8(S)-HEPE is a monohydroxy fatty acid produced by lipoxygenase oxidation of EPA. It acts to promote hatching of barnacle eggs at 10 nM, although it is not clearly identified as the natural egg hatching factor.
(±)8-HEPE is produced by non-enzymatic oxidation of EPA. It contains equal amounts of 8(S)-HEPE and 8(R)-HEPE. The ability of (±)8-HEPE to induce hatching of E. modestus and B. balanoides eggs is probably due to the presence of the 8(R) isomer within the racemic mixture.[1][2] Reference:[1]. Shing, T.K.M., Gibson, K.H., Wiley, J.R., et al. First total synthesis of a barnacle hatching factor 8(R)-hydroxy-eicosa-5(Z),9(E),11(Z)-pentaenoic acid. Tetrahedron Letters 35, 1067-1070 (1994).[2]. Hill, E.M., and Holland, D.L. Identification and egg hatching activity of monohydroxy fatty acid eicosanoids in the barnacle Balanus balanoides. Proceedings of the Royal Society of London Series B.Biological Sciences 247, 41-46 (1991).
(±)18-HEPE is produced by non-enzymatic oxidation of EPA. It contains equal amounts of 18(S)-HEPE and 18(R)-HEPE. Specific biological activity attributed to (±)18-HEPE has not been documented.