Fatty Acids Profile of Alphitonia neocaledonica and Grevillea exul var. rubiginosa Seed Oils, Occurrence of an ω5 Series

This is the first report of the chemical composition of Alphitonia neocaledonica (AN) and Grevillea exul var. rubiginosa (GER) seed oils. Using retention indices and gas chromatography-mass spectrometry, an unusual family of unsaturated omega 5-fatty acids has been identified. These include 14:1, 16:1, 18:1 and 20:1. Identification of the unsaturated fatty acids was confirmed by formation of DMOX derivatives which gave characteristic and easily interpreted mass spectra. DMDS adducts were used to identify the positions of double bonds in the monounsaturated fatty acids. The major fatty acids were 16:1 omega 5 (45.6%) and 18:1 omega 9 (20.9%) for GER and 18:2 (23.6%) and 18:3 (20.4%) for AN. The total omega 5-monoenes were 63.4 and 21.5% for GER and AN, respectively. The seed oils of AN and GER can be considered as a good source of omega 5-monoenes, especially for GER. The occurrence of the omega 5-monoenes in Alphitonia neocaledonica can at present be considered as an exception within the Rhamnaceae family. Except for Ziziphus jujuba var. inermis, no species of this family has been described with a broad profile of omega 5-monoene fatty acids.