Structure and amount of positional isomers of monounsaturated fatty acids in human depot fat

Positional isomers of decenoic, dodecenoic, and tetradecenoic acids of human adipose tissue have been separated by gas-liquid chromatography and their amounts determined by oxidative cleavage. The following acids have been shown to be present: 7-decenoic, 8-decenoic, 9-decenoic, 7-, 8-, and 9-dodecenoic, and 7-, 8-, 9-, and 11-tetradecenoic acids. Among all isomers of the even-numbered acids from C(10) to C(18) the cis-9-isomer predominates. With increasing chain length, however, the content of 9-isomer decreases and the number of isomers increases. No 3- or 5-enoic acids could be detected. The origin and biosynthesis of all isomers are discussed.

Occurrence of positional isomers of octadecenoic and hexadecenoic acids in human depot fat

Positional isomers of hexadecenoic aud octadecenoic acids of human adipose tissue have been separated by gas-liquid chromatography and their amounts determined by oxidative cleavage (MnO(4) and IO(4)). The following isomeric octadecenoic acids were present: 7-octadecenoic acid (0.4%), 8- (1.9%), 9- (73.0%), 10- (2.5%), 11- (19.0%) and 12- (3.2%). The hexadecenoic acids have also been shown to be a mixture of positional isomers, in which the cis-9-isomer predominates. 10-Hexadecenoic and 12-octadecenoic acids could conceivably be precursors of linoleic acid. The following branched fatty acids have also been determined in human depot fat: 13-methyltetradecanoic, 12-methyltetradecanoic, 14-methylpentadecanoic, 14-methylhexadecanoic, and 16-methylheptadecanoic acid. They were present in percentages of 0.02-0.6% and their identification rests solely on comparison of their gas-liquid chromatographic retention times with those of synthetic compounds.