Occurrence and biosynthesis of 11(R)-hydroxy-eicosatetraenoic acid (11-R-HETE) in the Caribbean soft coral Plexaurella dichotoma

Gorgonian soft corals from the Caribbean Sea are known to contain prostaglandin-like compounds as well as other products of arachidonic acid lipoxygenation, and the formation of the latter has been suggested to represent the first step in prostaglandin biosynthesis. Here we present evidence for the presence of 11-R-hydroxy-5Z,8Z,12E,14Z-eicosatetraenoic acid (11-R-HETE), as well as of the enzyme responsible for its biosynthesis, in the Caribbean gorgonian Plexaurella dichotoma. Lipid extracts from P. dichotoma were purified by conventional SiO2 column chromatography followed by reversed phase high-pressure liquid chromatography (HPLC). These yielded a component having chromatographic and spectroscopic properties identical to synthetic 11-HETE. Electron impact mass spectrometric analysis of the acetoxy-, methyl ester derivative of the compound confirmed its identity as 11-HETE, while chiral phase HPLC of the methyl ester derivative showed that the stereochemistry of the alcoholic carbon atom was R. Enzymatically active homogenates from P. dichotoma were able to convert both unlabelled and [H-3]arachidonic acid into 11-HETE. In vitro biosynthesis of the latter metabolite was also observed with homogenates of the Mediterranean gorgonian Paramuricea clavata, another non-prostaglandin-containing soft coral, thus suggesting that 11-R-HETE production is not necessarily accompanied by prostaglandin formation in gorgonian corals.