Four acetylenic fatty acids [ll-octadecen-9-ynoic acid (E) (ximenynic acid), 11-octadecen-9-ynoic acid (Z), 9,Il-octadecadiynoic acid and 13-octadecen-9,ll-diynoic acid (E) (exocarpic acid)] were found in the seed oil of Curupiru &fcmFis (Olacaceae) as minor compounds. The mass spectra of the methyl esters (EI and C1 mode), picoliiyl esters and 4,4-dimethyloxazoline derivatives of these acids are discussed in detail. Furthermore the NMR data of 9,ll-octadecadiynoic acid and 13-octadecen-9,lI-diynoic acid are presented.
I n t r o d u c t i o n
In our previous paper1 about the composition of the seed oil of Curupira tefeeenris, Black n.sp. (Olacaceae) we concluded from the W spectrum the occurrence of approx. 1.2% acetylenic fatty acids but their structures were not identified. Now the eludication of the structure of four conjugated acetylenic fatty acids is described. Futhermore, different derivatization methods which are known to be useful for the mass spectroscopical localization of isolated double and triple bonds of fatty acids are tested for conjugated systems. The results are discussed.
E x p e r i m e n t a l
Material: Fruits of Curupira tgeensis were collected in the region of Tefk (Brazil) in march, 1989. The botanical identification was made in the herbarium of the Museu Goeldi, Belkm (Brazil).
Extraction of oil, preparation of methyl esters and isolation of the diffment FAMEfiactions:
The method of Hara and Radin' with hexaneliso-propanol (2 : 1; v/v) was used for extraction of the total lipids from the seeds. The oil was saponified with 1M KOH/EtOH and the nonsaponifiable compounds were removed by extraction with hexane/diethyl ether (1 : 1; v/v). The saponification mixture was acidified with HCl to pH 1 and the free acids were extracted with hexane, dried over Na$O,, evaporated to dryness and methylated with 2% H,SOJMeOH as described by Christie3. The urea adduct concentration technique was used to enrich the polyunsaturated FAMES of the total lipids3. To increase the enrichment factor the adduct esters were recovered and fractionated once more. Preparative separation of the different methyl ester fractions was carried out by TLC on 0.6 mm silica layers with hexane/diethyl ether (80 : 20 v/v). FAMES were located under W after spraying with 2',7'dichlorofluorescein and recovered by elution with EbO. The solvent was removed by vacuum distillation and the residue was taken up in hexane and stored under nitrogen at -2OOC until use.
Preparation of oxazoline andpicolinyl derivatives:
The FAME fractions, obtained by TLC separation, were saponified with KOH/EtOH and the free acids were extracted with hexane at pH 1. Solvent was removed by vacuum distillation and the fatty acids were converted in 4,4-dimethylox-