Plakortides I–L, four new cyclic peroxides from an undescribed Jamaican sponge Plakortis sp. (Homosclerophorida, Plakinidae)

Four new polyketide-derived cyclic peroxides, plakortides I (1), J (2), K (3) and L (4), were isolated from an undescribed sponge of the genus Plakortis collected at Discovery Bay, Jamaica. The structures were elucidated by spectral analysis including the 2D NMR techniques. The relative stereochemistry of the plakortides was established by NOESY NMR experiments. Plakortide I (1) represents the first report of a polyketide-derived cyclic peroxide with an α,β-unsaturated ketone moiety in the side chain and exhibits significant antimalarial activity against the W2 Clone of Plasmodium falciparum with an IC50 of 570 ng mL−1 and a selectivity index of >8.4.