Arachidonic and eicosapentaenoic acids in Araucariaceae, a unique feature among seed plants

It is generally admitted that seed plants (spermaphytes) are unable to synthesize either arachidonic or eicosapentaenoic acids (AA and EPA), the classic essential fatty acids in animals. We give here chromatographic and spectrometric data showing that species from the primitive family Araucariaceae (gymnosperms) are able to synthesize AA and/or EPA in their seeds and leaves. Agathis robusta, in particular, contains AA and EPA in small amounts in its seeds, with no D5-unsaturated polymethylene-interrupted fatty acids (D5-UPIFA) with 18 carbon atoms, whereas Araucaria spp. contain both AA and C18 D5-UPIFA. In both species, D5-UPIFA with 20 carbon atoms are present as in all other Coniferophytes. All metabolic intermediates necessary for the biosynthesis of AA and/or EPA have been characterized in Araucariaceae seeds. The relevance of these observations is discussed with regard to the phylogeny of Coniferophytes.