Hermann Schlenk

Furanoid fatty acids from fish lipids

Fatty acids, recently reported as constitutents of certain fish lipids, were identified to be derivatives of furan (furanoid fish fatty acids). 12,15-Epoxy-13,14-dimethyleicosa-12,14-dienoic acid is predominant among the furan acids and is associated withbis-homologs in regard to chain length. Monomethyl acids, such as 12,15-epoxy-13-methyleicosa-12,14-dienoic, are present in appreciable amounts. The structures were concluded from oxidative degradations, from mass spectrometry of methyl esters of the novel acids and fatty acids derived from them by opening the ring, and from nuclear magnetic resonance, infrared, and Raman spectra. The results from chemical procedures and from spectrometric methods were in aggreement with those obtained with authentic methyl 9,12-epoxyoctadeca-9,11-dienoate. The number of substituents at the furan ring greatly influences hydrogenation, hydrogenolysis, and hydrolysis reactions of the ring.

Arachidonic, 5, 11, 14, 17-eicosatetraenoic and related acids in plants舒Identification of unsaturated fatty acids

Arachidonic and related fatty acids which normally are found only in animals or microorganisms have been isolated and identified from several mosses and ferns. Fatty acids with a double bond in position 5, separated by more than one methylene group from other double bonds, have been found inGinkgo biloba andEquisetum. Analyses of fatty acids from numberous plants, in particular their chlorophyll containing parts, are listed according to components.The experimental part gives details on structure determination of the usual methylene-interrupted fatty acids by ozonization-hydrogenation-GLC. Alkaline isomerization combined with these procedures was applied to determine the unusual double bond structures. The method permits positional identification of an internal double bond.

Distribution of arachidonic and eicosapentaenoic acids in the lipids of mosses.

Lipid classes from four species of mosses, Mnium cuspidatum, and Mnium medium from Minnesota, and Hylocomium splendens and Pleurozium schreberi from Alaska, were analyzed. The total lipids of all species contained 30-40% arachidonic and eicosapentaenoic acids. However, the lipids from the Alaskan mosses contained about 75% neutral lipids (triacylglycerols, steryl esters and wax esters) whereas the lipids of the other species contained only 20% or less of these neutral lipids. Consistently, monogalactosyldiacylglycerols and phosphatidylethanol-amines were enriched in arachidonic acid and the galactolipids in eicosapentaenoic acid. The distribution of these acids in the phospholipids shows some preference for position 2. Together, the highly unsaturated C20 acids represented 80% of acyl groups in steryl esters. In triacylglycerols they were at average levels, while they were much less in sulfolipids and phosphatidylglycerols. Wax esters contained very little of the highly unsaturated acids but appreciable amounts of phytol and phytenic acid were found as wax constituents.

Retroconversion of docosahexaenoic acid in the rat.

Abstract 1. 1. Uniformly 14 C-labeled 4,7,10,13,16,19-docosahexaenoic acid was fed to normal rats and to rats at two stages of essential fatty acid deficiency. All groups incorporated about 17% of 14 C fed into liver lipids. Normal rats retroconverted the hexaenoic acid to 7,10,13,16,19-docosapentaenoic and 5,8,11,14,17-eicosapentaenoic acids. These three acids were in phospholipids and, to about 20%, in triglycerides. The deficient rats retroconverted the hexaenoic acid to a much lesser extent and radioactivity in their triglycerides was much lower. 2. 2. The radioactivity in the carboxyl groups of 4,7,10,13,16,19-docosahexaenoic and 5,8,11,14,17-eicosapentaenoic acids corresponded closely to an even distribution of 4 C in the chain. However, radioactivity in the carboxyl group of 7,10,13,16,19-docosapentaenoic acid was much lower than calculated for even distribution. At least 75% of this acid must have been reconstituted from a C 20 chain.

Methyl-directed desaturation of arachidonic to eicosapentaenoic acid in the fungus, Saprolegnia parasitica.

The lipids of Saprolegnia parasitica contain 5,8,11,14,17-eicosapentaenoic acid as major constituent. No other acid having (n-3) structure was detected, but 5,8,11,14-eicosatetraenoic (arachidonic) acid and its common precursors of (n-6) structure are present in significant amounts. During rapid growth of the organism, [1-14C]acetate was efficiently incorporated into fatty acids. Arachidonic acid was labeled after 2 h to nearly the same extent as any precursor acid and 14C in eicosapentaenoic acid reached this level within 6 h. Results of incubations with labeled fatty acids indicated that, in S. parasitica, oleic, linoleic, (6,9,12)-linolenic and arachidonic acids are major intermediates in the pathway to eicosapentaenoic acid. Methyl-directed desaturation of (n-6) to (n-3) acids does not occur with C18 acids but is specific for the polyunsaturated C20 chain length. Arachidonic acid is the direct precursor of eicosapentaenoic acid.

Synthesis and analysis of phytyl and phytenoyl wax esters

An efficient procedure for preparing phytenic acid methyl ester, free of isomers, from phytol is reported. Phytyl phytenate and other isoprenoid wax esters were synthesized. Gas liquid chromatography of these wax esters and other compounds related to phytol and phytenic acid is described. The alkyl constituents of isoprenoid wax esters can be analyzed after alkaline methanolysis and the acyl constituents after acidic methanolysis. The applicability of these methods to natural mixtures was demonstrated with wax esters from mosses which contained both types of isoprenoids and with wax esters from healthy and frost damaged grass which contained phytol, but not phytenic acid.

Paper chromatography of lipides

SummaryProcedures for qualitative and quantitative paper chromatography of lipides have been described in detail, together with some practical applications.With the monochain lipides it was found that one developing system serves universally. The long aliphatic chains essentially determine the chromatographic properties so that suitable conditions for chromatographing any lipide or lipide-like entity are predictable. For the same reason total analysis of natural mixtures cannot be done on one paper chromatogram due to superpositions.For complete analysis of natural mixtures of fatty acids it is advisable at the present time to combine paper chromatography with some other separation method. Distillation supplements best but requires gram quantities of material while paper chromatography is applicable on gamma or milligram scale. Chain-length analysis by paper chromatography and low-temperature chromatography have been introduced and are promising methods to approach a completely micro method for analyzing complex mixtures.

POSITIONAL ISOMERISM OF UNSATURATED FATTY ACIDS IN THE RAT. QUANTIFICATION OF ISOMERIC MIXTURES.

Mono- and dienoic acids of lipids from rat milk, rat sucklings, and rats on a fat-deficient diet were investigated. The percentage of uncommon isomers of palmitoleic acid was highest in milk, the newborn and the suckling rats, but receded after weaning. Isomers of linoleic acid were found only in traces in sucklings but became pronounced in rats on diets lacking essential fatty acids. The proportion of 8,11-diene among octadecadienoic acids increased markedly under such conditions within one week and two additional isomers became prominent after longer periods of fat-deficient diet.A supplement of hydrogenated coconut fat did not influence the occurrence of these isomers.Dietary petroselinic acid is incorporated by the rat into tissue lipids. 4-Hexadecenoic and a small amt of 8-eicosenoic acid arise from it.Quantification of isomeric mixtures by ozonization-hydrogenation and subsequent gas-liquid chromatography is discussed in detail.

Retroconversion of polyunsaturated fatty acids in vivo by partial degradation and hydrogenation

Abstract 1. 1. 4,7,10,13,16-Docosapentaenoate, randomly labelled with 14C was given to fat deficient rats. After 10 h about 13% of the radioactivity of all liver fatty acids was located in 5,8,11,14-eicosatetraenoic (arachidonic) acid. 2. 2. Degradation of the arachidonic acid by decarboxylation and by ozonization showed that random labelling has been maintained in the course of the conversion. Therefore, the retroconversion of the pentaenoic into the tetraenoic acid must imply, besides degradation by not more than two carbon atoms, the biohydrogenation of the double bond closest to the carboxyl group. 3. 3. Known procedures for decarboxylation of acids with HN3 + H2SO4 have been modified and a method has been developed for measuring the molarity of CO2 in hyamine + CH3OH on small scale. This permits convenient measurement of the molar activity of 14CO2 by scintillation counting.

Melting points of synthetic wax esters

Saturated, monoenoic and dienoic wax esters, C26−C40, have been synthesized from even-numbered fatty alcohols and acids. In homologous series of saturated esters, the increments of melting points follow a regular trend except for those esters which have an acid moiety two carbon atoms shorter than the alcohol moiety. These wax esters have melting points higher than interpolation would predict. Monoenoic wax esters with the double bond in the alcohol chain have melting points about 10 C higher than their isomers with the double bond in the acid chain.