Ceylonins G-I: spongian diterpenes from the marine sponge Spongia ceylonensis.

Three new spongian diterpenes, ceylonins G-I (1-3), were isolated from the marine sponge Spongia ceylonensis collected in Indonesia, together with five known spongian diterpenes (4-8). Only 4 inhibited USP7 with an IC50 value of 8.2 μM.