Anthogorgienes A–O, New Guaiazulene-Derived Terpenoids from a Chinese Gorgonian Anthogorgia Species, and Their Antifouling and Antibiotic Activities

Fifteen new guaiazulene-based terpenoids designated anthogorgienes A–O (1–15) were isolated from a Chinese gorgonian Anthogorgia sp., together with eight known analogues (16–23). The structural patterns were classified into monomers, dimers, and trimers, which were supposed to be generated from a precursor guaiazulene and followed by side-chain and nucleus oxidation and oxidative rearrangement. The structures of new compounds were elucidated on the basis of extensive spectroscopic (IR, MS, and 1D and 2D NMR) data analysis. A possible biogenetic relationship of the isolated compounds was postulated. Some of the compounds showed potent antifouling activities against the larval settlement of barnacle Balanus amphitrite, whereas their antibiotic activities were also evaluated.