Occurrence of trans-Octadec-16-enoic Acid in Sheep and Ox Perinephric Fats

Abstract

IN their investigations on the fatty acid composition of butter-fat, Backderf and Brown¹ deduced the presence of trans-octadec-16-enoic acid, an acid hitherto unknown in Nature. Later this acid was isolated from butter-fat by Hansen and Cooke² and its physical and chemical charac teristics were established. The present communication reports the detection by gas-liquid chromatography of this acid in sheep and ox fats using as a basis for identi fication the gas-liquid chromatographic data previously obtained for the methyl esters of pure trans-octadec-16-enoic acid isolated from butter-fat. The methyl esters of both sheep and ox fats were analysed with a chromatograph fitted with a strontium-90 ioniza-tion detector and an 8 ft. × ¼ in. column. With a ‘Celite’ column impregnated with 20 per cent (w/w) polydiethylene glycol adipate at 207°a peak appeared in both fats with R_F value 1.26 corresponding with that recorded for the methyl ester of trans-octadec-16-enoic acid², but with a ‘Celite’ column containing 5 per cent (w/w) ‘Apiezon L’ at 207° this component was not apparent. As was earlier found with the polydiethylene glycol adipate stationary phase², resolution from other cis and trans C₁₈ isomers and from methyl stearate was complete whereas with a ‘Celite’ column impregnated with 5 per cent (w/w) ‘Apiezon L’ the methyl ester of trans-octadec-16-enoic acid was not separated from methyl stearate. To confirm the presence of trans-octadec-16-enoic acid and other trans acidsin sheep fat and ox fat, work is in progress which is designed to isolate and identify these fatty acid constituents.