It is well known that cyclic peroxide products may be produced during the autoxidation of polyunsaturated fatty acids. In contrast with these labile compounds, several cyclic peroxides have been described in lipid extracts from marine sponges (Faulkner DJ, J Nat Prod 1997, 14, 259). Almost all these molecules are assumed to derive from the polyketide pathway and derived from a common backbone : CH3-(CO-CH2)n-COOH
The first of these compounds to be reported was plakortin, a six membered ring cycloperoxide found in 1978 by Faulkner’s group in the marine sponge Plakortis halicondrioides (Higgs M D et al., J Org Chem 1978, 43, 3454).
Subsequently, a series of related bioactive metabolites have been isolated. They include plakinic acids (Davidson, B. S. J. Org. Chem., 1991, 56, 6722), the strongly antifungal peroxyplakoric acids (Kobayashi M et al., Pharm Bull, 1993, 41, 1324) and the recently reported activators of cardiac Ca ATPase plakortones A-D (Patti AD et al., Tetrahedron 1996, 52, 377).
In 1998, several cyclic peroxide homologues have been described in the same sponge species, either active against cancer cell lines (Harrison B et al., J Nat Prod 1998, 61, 1033), toxic toward Artemia larvae (Braekman JC et al., J Nat Prod 1998, 61, 1038), inhibitor of the protozoan causing leishmaniasis (Compagnone RS et al., Tetrahedron 1998, 54, 3057), or without known biological activity (Fontana A et al., J Nat Prod 1998, 61, 1427). Several metabolites of plakortin with various cytotoxic activities have been also isolated from Plakortis simplex : dihydroplakortin and two dodecanoic derivatives (Cafieri F et al., Tetrahedron 1999, 55, 7045). Later, other related cytotoxic endoperoxides have been isolated from the Okinawan sponge Plakortis lita and named Haterumadioxins (Takada N et al., J Nat Prod 2001, 64, 356) and from Plakortis simplex (Holzwarth M et al., J Nat Prod 2005, 68, 759).