Phospholipids of Clostridium butyricum. IV. Analysis of the positional isomers of monounsaturated and cyclopropane fatty acids and alk-1′-enyl ethers by capillary column chromatography

Abstract

The positional isomers of the cyclopropane fatty acids of Clostridium butyricum phospholipids have been analyzed by capillary column gas–liquid chromatography. Greater than 95% of the methylenehexadecanoic acids was the 9,10 isomer. On the other hand, 60–70% of the hexadecenoic acid precursors was the Δ7 isomer, and the remainder was the Δ9 isomer. Of the methyleneoctadecanoic acids 75–80% was the 11,12 isomer, with the remainder being the 9,10 isomer. There were approximately equal amounts of the Δ9- and Δ11-octadecenoic acids in the phospholipids. This study reveals a surprisingly strong specificity of the cyclopropane synthetase for the (n-7) series of monoenoic fatty acids.An analysis by capillary column chromatography of the monoenoic and cyclopropane aldehyde dimethylacetals derived from the plasmalogens (1-alk-1′-enyl-2-acyl-glycerophosphatides) of C. butyricum revealed the presence of the same positional isomeric mixtures of the 16- and 18-carbon monoenoic residues in approximately the same ratios as were found in the fatty acids. In the formation of the cyclopropane alk-1′-enyl ethers there was also specificity for the (n-7) series, but it was not as strong as that seen in the fatty acids. The ratio of the 7,8 isomer to the 9,10 isomer was higher in the methylenehexadecanals than in the corresponding fatty acids. This paper extends the use of Golay capillary columns to the analysis of the positional isomers of plasmalogen aldehydes as their dimethylacetal derivatives.

Keywords

• plasmalogens aldehydes
• cyclopropane synthetase
• specificity