Secondary metabolites from the soft coral Sinularia arborea.

Two new 13-hydroxycembrane diterpenoids, arbolides A (1) and B (2), along with a known trihydroxysteroid, crassarosterol A (3), were isolated from the soft coral Sinularia arborea. The structures of new cembranes 1 and 2 were elucidated by spectroscopic methods. Steroid 3 was found to exhibit cytotoxicity toward K562 and MOLT-4 leukemia.