Reinvestigation of the polymethylene‐interrupted 18:2 and 20:2 acids of Ginkgo biloba seed lipids

The fatty acid composition of Ginkgo biloba seed lipids was reinvestigated with particular emphasis on the polymethylene‐interrupted octadecadienoic and eicosadienoic acids. Analysis of the picolinyl esters and 4,4‐dimethyloxazoline derivatives by capillary gas‐liquid chromatography on a highly polar cyanopropyl polysiloxane stationary phase coupled with mass spectrometry revealed the presence of three such acids, with the structures 5,9–18:2, 5,11–18:2, and 5,11–20:2. This indicated that in G. biloba seeds, cis‐vaccenic (11–18:1) acid may be a substrate for the Δ5‐desaturase characteristic of gymnosperms. The 5,11‐18:2 acid was not limited to G. biloba, as it may occur in a few other species. The 5,11‐20:2 acid is a common component of the seed lipids from almost all gymnosperm species analyzed so far.