ANALYSIS OF THE SEED OIL OF HEISTERIA-SILVANII (OLACACEAE) - A RICH SOURCE OF A NOVEL C-18 ACETYLENIC FATTY-ACID

Besides some usual fatty acids (FA), two conjugated ene-yne acetylenic FA [trans-10-heptadecen-8-ynoic acid (pyrulic acid) (7.4%), and trans -11-octadecen-9-ynoic acid (ximenynic acid) (3.5%)], a novel ene-yne-e ne acetylenic FA [cis-7, trans-11-octadecadiene-9-ynoic acid (heisteri c acid) (22.6%)], and 9,10-epoxystearic acid (0.6%) could be identifie d in the seed oil of Heisteria silvanii (Olacaceae). Two further conju gated acetylenic FA [9,11-octadecadiynoic acid (0.1%) and 13-octadecen e-9,11-diynoic acid (0.4%)] were identified tentatively by their mass spectra. The FA mixture has been analyzed by gas chromatography/mass s pectrometry (GC/MS) of their methyl ester and 4,4-dimethyloxazoline de rivatives. The structure of heisteric acid was elucidated after isolat ion via preparative silver ion thin-layer chromatography and by variou s spectroscopic methods [ultraviolet,. infrared; H-1, C-13 nuclear mag netic resonance (NMR); H-1-H-1 and H-1-C-13 correlation spectroscopy]. To determine the position of the conjugated ene-yne-ene system, the N MR spectra were also measured after addition of the lanthanide shift r eagent Resolve-Al EuFOD(TM). Furthermore, the triyglyceride mixture wa s analyzed by high-temperature GC and high-temperature GC coupled with negative chemical ionization MS. A glass capillary column coated with a methoxy-terminated 50%-diphenyl-50%-dimethylpolysiloxane was used f or the separation of the triacylglycerol (TAG) species. No evidence of decomposition of the TAG species containing conjugated ene-yne-ene FA was observed. Twenty-six species of the separated TAG were identified by means of their abundant quasi molecular ion [M-H](-) and their cor responding carboxylate anions [RCOO](-) of the fatty acids, respective ly. The major molecular species of the TAG were found to be 16:0/18:1/ 18:1, 16:0/18:1/18:3 (heisteric acid), 17:2 (pyrulic acid)/18:1/18:1, 18:1/18:1/18:3 (heisteric acid). The TAC containing acetylenic FA show ed an unexpected increase of the retention time in comparison to the T AG containing usual FA, thus making the prediction of the elution orde r of lipid samples containing acetylenic FA difficult.