Preparation of Fatty Acids Labeled with C14 from Ochromonas danica*

SYNOPSIS. Labeled fatty acids were produced by adding 10 mc acetate‐1,2‐C14 to cultures of Ochrosonas danica, with a recovery of 21.4% of the radioactivity as mixed methyl esters. Individual esters, or mixtures of isomers, were isolated in amounts between 2 and 200 mg by liquid‐liquid chromatography followed by gas‐liquid chromatography. Several esters, including Δ8,11,14‐C20, Δ5,8,11,14,17‐C20, Δ7,10,13,16‐C22 and Δ4,7,10,13,18‐C22 were obtained pure. Linoleate and arachidonate contained not more than 4% isomers; isomerism was more pronounced with C18:3 and C20:2. The effect of different culturing conditions on fatty acid yield, composition and incorporation of C14 was explored. The radioactive level of acids from the preparative run varied within a factor of 3, the average being about 1 μc/mg. All analytical and preparative procedures are described in detail and discussed.