Identification of novel hydroxy fatty acids in the barnacle Balanus balanoides

Hepoxilins and trioxilins in barnacles: an analysis of their potential roles in egg hatching and larval settlement

The barnacle life cycle has two key stages at which eicosanoids are believed to be involved in cellular communication pathways, namely the hatching of nauplii and the settlement of cypris larvae. Barnacle egg-hatching activity has previously been reported to reside in a variety of eicosanoids, including 8-hydroxyeicosapentaenoic acid and a number of tri-hydroxylated polyunsaturated fatty acid derivatives, the trioxilins. The production of the eicosapentaenoic acid metabolite trioxilin A4 (8,11,12-trihydroxy-5,9,14,17-eicosatetraenoic acid) by the barnacles Balanus amphitrite and Elminius modestus was confirmed using a combination of high-performance liquid chromatography and gas chromatography, both linked to mass spectrometry. In addition, both species also generated trioxilin A3 (8,11,12-trihydroxy-5,9,14-eicosatrienoic acid; an arachidonic acid-derived product), 8,11,12-trihydroxy-9,14,17-eicosatrienoic acid (a omega3 analogue of trioxilin A3; derived from omega3 arachidonic acid) and 10,13,14-trihydroxy-4,7,11,16,19-docosapentaenoic acid (a docosahexaenoic acid-derived product). In contrast to earlier reports, trioxilin A3 had no E. modestus egg-hatching activity at any of the concentrations tested (10(-9)-10(-6) mol l(-1)). The unstable epoxide precursor hepoxilin A3, however, caused significant levels of hatching at 10(-6) mol l(-1). Furthermore, the stable hepoxilin B3 analogue PBT-3 stimulated hatching at 10(-7) mol l(-1). Neither trioxilin A3, hepoxilin A3 or PBT-3 at 0.25-30 micromol l(-1) served as settlement cues for B. amphitrite cypris larvae.

Natural halogenated fatty acids: their analogues and derivatives

A comprehensive survey has been made of all fatty acids containing halogen atoms covalently bonded to carbon and which are deemed as naturally occurring. Generally thought to be minor components produced by many different organisms, these interesting compounds now number more than 300. Recent research, especially in the marine area, indicates this number will increase in the future. Sources of halogenated fatty acids include microorganisms, algae, marine invertebrates, and higher plants and some animals. Their possible biological significance has also been discussed

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.