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 a nd eicosadienoic acids. Analysis of the picolinyl esters and 4,4-dimethylox azoline derivatives by capillary gas-liquid chromatography on a highly pola r 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-vacceni c (11-18:1) acid may be a substrate for the Delta 5-desaturase characterist ic of gymnosperms. The 5,11-18:2 acid was not limited to G. biloba, as it m ay occur in a few other species. The 5,11-20:2 acid is a common component o f the seed lipids from almost all gymnosperm species analyzed so far.