Detection and identification of complex oxylipins in meadow buttercup (Ranunculus acris) leaves.

Screening of linolipins, i.e. galactolipids containing esterified residues of divinyl ether oxylipins, in the leaves of several higher plants revealed the presence of these complex oxylipins in the meadow buttercup leaves. The rapid accumulation of linolipins occurred in the injured leaves of meadow buttercup, while intact leaves possessed no linolipins. These oxylipins were isolated from the injured leaves, separated and purified by HPLC. The structural analyses of linolipins by UV, mass-spectroscopy and NMR spectroscopy resulted in the identification of eight molecular species. Three of them were identical to linolipins B-D found earlier in the leaves of flax (Linum usitatissimum L.). Other molecular species were identified as 1-O-(ω5Z)-etherolenoyl-2-O-dinor-(ω5Z)-etherolenoyl-3-O-ß-D-galactopyranosyl-sn-glycerol, 1-O-(ω5Z)-etherolenoyl-2-O-(7Z,10Z,13Z)-hexadecatrienoyl-3-O-ß-D-galactopyranosyl-sn-glycerol, 1-O-(ω5Z)-etherolenoyl-2-O-(7Z,10Z)-hexadecadienoyl-3-O-ß-D-galactopyranosyl-sn-glycerol, 1-O-(ω5Z)-etherolenoyl-2-O-α-linolenoyl-3-O-ß-D-galactopyranosyl-sn-glycerol, and 1-O-(ω5Z)-etherolenoyl-2-O-palmitoyl-3-O-(α-galactopyranosyl-1-6-ß-D-galactopyranosyl)-sn-glycerol. The trivial names "linolipins E, F, G, H and I," respectively, have been ascribed to these novel complex oxylipins.

Isolation and structure elucidation of linolipins C and D, complex oxylipins from flax leaves.

Two complex oxylipins (linolipins C and D) were isolated from the leaves of flax plants inoculated with phytopathogenic bacteria Pectobacterium atrosepticum. Their structures were elucidated based on UV, MS and NMR spectroscopic data. Both oxylipins were identified as digalactosyldiacylglycerol (DGDG) molecular species. Linolipin C contains one residue of divinyl ether (ω5Z)-etherolenic acid and one α-linolenate residue at sn-1 and sn-2 positions, respectively. Linolipin D possesses two (ω5Z)-etherolenic acid residues at both sn-1 and sn-2 positions. The rapid formation (2-30min) of linolipins C and D alongside with linolipins A and B occurred in the flax leaves upon their damage by freezing-thawing.

Unprecedented pathogen-inducible complex oxylipins from flax--linolipins A and B.

Oxylipins constitute a large family of bioregulators, biosynthesized via unsaturated fatty acid oxidation. This study reports the detection of an unprecedented family of complex oxylipins from flax leaves. Two major members of this family, compounds 1 and 2, were isolated and purified. Their structures were evaluated using NMR and MS analyses. Both compounds were identified as monogalactosyldiacylglycerol species. Compound 1 contains one alpha-linolenoyl residue and one residue of (9Z,11E,1'Z,3'Z)-12-(1',3'-hexadienyloxy)-9,11-dodecadienoic, (omega5Z)-etherolenic acid at positions sn-1 and sn-2, respectively. Compound 2 possesses (omega5Z)-etherolenic acid residues at both position sn-1 and position sn-2. We suggest the trivial names linolipin A and linolipin B for compounds 1 and 2, respectively, and the collective name linolipins for this new family of complex oxylipins. The linolipin content of flax leaves increased significantly in response to pathogenesis. Thus, accumulation of esterified antimicrobial divinyl ethers may be of relevance to plant defense.