Docosapentaenoic acid (DPA), a C22:5 long-chain ω3 or ω6 polyunsaturated fatty acid (PUFA), is found in algal and fish oils, created via linoleic acid metabolism and is a metabolite in DHA metabolism. It can be acted upon by lipoxygenases to produce mono-, di- and tri-hydroxy derivatives in neutrophils and macrophages. These DPA derivatives are another branch of the specialised proresolving mediators (SPMs) produced from long-chain fatty acids which have anti-inflammatory properties, even though mechanisms of their anti-inflammatory action have not been fully elucidated (Bannenberg & Serhan 2010, Dangi et al. 2010, Vik et al. 2017, Hansen et al. 2017).
The biosynthesis of SPMs derived from the two isomers of DPA, DPAn-6 (cis-4,7,10,13,16-docosapentaenoic acid) and DPAn-3 (cis-7,10,13,16,19-docosapentaenoic acid), is described here. The only difference between the two isomers is the position of the first double bond; ω-3 for DPAn-3 and ω-6 for DPAn-6. The products of these isomers were characterised by analogy in structure and action to docosahexaenoic acid (DHA)-derived and eicosapentaenoic acid (EPA)-derived resolvins, protectins and maresins (Serhan et al. 2002, Bannenberg & Serhan 2010, Serhan et al. 2015).