J. R. Chipault

The determination of conjugatedcis-trans andtrans-trans methyl octadecadienoates by infrared spectrometry

SummaryPure conjugated methylcis-trans andtrans-trans octadecadienoates have been prepared and used to develop a method for the determination of these compounds by infrared spectrometry.Cis-trans compounds alone or in the presence oftrans-trans conjugation may be determined directly by the absorption at 10.55 μ. In the absence ofcis-trans isomers conjugatedtrans-trans octadienoates may be determined directly from the absorption at 10.11 μ. When both types of compounds are present however, a correction must be applied for the contribution of thecis-trans isomers to the 10.11 μ absorption of thetrans-trans material.

9,12,15-octadecatrien-6-ynoic acid, new acetylenic acid from mosses

Lipids of the moss,Ceratodon purpureus, yield up to 25% of an acetylenic acid which was identified as allcis-9,12,15-octadecatrien-6-ynoic acid. The methyl ester of this acid was isolated in 95% purity by gas liquid chromatography. Mass spectroscopy provided the mol wt and confirmed methyl stearate as product of hydrogenation. Ozonization indicated a triple bond in position 6 and a double bond in position 15. UV and IR spectra showedcis-double bonds, no conjugation, and notrans-double bonds. The Raman spectrum provided direct evidence for the triple bond and confirmed the presence of double bonds and the absence of conjugation. The ratio of intensities indicated 1 triple bond/3 double bonds. 9,12,15-Octadecatrien-6-ynoic acid has not previously been isolated from biological materials. It was found only in the triglycerides ofCeratodon purpureus and several other mosses. In contrast to arachidonic and eicosapentaenoic acids, the acetylenic acid seems to be restricted to few moss genera.

Lipid composition and (Na+ + K+)-ATPase activity in rat lens during triparanol-induced cataract formation

The development of triparanol cataracts in rats is accompanied by the loss of lens (Na+ + K+)-ATPase activity and by alteration in the lens content and composition of phospholipids, sterols and phospholipid acyl groups. The lipid changes occur along the same time course as the loss of (NA+ + K+)-ATPase activity. Triparanol feeding produces a decrease in lens phospholipid content. The percentage contents of phosphatidylcholine and phosphatidyl-serine decrease while the content of sphingomyelin substantially increases. The amounts of oleic acid in lens phospholipids decrease while stearic and palmitic acids increase; however, these changes are relatively small. Sterol content is also decreased while the percentage content of desmosterol increases markedly. Feeding of the cataractogenic agents galactose and diazacholesterol also alters the lens lipid compositions and (Na+ + K+)-ATPase activity. A loss of phosphatidylserine is the only change in lipid properties which always accompanies a loss of the enzyme activity. The possible relationships between the lens content of phosphatidylserine, (Na+ + K+)-ATPase activity and the mechanism of triparanol-induced cataract formation are discussed.

Occurrence of glyceryl tridocosahexaenoate in the eye of the sand troutCynoscion arenarius

The pigment epithelium of the eye of the sand trout (Cynoscion arenarius) contains a reflecting layer or tapetum lucidum, consisting of lipid spherules approximately 400 nm in diameter. The lipids consist amost exclusively of triglycerides and the fatty acids contain up to 95% docosahexaenoic acid. Thus the lipid of this reflecting layer appears to be nearly pure glyceryl tridocosahexaenoate. The adjacent tissues contain much less docosahexaenoic acid (retina 65%; choroid 9%) and little, if any, tridocosahexaenoin. The possible importance of this nearly pure, highly unsaturated, mono acid triglyceride is briefly discussed.

Interference of peroxides with the determination of total carbonyls in autoxidized fats

The contribution of hydroperoxides to the carbonyl content of autoxidized fats measured by a colorimetric 2,4-dinitrophenylhydrazone procedure has been studied. Carbonyls were determined in radiation oxidized methyl myristate, in autoxidized methyl esters of oleie, linoleic and linolenic acids and in autoxidized oils, before and after reduction of hydroperoxides to hydroxyl groups.The results indicate that hydroperoxides decompose to carbonyl compounds during the carbonyl determination and give carbonyl contents that are too high. The extent of the interference depends on the nature of the peroxides and, therefore, on the fatty acid composition of the material and on other factors probably associated with the conditions during autoxidation and subsequent storage. For these reasons it is not possible to apply a correction for peroxide interference based on the determined peroxide value.Carbonyl determinations on autoxidized lipids should be preceded by reduction of the peroxides to non-carbonyl compounds, and care should be taken to prevent losses of low molecular weight carbonyls during this procedure.

Lipids of the Triparanol Cataract in the Rat

The lipids of lenses from normal rats have been compared with those from cataractous and clearing lenses from rats fed triparanol. Desmosterol was about 1% of the sterols of normal lenses but amounted

Identification and characterization of fully deuterated fatty acids isolated fromScenedesmus obliquus cultured in deuterium oxide

The algaScenedesmus obliquus cultured in deuterated water, synthesized fully deuterated saturated and unsaturated long chain fatty acids. Their methyl esters were purified and their equivalent chain lengths were determined by gas liquid chromatography (GLC). They were characterized by mass spectroscopy, IR and near-IR spectroscopy, and NMR spectroscopy. Hexadeca-3,6-dienoic acid was identified. The fatty acid compositions of the total lipid and of individual lipid classes were measured. The melting point of methyl perdeuteriohexadecanoate was lower than that of its hydrogen counterpart. Methyl esters of perdeuterio fatty acids had shorter retention times in GLC chromatography on polar and nonpolar phases.

Conversion of conjugatedcis-trans octadecadienoates to thetrans-trans isomers1,2,3

SummaryThe conversion of methyl conjugatedcis-trans octadecadienoate to thetrans-trans isomer takes place easily in the presence of iodine and light. The reaction is more rapid in carbon disulfide than in Skellysolve C, and it is quite slow and accompanied by loss of conjugation in methanol. The rate of conversion increases with iodine concentration and light intensity and decreases with increasing fat concentration. It is affected by temperature also, but to a lesser degree. the influence of light may result from its catalytic effect on the decomposition of a reversible fat-iodine complex.The reaction appears to be pseudo-first order with respect to the substrate but is complicated by side reactions which inactivate the catalyst and destroy conjugation.The reaction occurs, at a measurable rate, with iodine in the dark, or in light without iodine, but no conversion takes place without iodine in darkness.The isomerization reaches an equilibrium when approximately 71% of the conjugation present is in thetrans-trans form. This equilibrium can be attained by starting with eithercis-trans ortrans-trans material. Very little, if any,cis-cis isomer is present in the equilibrium mixture.

Mass spectrometric identification of C20 fatty acids bovine lens using the pyrrolidide derivative

Unsaturated C20 fatty acids from bovine lens have been examined via gas chromatography-mass spectrometry of their pyrrolidine derivatives. The presence of arachidonic acid and 5,8,11-20∶3 in bovine lens has been confirmed by this study. In addition, the 10-, 11-, 12-, and 13-isomers of 20∶1 and the 7,13-, 8,14-, and 12,15-isomers of 20∶2 were identified.

Rapid micromethod for locating the oxirane group in 1,2-epoxides

Abstract A procedure for the analysis of micro amounts of epoxides is described. The method is based on the splitting of epoxides by periodic acid in a nonaqueous medium, followed by direct analysis of the reaction mixture by gas chromatography. The procedure is simple, rapid and requires only a few micrograms of material. The reaction is straightforward and yields no secondary products. The gas chromatographic analysis is sufficiently sensitive to detect small amounts of epoxy and non-epoxy impurities in addition to the major epoxide being analyzed. The method is not specific for epoxides, and its application to other substances capable of being split by periodic acid is discussed.