Preparation of geometrical isomers of linolenic acid

Two methods were developed to prepare important quantities of 18:3Δ9,12,15 geometrical isomers. The first method was based on the isolation of 18:3Δ9 c ,12 c ,15 c from a linseed oil by a combination of urea inclusion and preparative high performance liquid chromatography (HPLC). The isolated 18:3 was isomerized using nitrous acid. The second method was based on the isolation of 18:3Δ9,12,15 geometrical isomers which usually are formed during the heat treatment of vegetable oils. For that purpose a linseed oil was heated at 275 C for 12 hr under nitrogen. The geometrical isomers were isolated using a combination of column chromatography on silicic acid, urea inclusion and preparative HPLC.