Fragmentation of a linoleate-derived γ-hydroperoxy-α,β-unsaturated epoxide to γ-hydroxy- and γ-oxo-alkenals involves a unique pseudo-symmetrical diepoxycarbinyl radical

Many of the pathological effects of lipid peroxidation are mediated by aldehydes generated through fragmentation of lipid peroxides. Among these aldehydes, the γ-hydroxy- and γ-oxo-α,β-alkenals, e.g., 4-hydroxy-2-nonenal (HNE) and 4-oxo-2-nonenal (ONE), are especially prone to modifying proteins and DNA through covalent adduction. In addition the "mirror image" γ-hydroxy- and γ-oxo-α,β-alkenal phospholipids can serve as high-affinity ligands for biological receptors triggering pathology. Therefore, the mechanisms by which these aldehydes are generated in vivo are under intense scrutiny. We now report observations supporting the intermediacy of a unique pseudo-symmetrical diepoxycarbinyl radical that accounts for the coproduction of HNE, ONE, and their mirror image analogues 9-hydroxy-12-oxo-10(E)-dodecenoic acid and 9-keto-12-oxo-10-dodecenoic acid upon fragmentation of 13-hydroperoxy-cis-9,10-epoxyoctadeca-11-enoic acid.     

Detection of an enol intermediate in the hydroperoxide lyase chain cleavage reaction

Guava (Psidium guajava) hydroperoxide lyase (HPL) preparations were incubated with [1-(14)C](9Z,11E,13S,15Z)-13-hydroperoxy-9,11,15-octadecatrienoic acid for 1 min at 0 degrees C, followed by rapid extraction/trimethylsilylation. Analysis of the trimethylsilylated products by gas chromatography-mass spectrometry and radio-high-performance liquid chromatography revealed a single predominant (14)C-labelled compound, identified by its (1)H-nuclear magnetic resonance, ultraviolet and mass spectra as the trimethylsilyl ether/ester of (9Z,11E)-12-hydroxy-9,11-dodecadienoic acid. Longer time incubations afford smaller yield of this enol due to its partial tautomerization into (9Z)-12-oxo-9-dodecenoic acid. The data obtained demonstrate that formation of (9Z)-12-oxo-9-dodecenoic acid in the HPL reaction is preceded by unstable enol oxylipin, and further suggest that hemiacetals are the true products of HPL catalysis.     

The “heterolytic hydroperoxide lyase” is an isomerase producing a short-lived fatty acid hemiacetal

To elucidate the reaction mechanism of hydroperoxide lyase (HPL), the enzyme from guava (Psidium guajava) fruits, was incubated for 10–60 s at 0 °C with 13-HPOT. The products were rapidly extracted and derivatized by trimethylsilylation. Two trapping products, namely the trimethylsilyl ether/ester derivatives of the hemiacetal 12-(1′-hydroxy-3′-hexenyloxy)-9,11-dodecadienoic acid and the enol (9Z,11E)-12-hydroxy-9,11-dodecadienoic acid, were detected by gas chromatography-mass spectrometry (GC-MS) analyses. The structural assignments were supported by mass spectra recorded for (a) hydrogenated products; (b) products biosynthesized from [9,10,12,13,15,16] 13-HPOT or [¹⁸O₂]13-HPOT; (c) chemically prepared reference compounds. Kinetic experiments showed that the hemiacetal and enol were both unstable and transiently appearing compounds (half-lives, ca. 20 s and 2 min, respectively). Hemiacetal and enol biosynthesized from [¹⁸O₂]13-HPOT retained two and one ¹⁸O atoms, respectively, whereas no ¹⁸O was incorporated from [¹⁸O]water. The data demonstrated that: (1) the true enzymatic product formed from 13-HPOT in the presence of HPL is a short-lived hemiacetal; (2) the hemiacetal spontaneously dissociates into (3Z)-hexenal and the unstable enol form of (9Z)-12-oxo-9-dodecenoic acid; (3) the enzymatic isomerization of 13-HPOT into the hemiacetal occurs homolytically.     

Acid-catalyzed transformation of 13(S)-hydroperoxylinoleic acid into epoxyhydroxyoctadecenoic and trihydroxyoctadecenoic acids

Acid treatment of (13S)-(9Z,11E)-13-hydroperoxy-9,11-octadecadienoic acid in tetrahydrofuran-water solvent afforded mainly (11R,12R,13S)-(Z)-12,13-epoxy-11-hydroxy-9-octadecenoic acid, diastereomeric (Z)-11,12,13-trihydroxy-9-octadecenoic acids and four isomers of (E)-9,12,13(9,10,13)-trihydroxy-10(11)-octadecenoic acid. Other minor products were oxooctadecadienoic, (E)-9(13)-hydroxy-13(9)-oxo-10(11)-octadecenoic and (E)-12-oxo-10-dodecenoic acids. A heterolytic mechanism for acid catalysis was indicated, even though most of the products characterized also have been observed as a result of homolytic decomposition of the hydroperoxide via an oxy radical. Most of the products found in this study have been observed as metabolites of (13S)-(9Z,11E)-13-hydroperoxy-9,11-octadecadenoic acid in biological systems, and analogous compounds have been reported as metabolites of (12S)-(5Z,8Z,10E, 14Z)-12-hydroperoxy-5,8,10,14-hydroperoxy-5,8,10,14-eicosatetraenoic acid in either blood platelets or lung tissue.     

C12 derivatives of the hydroperoxide lyase pathway are produced by product recycling through lipoxygenase-2 in Nicotiana attenuata leaves

In response to diverse stresses, the hydroperoxide lyase (HPL) pathway produces C(6) aldehydes and 12-oxo-(9Z?)-dodecenoic acid ((9Z?)-traumatin). Since the original characterization of (10E?)-traumatin and traumatic acid, little has been added to our knowledge of the metabolism and fluxes associated with the conversion of (9Z?)-traumatin into diverse products in response to wounding and herbivory. A liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) method was developed to quantify C(12) derivatives of the HPL pathway and to determine their metabolism after wounding and simulated herbivory in Nicotiana attenuata leaves. Ninety-eight per cent of the (9Z?)-traumatin produced was converted to 9-hydroxy-(10E?)-traumatin (9-OH-traumatin); two-thirds by product recycling through lipoxygenase-2 (NaLOX2) activity and one-third by nonenzymatic oxidation. Thirty-eight per cent of the de novo produced 9-OH-traumatin was conjugated to glutathione, consistent with this oxylipin being a reactive electrophile species. 12-OH-(9Z?)-dodecenoic and dodecenedioic acids also showed rapid increases after wounding and simulated herbivory and a role for C(12) derivatives as signals in these processes was consistent with their ability to elicit substantial changes in gene expression. These results underscore the importance of metabolite reflux through LOX2, an insight which creates new opportunities for a functional understanding of C(12) derivatives of the HPL pathway in the regulation of stress responses.     

Convergence of the 5-LOX and COX-2 pathways: heme-catalyzed cleavage of the 5S-HETE-derived di-endoperoxide into aldehyde fragments

Oxygenation of the 5-lipoxygenase product 5S-hydroxyeicosatetraenoic acid by cyclooxygenase-2 yields a bicyclic di-endoperoxide. The di-endoperoxide contains two peroxides spanning from carbons 9 to 11 and 8 to 12, and two hydroxyls at carbons 5 and 15 of arachidonic acid (Schneider C., et al. 2006. Convergent oxygenation of arachidonic acid by 5-lipoxygenase and cyclooxygenase-2. J. Am. Chem. Soc. 128: 720). Here, we report that treatment of the di-endoperoxide with hematin or ferrous chloride results in cleavage of both peroxide O-O bonds and of the bonds between the carbons that carry the peroxide groups, producing the aldehydes 4-hydroxy-2E-nonenal (4-HNE), 8-oxo-5S-hydroxy-6E-octenoic acid, and malondialdehyde (MDA). The hematin- and ferrous iron-catalyzed transformation of the di-endoperoxide proceeded with a similar yield of products as the cleavage of the prostaglandin endoperoxide PGH₂ to 12S-hydroxy-5Z,8E,10E-heptadecatrienoic acid and MDA. Chiral phase HPLC analysis of the 4-HNE cleavage product showed greater than 98% 4S and thus established the S configuration of the 15-carbon of the di-endoperoxide that had not previously been assigned. This transformation of the 5-lipoxygenase/cyclooxygenase-2 derived di-endoperoxide invokes the possibility of a novel pathway to formation of the classic lipid peroxidation products 4-HNE and MDA.     

Linoleate 9R-dioxygenase and allene oxide synthase activities of Aspergillus terreus

Oxygenation of linoleic acid by Aspergillus terreus was studied with LC-MS/MS. 9(R)-Hydroperoxy-10(E),12(Z)-octadecadienoic acid (9R-HpODE) was identified along with 10(R)-hydroxy-8(E),12(Z)-octadecadienoic acid and variable amounts of 8(R)-hydroxy-9(Z),12(Z)-octadecadienoic acid. 9R-HpODE was formed from [11S-²H]18:2n − 6 with loss of the deuterium label, suggesting antarafacial hydrogen abstraction and oxygenation. Two polar metabolites were identified as 9-hydroxy-10-oxo-12(Z)-octadecenoic acid (α-ketol) and 13-hydroxy-10-oxo-11(E)-octadecenoic acid (γ-ketol), likely formed by spontaneous hydrolysis of an unstable allene oxide, 9(R),10-epoxy-10,12(Z)-octadecadienoic acid. α-Linolenic acid and 20:2n − 6 were oxidized to hydroperoxy fatty acids at C-9 and C-11, respectively, but α- and γ-ketols of these fatty acids could not be detected. The genome of A. terreus lacks lipoxygenases, but contains genes homologous to 5,8-linoleate diol synthases and linoleate 10R-dioxygenases of aspergilli. Our results demonstrate that linoleate 9R-dioxygenase linked to allene oxide synthase activities can be expressed in fungi.     

Formation of 12-oxo-trans-10-dodecenoic acid in chloroplasts from Thea sinensis leaves

Linolenic acid-[1-¹⁴C] was converted to 12-oxo-trans-10-dodecenoic acid, via 12-oxo-cis-9-dodecenoic acid by incubation with chloroplasts of Thea sinensis leaves. Thus, it was confirmed that linolenic acid is split into a C₁₂-oxo-acid, 12-oxo-trans-10-dodecenoic acid, and a C₆-aldehyde, trans-2-hexenal, leaf aldehyde, by an enzyme system in chloroplasts of tea leaves.     

n-Hexanal and (Z)-3-hexenal are generated from arachidonic acid and linolenic acid by a lipoxygenase in Marchantia polymorpha L.

Most terrestrial plants form green leaf volatiles (GLVs), which are mainly composed of six-carbon (C6) compounds. In our effort to study the distribution of the ability of lipoxygenase (LOX) to form GLVs, we found that a liverwort, Marchantia polymorpha, formed n-hexanal and (Z)-3-hexenal. Some LOXs execute a secondary reaction to form short chain volatiles. One of the LOXs from M. polymorpha (MpLOX7) oxygenized arachidonic and α-linolenic acids at almost equivalent efficiency and formed C6-aldehydes during its catalysis; these are likely formed from hydroperoxides of arachidonic and α-linolenic acids, with a cleavage of the bond between carbon at the base of the hydroperoxy group and carbon of double bond, which is energetically unfavorable. These lines of evidence suggest that one of the LOXs in liverwort employs an unprecedented reaction to form C6 aldehydes as by-products of its reaction with fatty acid substrates.     

Oxidation of [1-C]linoleic acid in isolated microsomes from pea leaves

The oxidation of [1-¹⁴C]linoleate in isolated microsomes from pea leaves was found to be stimulated by NADPH addition. The formation of one of the main metabolites, 12-hydroxy-9(Z)-dodecenoic acid is particularly NADPH-dependent. The predominant products in the absence of NADPH were hydroperoxides and in the presence of NADPH, 12-hydroxy-9(Z)-dodecenoic acid. Exogenous [1-¹⁴C]-13-hydroperoxy-9(Z), 11(E)-octadecadieoic acid and [1-¹⁴C]-12-oxo-9(Z)-dodecenoic acidwere the efficient precursors of 12-hydroxy9(Z)-dodecenoic acid. It was concluded that 12-hydroxy-9(Z)-dodecenoic acid is formed by NADPH-dependent enzymatic reduction of 12oxo-9(Z)-dodecenoic acid. The observed inhibition of linoleate oxidation in isolated microsomes by CO and metryapone suggests the involvement of cytochrome P-450 in the reaction. The relative contribution of lipoxygenase and monooxygenase activity to linoleate oxidation in microsomes is discussed.     

Metabolism of Unsaturated Monogalactosyldiacylglycerol Molecular Species in Arabidopsis thaliana Reveals Different Sites and Substrates for Linolenic Acid Synthesis

Synthesis of unsaturated monogalactosyldiacylglycerol (MGDG) was examined in a mutant of Arabidopsis thaliana (L.) Heynh. containing reduced levels of hexadecatrienoic (16:3) and linolenic (18:3) acids in leaf lipids. Molecular species composition and labeling kinetics following the incorporation of exogenous [¹⁴C]fatty acids suggest that at least two pathways and multiple substrates are involved in desaturation of linoleic acid (18:2) to 18:3 for production of unsaturated galactolipids. A reduction in 18:3/16:3 MGDG and an increase in 18:2/16:2 MGDG, together with labeling kinetics of these molecular species following the incorporation of exogenous [¹⁴C]12:0 fatty acids, suggests that a chloroplastic pathway for production of 18:3 at the sn-1 position of MGDG utilizes 18:2/16:2 MGDG as a substrate. This chloroplastic (prokaryotic) pathway is deficient in the mutant. When exogenous [¹⁴C]18:1 was supplied, a eukaryotic (cytoplasmic) pathway involving the desaturation of 18:2 to 18:3 on phosphatidylcholine serves as the source of 18:3 for the sn-2 position of MGDG. This eucaryotic pathway predominates in the mutant.     

Is strain DS5 hydratase a C-10 positional specific enzyme? Identification of bioconversion products from α- and γ-linolenic acids byFlavobacterium sp. DS5

Summary Previously, we reported the isolation of a new microbial strain,Flavobacterium sp. DS5 (NRRL B-14859) which converted oleic and linoleic acids to their corresponding 10-keto- and 10--ydroxy-fatty acids. The hydration enzyme seemed to be specific to the C-10 position. Now we have identified, by GC/MS, NMR, and FTIR, the bioconversion products from -linolenic acid as 10-hydroxy-12(Z), 15(Z)-octadecadienoic acid and from -linolenic acid as 10-hydroxy-6(Z), 12(Z)-octadecadienoic acid. Products from 9(E)-unsaturated fatty acids were also identified as their corresponding 10-hydroxy or 10-keto fatty acids. From these results, it is concluded that strain DS5 hydratase is indeed a C-10 positional-specific enzyme and prefers an 18-carbon mono-unsaturated fatty acid. Among the C18 unsaturated fatty acids, an additional double bond on either side of the C-9 position lowers the enzyme hydration activity.     

Antiparasitic activity of prenylated benzoic acid derivatives from Piper species

Fractionation of dichloromethane extracts from the leaves of Piper heterophyllum and P. aduncum afforded three prenylated hydroxybenzoic acids, 3-[(2E,6E,10E)-11-carboxy-3,7,15-trimethyl-2,6,10,14-hexadecatetraenyl)-4,5-dihydroxybenzoic acid, 3-[(2E,6E,10E)-11-carboxy-13-hydroxy-3,7,15-trimethyl-2,6,10,14-hexadecatetraenyl]-4,5-dihydroxybenzoic acid and 3-[(2E,6E,10E)-11-carboxy-14-hydroxy-3,7,15-trimethyl-2,6,10,15-hexadecatetraenyl]-4,5-dihydroxybenzoic acid, along with the known compounds, 4,5-dihydroxy-3-(E,E,E-11-formyl-3,7,15-trimethyl-hexadeca-2,6,10,14-tetraenyl)benzoic acid (arieianal), 3,4-dihydroxy-5-(E,E,E-3,7,11,15-tetramethyl-hexadeca-2,6,10,14-tetraenyl)benzoic acid, 4-hydroxy-3-(E,E,E-3,7,11,15-tetramethyl-hexadeca-2,6,10,14-tetraenyl)benzoic acid, 3-(3,7-dimethyl-2,6-octadienyl)-4-methoxy-benzoic acid, 4-hydroxy-3-(3,7-dimethyl-2,6-octadienyl)benzoic acid and 4-hydroxy-3-(3-methyl-1-oxo-2-butenyl)-5-(3-methyl-2-butenyl)benzoic acid. Their structures were elucidated on the basis of spectroscopic data, including homo- and heteronuclear correlation NMR experiments (COSY, HSQC and HMBC) and comparison with data reported in the literature. Riguera ester reactions and optical rotation measurements established the compounds as racemates. The antiparasitic activity of the compounds were tested against three strains of Leishmania spp., Trypanosoma cruzi and Plasmodium falciparum. The results showed that 3-(3,7-dimethyl-2,6-octadienyl)-4-methoxy-benzoic acid exhibited potent and selective activity against L. braziliensis (IC₅₀ 6.5 μg/ml), higher that pentamidine used as control. Moreover, 3-[(2E,6E,10E)-11-carboxy-3,7,15-trimethyl- 2,6,10,14-hexadecatetraenyl)-4,5-dihydroxybenzoic acid and 4-hydroxy-3-(3-methyl-1-oxo-2-butenyl)-5-(3-methyl-2-butenyl)benzoic acid showed moderate antiplasmodial (IC₅₀ 3.2 μg/ml) and trypanocidal (16.5 μg/ml) activities, respectively.     

Antifungal 3-Hydroxy Fatty Acids from Lactobacillus plantarum MiLAB 14

We report the identification and chemical characterization of four antifungal substances, 3-(R)-hydroxydecanoic acid, 3-hydroxy-5-cis-dodecenoic acid, 3-(R)-hydroxydodecanoic acid and 3-(R)-hydroxytetradecanoic acid, from Lactobacillus plantarum MiLAB 14. The concentrations of the 3-hydroxy fatty acids in the supernatant followed the bacterial growth. Racemic mixtures of the saturated 3-hydroxy fatty acids showed antifungal activity against different molds and yeasts with MICs between 10 and 100 μg ml⁻¹.     

Profiles of glycerolipids in Pyropia haitanensis and their changes responding to agaro-oligosaccharides

A sensitive method based on electrospray ionization tandem mass spectrometry was used to profile glycerolipids in Pyropia haitanensis and their changes responding to agaro-oligosaccharides. Ten monogalactosyldiacylglycerols (MGDGs), twelve digalactosyldiacylglycerols (DGDGs), five sulfoquinovosyldiacylglycerols (SQDGs), five phosphatidylglycerols (PGs), fifteen phosphatidylcholins (PCs), three phosphatidic acids (PAs), and three phosphatidylethanolamines (PEs) were identified in P. haitanensis. We found the SQDG was the most abundant species, followed by MGDG, DGDG, PG, PC, PE, and PA of the total glycerolipids. The predominant lipid species contained C20 fatty acids at sn-1/sn-2 positions, which was different from higher plants. Changes in membrane lipid species occurred when P. haitanensis were treated with agaro-oligosaccharides. At first, agaro-oligosaccharides induced an increase in total glycerolipids including the galactolipids such as MGDG (20:5/20:5) and phospholipids such as PC (18:3/20:5), suggesting that agaro-oligosaccharides caused changes of lipids in chloroplasts and plasma membrane. With increased treatment time, a large decline in major plasma membrane lipids (PCs and PEs) was observed, but not galactolipids (MGDGs and DGDGs), suggesting that the lipid changes occurred mainly at the plasma membrane after prolonged treatment.     

Synthesis and biological activity of hydroxylated derivatives of linoleic acid and conjugated linoleic acids

Allylic hydroxylated derivatives of the C18 unsaturated fatty acids were prepared from linoleic acid (LA) and conjugated linoleic acids (CLAs). The reaction of LA methyl ester with selenium dioxide (SeO₂) gave mono-hydroxylated derivatives, 13-hydroxy-9Z,11E-octadecadienoic acid, 13-hydroxy-9E,11E-octadecadienoic acid, 9-hydroxy-10E,12Z-octadecadienoic acid and 9-hydroxy-10E,12E-octadecadienoic acid methyl esters. In contrast, the reaction of CLA methyl ester with SeO₂ gave di-hydroxylated derivatives as novel products including, erythro-12,13-dihydroxy-10E-octadecenoic acid, erythro-11,12-dihydroxy-9E-octadecenoic acid, erythro-10,11-dihydroxy-12E-octadecenoic acid and erythro-9,10-dihydroxy-11E-octadecenoic acid methyl esters. These products were purified by normal-phase short column vacuum chromatography followed by high-performance liquid chromatography (HPLC). Their chemical structures were characterized by liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance spectroscopy (NMR). The allylic hydroxylated derivatives of LA and CLA exhibited moderate in vitro cytotoxicity against a panel of human cancer cell lines including chronic myelogenous leukemia K562, myeloma RPMI8226, hepatocellular carcinoma HepG2 and breast adenocarcinoma MCF-7 cells (IC₅₀ 10-75 μM). The allylic hydroxylated derivatives of LA and CLA also showed toxicity to brine shrimp with LD₅₀ values in the range of 2.30-13.8 μM. However these compounds showed insignificant toxicity to honeybee at doses up to 100 μg/bee.     

绿叶挥发物产生特征及其生态生理作用研究进展

该文系统综述了植物绿叶挥发物(green leaf volatiles, GLVs)的形成特征、对植物的生态生理作用及调控机制等方面的最新研究进展。GLVs是指植物经十八碳烷酸途径过氧化物酶分支途径产生的含6个碳原子的醛、醇及其酯。除叶片外, 植物的根、茎、果实、种子等部位均可以合成该类化合物, 合成调控存在转录和转录后水平的调控。在特定植物中, GLVs合成及其组分还受到植物生长发育阶段和生长季节等外源环境的影响。昆虫啃食、微生物感染以及有益真菌的定植等生物逆境与缺氮等物理逆境均具有诱导GLVs合成的作用。除了参与植物特有气味形成外, GLVs在植物直接和间接防御应答中发挥着重要的作用。GLVs不仅具有抑制微生物和多种昆虫繁殖的作用, 还具有诱导多种防御化合物合成、预置(prime)有关信号途径的作用。基于GLVs在植物界的广泛存在性和在防御应答中的多层次作用, 该文作者提出了GLVs在道地药材品质形成中的潜在作用及开展相关研究的必要性和紧迫性。     

The "heterolytic hydroperoxide lyase" is an isomerase producing a short-lived fatty acid hemiacetal

To elucidate the reaction mechanism of hydroperoxide lyase (HPL), the enzyme from guava (Psidium guajava) fruits, was incubated for 10-60 s at 0 degrees C with 13-HPOT. The products were rapidly extracted and derivatized by trimethylsilylation. Two trapping products, namely the trimethylsilyl ether/ester derivatives of the hemiacetal 12-(1'-hydroxy-3'-hexenyloxy)-9,11-dodecadienoic acid and the enol (9Z,11E)-12-hydroxy-9,11-dodecadienoic acid, were detected by gas chromatography-mass spectrometry (GC-MS) analyses. The structural assignments were supported by mass spectra recorded for (a) hydrogenated products; (b) products biosynthesized from [9,10,12,13,15,16] 13-HPOT or [(18)O(2)]13-HPOT; (c) chemically prepared reference compounds. Kinetic experiments showed that the hemiacetal and enol were both unstable and transiently appearing compounds (half-lives, ca. 20 s and 2 min, respectively). Hemiacetal and enol biosynthesized from [(18)O(2)]13-HPOT retained two and one (18)O atoms, respectively, whereas no (18)O was incorporated from [(18)O]water. The data demonstrated that: (1) the true enzymatic product formed from 13-HPOT in the presence of HPL is a short-lived hemiacetal; (2) the hemiacetal spontaneously dissociates into (3Z)-hexenal and the unstable enol form of (9Z)-12-oxo-9-dodecenoic acid; (3) the enzymatic isomerization of 13-HPOT into the hemiacetal occurs homolytically.     

Lipids in Cruciferae IX. The Effect of Growth Temperature and Stage of Development on the Fatty Acid Composition of Leaves, Siliques and Seeds of "Zero-erucic-acid" Breeding Lines of Brassica napus

Two breeding lines of “zero-erucic-acid” rapeseed (Brassica napus) were grown in climate chambers at a constant night temperature (12°C) and constant photoperiod (16 hours) but with different day temperatures (15, 20 and 25°C). Samples of leaves, siliques and immature seeds were analysed for total fatty acid pattern. The content of different acyl lipids and the fatty acid pattern of these lipids were also determined in some of the samples by use of preparative TLC followed by GLC of the fatty acids. The mature seeds produced by ten plants of each selection in each climate were analysed separately for total fatty acid composition. Mono- and digalactosyl diglycerides (MGDG, DGDG) were the predominant acyl lipids in leaves and siliques. In developing seeds they also were more abundant than the phospholipids, but in this case the neutral lipids, mainly triacylglycerols, contained about 95% of the total fatty acids. Large variations were found in the fatty acid composition of monogalactosyl diglyceride and digalactosyl diglyceride, isolated from leaves, siliques and immature seeds. The palmitic acid content of leaf MGDG was about 15 %, atypically high for MGDG from photosynthetic tissue. The linolenic acid content of the MGDG was about 45 %, 30 % and 10 % in the leaf, silique and seed tissues respectively. A hexadecatrienoic acid (16: 3) was found almost exclusively in the MGDG samples of leaves, siliques and immature seeds (about 25 %, 10 % and 3 % 16:3 respectively). The lipids of siliques — mainly photosynthetising tissue — were different from those of leaves and had especially high contents of stearic acid (6–12 % in the different lipids). For all lipid classes studied, leaves grown at the lowest day temperature had a slightly lower oleic and higher linolenic acid content than those grown at the highest temperature. On the other hand, increasing the day temperature caused a decreased level of oleic, an increased level of linoleic and an essentially unchanged level of linolenic acids in the mature seeds from both selections.     

Identification of Traumatin, a Wound Hormone, as 12-Oxo-trans-10-dodecenoic Acid

12-Oxo-trans-10-dodecenoic acid (trans-10-ODA) is an oxidation product of polyunsaturated fatty acids in plant tissues. The structural similarity of trans-10-ODA and traumatic acid, a compound considered to be a wound hormone, suggested that trans-10-ODA might be a precursor of traumatic acid. Both trans-10-ODA and traumatic acid were active in the Wehnelt bean assay. The results were more consistent with trans-10-ODA than with traumatic acid. Cucumber (Cucumis sativus L. var. National Pickling) hypocotyls also showed a growth increase following treatment with trans-10-ODA, which suggested that trans-10-ODA has a more general influence on plant development than previously ascribed to traumatic acid.