Two new eunicellin-based diterpenoids from the South China Sea gorgonian Muricella sibogae Nutting

Two new eunicellin-based diterpenoids, sibogins A (1) and B (2), along with one known analogue (3), and four known 9,10-secosteroids (4-7), were isolated from the gorgonian Muricella sibogae Nutting collected from the South China Sea. The structures of the new compounds were elucidated by comprehensive analysis of spectroscopic data, especially by using 2D NMR spectra. The antifouling activity on barnacle Balanus amphitrite and lethality towards brine shrimp Artemia salina of all the isolated compounds were evaluated.