Mixed Substrates: trans- and «V - [l -14C]Monounsaturated Fatty Acids with a Fairly Uniform Distribution of Positional Isomers

Simple methods are described for the preparation of //-<ms-[l-14C]monounsaturated fatty acids and c is-[l-14C]monounsaturated fatty acids, each with a fairly uniform distribution o f positional isomers, which can serve as mixed substrates in biochemical studies. Methyl trans[ l 14C]octadecenoates and methyl ir<m.s-[l-14C]eicosenoates are prepared by partial catalytic hydrogenation of methyl [1-14C] linolenate and methyl [il-14C] arachidonate, respectively, followed by argentation chromatography of the partially hydrogenated products. Methyl trans[ l 14C]octadecenoates and methyl trans[ l 14C]eicosenoates, thus obtained, yield the corresponding methyl ct's-[l-14C]octadecenoates and methyl c is -[ l 14C]eicosenoates, respectively, after trans-cis equilibration and argen­ tation chromatography. Hydrolysis of each of these methyl esters yields the fatty acids.