Thielavins W–Z(7), New Antifouling Thielavins from the Marine-Derived Fungus Thielavia sp. UST030930-004

Eleven new depsides—thielavins W–Z (1–4) and thielavins Z(1)–Z(7) (5–11)—and also four known thielavins—A, H, J, and K (12–15)—were isolated from the ethyl acetate extract of a marine-derived fungal strain Thielavia sp UST030930-004. All of these compounds were evaluated for antifouling activity against cyprids of the barnacle Balanus (=Amphibalanus) amphitrite. The results showed that compounds 1–3 and 6–13 were active, with EC(50) values ranging from 2.95 ± 0.59 to 69.19 ± 9.51 μM, respectively. The inhibitive effect of compounds 1–3 and 7 was reversible. This is the first description of the antifouling activity of thielavins against barnacle cyprids.