Synthesis of four isomers of parinaric acid

A simple and reliable method for synthesizing four isomers of parinaric acid from alpha-linolenic acid (ALA) in high yields is described. The methylene-interrupted, cis triene system (1,4,7-octatriene) of ALA and common to other naturally occurring polyunsaturated fatty acids was transformed to a conjugated tetraene system (1,3,5,7-octatetraene). The synthesis involves bromination of ALA using 0.l M Br(2) in a saturated solution of NaBr in methanol, esterification of the fatty acid dibromides, double dehydrobromination by 1,8-diazabicyclo[5.4.0]undec-7-ene and saponification of the conjugated esters to a mixture of free conjugated acids. Addition of one molecule of bromine to the 12,13-double bond of ALA and subsequent dehydrobromination produces alpha-parinaric acid (9Z,11E,13E,15Z-octadecatetraenoic acid); addition of Br(2) to the 9,10-double bond or 15,16-double bond and then dehydrobromination and rearrangement yields 9E,11E,13E,15Z-octadecatetraenoic or 9E,11E,13E,15Z-octadecatetraenoic acids, respectively. The mixture of parinaric acid isomers is obtained in 65% yield, and the isomers can be purified by preparative HPLC; alternatively, the isomers can be converted by base catalyzed cis-trans isomerization (or by treatment with I(2)) to exclusively beta-parinaric acid (9E,11E,13E,15E-octadecatetraenoic acid). The various parinaric acid isomers were characterized by (1)H NMR, (13)C NMR, UV, GLC, HPLC and mass spectrometry.     

Elevated sulfatide levels in neurons cause lethal audiogenic seizures in mice

Galactosylceramide (GalCer) and 3- O -sulfo-GalCer (sulfatide) are abundant sphingolipids in myelinating glial cells. However, low levels of GalCer and sulfatide have also been found in neurons, though their physiological role in these cells is unknown. Transgenic mice over-expressing UDP-galactose : ceramide galactosyltransferase (CGT) under control of the Thy1.2 promoter synthesize C18 : 0 fatty acid containing GalCer and sulfatide in neurons. Depending on the genetic background, these transgenic mice have a significantly reduced life span. Transgenic mice were extremely sensitive to sound stimuli and displayed lethal audiogenic seizures after relatively mild acoustic stimulation, i.e., key jangling. CGT-transgenic mice additionally over-expressing the adenosine 3'-phospho 5'-phosphosulfate : cerebroside sulfotransferase were more sensitive to audiogenic seizure induction than mice expressing only the CGT-transgene. This correlated with the higher sulfatide content in neuronal plasma membranes of the double-transgenic mice compared with CGT-transgenic mice, and strongly suggests that lethal audiogenic seizures are caused by elevated sulfatide levels in transgenic neurons. CGT-transgenic mice will be a useful model to further investigate how sulfatide affects functional properties of neurons.     

Production of dicarboxylic acids from novel unsaturated fatty acids by laccase-catalyzed oxidative cleavage

The establishment of renewable biofuel and chemical production is desirable because of global warming and the exhaustion of petroleum reserves. Sebacic acid (decanedioic acid), the material of 6,10-nylon, is produced from ricinoleic acid, a carbon-neutral material, but the process is not eco-friendly because of its energy requirements. Laccase-catalyzing oxidative cleavage of fatty acid was applied to the production of dicarboxylic acids using hydroxy and oxo fatty acids involved in the saturation metabolism of unsaturated fatty acids in Lactobacillus plantarum as substrates. Hydroxy or oxo fatty acids with a functional group near the carbon–carbon double bond were cleaved at the carbon–carbon double bond, hydroxy group, or carbonyl group by laccase and transformed into dicarboxylic acids. After 8 h, 0.58 mM of sebacic acid was produced from 1.6 mM of 10-oxo-cis-12,cis-15-octadecadienoic acid (αKetoA) with a conversion rate of 35% (mol/mol). This laccase-catalyzed enzymatic process is a promising method to produce dicarboxylic acids from biomass-derived fatty acids.     

Bioreactor seaweed cell culture for production of bioactive oxylipins

Liquid cell suspension cultures derived from marine plants have the potential to biosynthesize novel biomedicinal compounds in a controlled environment. Of particular interest are the eicosanoids and related oxylipins emanating from the 15-lipoxygenase manifold of the arachidonic acid cascade, which is active in the brown algaLaminaria saccharina. Filamentous cell clumps ofL. saccharina isolated from female gametophytes were cultured in an illuminated bubble-column bioreactor in GP2 artificial seawater nutrient medium at 13 °C and air flow rate of 0.35 L air min^–1 L^–1 culture (vvm). Growth kinetics and biomass productivity data were obtained as a function of incident light intensity (2.4 to 98mol photon m^–2 s^–1) and initial cell density (27 to 149 mg DCW L^–1). Maximum cell densities exceeded 1200 mg DCW L^–1 after a 20 day cultivation time at optimal conditions of 98mol photon m^–2 s^–1 and 118 mg DCW L^–1 initial cell density. Qualitative analysis of chloroform/methanol extracts of the cell culture biomass by GC-MS confirmed the presence of the hydroxy fatty acids 13-HODTA and 13-HOTE, the likely products of 15-lipoxygenase catalyzed oxidation of linoleic or linolenic acids.     

Age-related contents of polymerized lipids in the ectohydric forest mosses Pleurozium schreberi and Hylocomium splendens

Cell wall preparations of the ectohydric forest mosses, Pleurozium schreberi (Brid.) Mitt. and Hylocomium splendens (Hedw.) B. S. G. contain polymerized lipids consisting of hydroxy acids, dicarboxylic acids, fatty acids, fatty alcohols and unidentified components. The finding of polymerized lipids in ectohydric mosses, which have highly permeable cell walls, indicates that the polymers do not form an effective barrier against water and nutrients, at least not in the cell walls of these mosses. The youngest parts of P. schreberi and H. splendens contained 2.0 and 1.6 mg polymerized lipids, respectively, on a dry cell wall weight basis. In the senescent, greyish-green parts of P. schreberi and in the one-year-old shoot tissue of H. splendens the corresponding amounts were about 1.5-fold. In both species the increase was due to increases in hydroxy acids, particularly dihydroxyhexadecanoic acids, dicarboxylic acids, unknown components and, in the case of H. splendens , also an increase in fatty acids. The increase may be related to the maturation of the cell walls. In still older shoot parts the amounts of polymerized lipids decreased in both species, and remained low until final decay of the tissues into small particles. A slight increase in the amount of the polymerized lipid monomers was found in the oldest and most decomposed parts of H. splendens , probably indicating a better resistance to decay than for other cell wall components. These findings are discussed in relation to what is known from the ectohydric peat-forming Sphagnum mosses.     

Fatty acid 2-Hydroxylation in mammalian sphingolipid biology

2-Hydroxy fatty acids (hFA) are important components of a subset of mammalian sphingolipids. The presence of hFA in sphingolipids is best described in the nervous system, epidermis, and kidney. However, the literature also indicates that various hFA-sphingolipids are present in additional tissues and cell types, as well as in tumors. Biosynthesis of hFA-sphingolipids requires fatty acid 2-hydroyxlase, and degradation of hFA-sphingolipids depends, at least in part, on lysosomal acid ceramidase and the peroxisomal fatty acid α-oxidation pathway. Mutations in the fatty acid 2-hydroxylase gene, FA2H, have been associated with leukodystrophy and spastic paraparesis in humans, underscoring the importance of hFA-sphingolipids in the nervous system. In the epidermis, hFA-ceramides are essential for the permeability barrier function. Physiological function of hFA-sphingolipids in other organs remains largely unknown. Recent evidence indicates that hFA-sphingolipids have specific roles in cell signaling.     

Subject index

Heats of fusion and heat capacities have been measured for saturated, unsaturated and hydroxy fatty acids, differing in degree of unsaturation, geometric isomerism, and position of unsaturated and hydroxy groups. Entropies of fusion are used to draw conclusions concerning molecular structure of fatty acid chains and lateral chain-chain interactions. Position of the functional group on the chain does not seem to significantly affect the entropy values for trans and cis single double bonds and single triple bonds, but differences are noted with hydroxy group position. Whereas single acid triglycerides of saturated acids have entropies which are about three times that of the corresponding acid, cis and trans single acid triglycerides do not show the same relationship with their corresponding acids. Comparing entropies of fusion for certain groups of fatty acids, only differing in carbon number, allows the estimation of chain equivalence with saturated fatty acids. Hence, for example it is shown that a 22 to 23-carbon cis mono-unsaturated fatty acid is equivalent to an 18-carbon saturated fatty acid.