Labeling Fatty Acids by Exposure to Tritium Gas. III. Methyl Stearolate and Methyl Linolenate

The 12,13- and 9,10-double bonds of methyl linoleate were found to add tritium in a ratio of 1.4 to 1, respectively. The acetylenic fatty acid ester, methyl stearolate, on exposure to tritium and on subsequent analysis was shown to yield cis- and trans-9,10-tritiooctadecenoate as the major radiochemical product and to give minor amounts of radioactive methyl stearate (saturation) and stearolate (substitution). Radioactivity observed in the C/sub 9/ dibasic and C/ sub 9/ monobasic acids resulted from substitutlon by tritium for the carbon- bonded hydrogen at carbon atoms other than numbers 9 and 10. Radioactivity in the C/sub 9/ mono- and dibasic acids corresponded to the 3 to 4% tritiated methyl stearolate isolated by liquid-liquid chromatography and gas-liquid chromatography before oxidation; radioactive stearic acid corresponded to the 9% tritiated stearic acid similarly isolated by chromatography of the uncleaved fatty acid esters. The octadecatrienoate ester, methyl linolenate, on tritium exposure and oxidative cleavage yielded some radioactive mono- and dibasic acids. Unexpectedly, a comparatively iarge amount of activity (20.3%) was associated with the linolenate peak, indicative of considerable reactlon by substitution. (TCO)