Preparation of deuterium-labelled linolenic acid for fatty acid metabolism studies

Linolenic acid-d6 (cis-9, cis-12, cis-15-octadecatrienoic-9, 10, 12, 13, 15, 16-d6 acid) was prepared by reduction of its triacetylenic precursor with Lindlar catalyst and deuterium gas. The precursor was prepared by the Grignard coupling of 1-iodo-2,5-octadiyne and 9-decynoic acid. 1-Bromo-2-pentyne (prepared from 2-pentynol by reaction with triphenylphosphine dibromide) was coupled with 2-propynol and converted to the iodide to prepare 1-iodo-2,5-octadiyne while the acetylenic acid was synthesized by coupling 8-bromooctanoic acid and lithium acetylide/ethylenediamine complex. Reverse-phase chromatography (acetonitrile as solvent) was used to purify the d6-acid (overall yield: 11%, 91% d6). Mice were fed both the prepared acid and linolenic acid labelled with deuterium on the non-olefinic carbons. The rates of incorporation and distribution of the acids were evaluated for possible isotope effects caused by the deuterium atoms on the double bonds