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 pros taglandin-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 prese nt evidence for the presence of 11-R-hydroxy-5Z,8Z,12E,14Z-eicosatetra enoic acid (11-R-HETE), as well as of the enzyme responsible for its b iosynthesis, in the Caribbean gorgonian Plexaurella dichotoma. Lipid e xtracts from P. dichotoma were purified by conventional SiO2 column ch romatography followed by reversed phase high-pressure liquid chromatog raphy (HPLC). These yielded a component having chromatographic and spe ctroscopic properties identical to synthetic 11-HETE. Electron impact mass spectrometric analysis of the acetoxy-, methyl ester derivative o f the compound confirmed its identity as 11-HETE, while chiral phase H PLC 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]arachidoni c acid into 11-HETE. In vitro biosynthesis of the latter metabolite wa s also observed with homogenates of the Mediterranean gorgonian Paramu ricea clavata, another non-prostaglandin-containing soft coral, thus s uggesting that 11-R-HETE production is not necessarily accompanied by prostaglandin formation in gorgonian corals.