etheroleic-acid and vinyl-ether

Green tissues of spikemoss Selaginella martensii Spring possessed the complex oxylipins patterns. Major oxylipins were the products of linoleic and α-linolenic acids metabolism via the sequential action of 13-lipoxygenase and divinyl ether synthase (DES) or allene oxide synthase (AOS). AOS products were represented by 12-oxophytodienoic acid (12-oxo-PDA) isomers. Exceptionally, S. martensii possesses high level of 12-oxo-9(13),15-PDA, which is very uncommon in flowering plants. Separate divinyl ethers were purified after micro-preparative incubations of linoleic or α-linolenic acids with homogenate of S. martensii aerial parts. The NMR data allowed us to identify all geometric isomers of divinyl ethers. Linoleic acid was converted to divinyl ethers etheroleic acid, (11Z)-etheroleic acid and a minority of (ω5Z)-etheroleic acid. With α-linolenate precursor, the specificity of divinyl ether biosynthesis was distinct. Etherolenic and (ω5Z)-etherolenic acids were the prevailing products while (11Z)-etherolenic acid was a minor one. Divinyl ethers are detected first time in non-flowering land plant. These are the first observations of fatty acid metabolism through the lipoxygenase pathway in spikemosses (Lycopodiophyta).

Topics: alpha-Linolenic Acid; Cyclopentanes; Cytochrome P-450 Enzyme System; Fatty Acids, Unsaturated; Intramolecular Oxidoreductases; Linoleic Acid; Lipoxygenase; Nuclear Magnetic Resonance, Biomolecular; Oxylipins; Plant Proteins; Selaginellaceae; Vinyl Compounds

[1-14C]alpha-Linolenic acid was incubated with a particulate fraction of homogenate of leaves of the meadow buttercup (Ranunculus acris L.). The main product was a divinyl ether fatty acid, which was identified as 12-[1'(Z),3'(Z)-hexadienyloxy]-9(Z),11(E)-dodecadienoic acid. Addition of glutathione peroxidase and reduced glutathione to incubations of alpha-linolenic acid almost completely suppressed formation of the divinyl ether acid and resulted in the appearance of 13(S)-hydroxy-9(Z), 11(E),15(Z)-octadecatrienoic acid as the main product. This result, together with the finding that 13(S)-hydroperoxy-9(Z), 11(E),15(Z)-octadecatrienoic acid served as an efficient precursor of the divinyl ether fatty acid, indicated that divinyl ether biosynthesis in leaves of R. acris occurred by a two-step pathway involving an omega6-lipoxygenase and a divinyl ether synthase. Incubations of isomeric hydroperoxides derived from alpha-linolenic and linoleic acids with the enzyme preparation from R. acris showed that 13(S)-hydroperoxy-9(Z),11(E)-octadecadienoic acid was transformed into the divinyl ether 12-[1'(Z)-hexenyloxy]-9(Z), 11(E)-dodecadienoic acid. In contrast, neither the 9(S)-hydroperoxides of linoleic or alpha-linolenic acids nor the 13(R)-hydroperoxide of alpha-linolenic acid served as precursors of divinyl ethers.

Topics: alpha-Linolenic Acid; Chlorophyll; Color; Cytochrome P-450 Enzyme System; Ethers; Fatty Acids, Unsaturated; Lipoxygenase; Magnoliopsida; Oxidation-Reduction; Oxidoreductases; Plant Leaves; Plant Proteins; Vinyl Compounds