The marine sponge Plakortis zyggompha: a source of original bioactive polyketides

Three new spiculoic acids 1–3 and two members of a new closely related family of natural products named zyggomphic acids 4 and 5 were isolated from the very little studied marine sponge Plakortis zyggompha. Both families of compounds share a unique trans-hydrindan-2-one skeleton with six stereogenic centers. A total of 15 new metabolites were isolated from this sponge, all are of polyketide origin. The structures were elucidated using LC–MS, 1D, and 2D NMR methods. The absolute stereochemistry was determined by circular dichroism. The large number of close bioactive analogues allowed us to propose preliminary structure–activity relationships as antitumoral and antimycobaterial agents.