Marine eicosanoids: Occurrence of 8,11,12-trihydroxylated eicosanoic acids in starfishes

Steric analysis of epoxyalcohol and trihydroxy derivatives of 9-hydroperoxy-linoleic acid from hematin and enzymatic synthesis

We characterize the allylic epoxyalcohols and their trihydroxy hydrolysis products generated from 9R- and 9S-hydroperoxy-octadecenoic acid (HPODE) under non-enzymatic conditions, reaction with hematin and subsequent acid hydrolysis, and enzymatic conditions, incubation with Beta vulgaris containing a hydroperoxide isomerase and epoxide hydrolase. The products were resolved by HPLC and the regio and stereo-chemistry of the transformations were determined through a combination of (1)H NMR and GC-MS analysis of dimethoxypropane derivatives. Four trihydroxy isomers were identified upon mild acid hydrolysis of 9S,10S-trans-epoxy-11E-13S-hydroxyoctadecenoate: 9S,10R,13S, 9S,12R,13S, 9S,10S,13S and 9S,12S,13S-trihydroxy-octadecenoic acids, in the ratio 40:26:22:12. We also identified a prominent δ-ketol rearrangement product from the hydrolysis as mainly the 9-hydroxy-10E-13-oxo isomer. Short incubation (5 min) of 9R- and 9S-HPODE with B. vulgaris extract yielded the 9R- and 9S-hydroxy-10E-12R,13S-cis-epoxy products respectively. Longer incubation (60 min) gave one specific hydrolysis product via epoxide hydrolase, the 9R/S,12S,13S-trihydroxyoctadecenoate. These studies provide a practical approach for the isolation and characterization of allylic epoxy alcohol and trihydroxy products using a combination of HPLC, GC-MS and (1)H NMR.

Chemical constituents and bioactivities of starfish

Starfish have been the research topic in many chemical and pharmacological laboratories due to their complex secondary metabolites and diverse bioactivities. The aim of this review is to provide an up-to-date review on the chemistry and bioactivity of compounds isolated from all kinds of starfish to illustrate the chemodiversity and biological significance of these constituents, along with their geographical distribution where it is discernible.

Biosynthesis and functions of eicosanoids generated by the coelomocytes of the starfish, Asterias rubens

Eicosanoids are a group of oxygenated fatty acid derivatives formed from C20 polyunsaturated fatty acids, including arachidonic and eicosapentaenoic acids. The potential of the coelomocytes of the starfish, Asterias rubens, to generate eicosanoids through the cyclooxygenase (COX) and lipoxygenase (LOX) pathways was investigated using reverse-phase high performance liquid chromatography, enzyme immunoassay and gas chromatography-mass spectrometry. The principal LOX product was identified as 8-hydroxyeicosatetraenoic acid (8-HETE) with 8-hydroxyeicosapentaenoic acid (8-HEPE) synthesised at significantly lower levels. No classical prostaglandins (PG), such as PGE2 or PGD2, were found to be generated by ionophore-challenged coelomocytes. Incubation of coelomocytes with lipopolysaccharides from either Escherichia coli or Salmonella abortus failed to induce an increase in generation of LOX products and the presence of 8-HETE (0-25 microM) had no significant effect on the in vitro phagocytic activity of Asterias coelomocytes. Neither indomethacin (a COX inhibitor) or esculetin (a LOX inhibitor) had any effect on the clearance of the bacterium, Vibrio splendidus, from the coelomic cavity of starfish suggesting that products of these enzymes are not involved in such coelomocyte responses to foreign particles.

Egg hatching activity of trihydroxylated eicosanoids in the barnacle Balanus balanoides

Previous work has shown that eicosanoid hatching factors can be isolated from tissues of a variety of barnacle species. To further investigate the nature of barnacle hatching factor an eicosanoid fraction isolated from homogenates of the barnacle Balanus balanoides was purified on RP-HPLC and trihydroxy fatty acid fractions were bioassayed for hatching activity and analysed by GC-MS. The identified eicosanoids were 8,11,12-trihydroxy-5,9,14-eicosatrienoic acid, 8,11,12-trihydroxy-5,9,14,17-eicosatetraenoic acid, 10,11,12-trihydroxy-5,8,14,17-eicosatetraenoic acid and 10,13, 14-trihydroxy-4,7,11,16,19-docosapentaenoic acid. These studies suggest that barnacles possess a potent n-9 lipoxygenase which can metabolise either arachidonic acid, eicosapentaenoic acid or docosahexaenoic acid. The predominant eicosanoids common to all active fractions were either 8,11,12-trihydroxyeicosatrienoic acid or an isomer of 8,11-12-trihydroxyeicosatetraenoic acid, which suggests that a particular configuration of an 8,11,12 triol is barnacle hatching factor.