Analysis of the seed oil of Heisteria silvanii (Olacaceae)—A rich source of a novel C18 acetylenic fatty acid |
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Authors: | Volker Spitzer Werner Tomberg Rudolf Hartmann Reiner Aichholz |
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Affiliation: | 1. Faculty of Pharmacy, Federal University of Rio Grande do Sul (UFRGS), Curso de Pós-Gradua??o, Avenida Ipiranga, 2752, 90.610.000, Porto Alegre/RS, Brazil 2. Physiologisch-Chemisches Institut, Universit?t Bonn, 53115, Bonn, Germany 3. Novartis Pharma AG, Research, Core Technology Area/Analytics, CH-4002, Basel, Switzerland
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Abstract: | 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-ene acetylenic FA cis-7, trans-11-octadecadiene-9-ynoic acid (heisteric acid) (22.6%)], and 9,10-epoxystearic acid (0.6%) could be identified in the seed
oil of Heisteria silvanii (Olacaceae). Two further conjugated acetylenic FA 9,11-octadecadiynoic acid (0.1%) and 13-octadecene-9,11-diynoic acid (0.4%)]
were identified tentatively by their mass spectra. The FA mixture has been analyzed by gas chromatography/mass spectrometry
(GC/MS) of their methyl ester and 4,4-dimethyloxazoline derivatives. The structure of heisteric acid was elucidated after
isolation via preparative silver ion thin-layer chromatography and by various spectroscopic methods ultraviolet; infrared; 1H, 13C nuclear magnetic resonance (NMR); 1H−1H and 1H−13C correlation spectroscopy]. To determine the position of the conjugated ene-yne-ene system, the NMR spectra were also measured
after addition of the lanthanide shift reagent Resolve-Al EuFODTM. Furthermore, the triyglyceride mixture was 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 for 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 corresponding carboxylate anions RCOO]− of the fatty acids, respectively. 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 TAG containing acetylenic FA showed
an unexpected increase of the retention time in comparison to the TAG containing usual FA, thus making the prediction of the
elution order of lipid samples containing acetylenic FA difficult. |
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