranoid dimer singardin (1). The structure of singardin was deduced by spectroscopic analysis. A known sesquiterpene, guaianediol (2), and the known cembranolides (1R,5S,8R,10S,11R)-11-hydroxy-1-isoprenyl-8-methyl-3,6-dioxo -5,8-epoxycyclotetradec-12-ene 10,12-carbolactone (5-epi-sinuleptolide) and sinuleptolide were also isolated. Compounds 1 and 2 show cytotoxicity to murine leukemia (P-388), human lung carcinoma (A-549), human colon carcinoma (HT-29), and human melanoma cells (MEL-28).