Identification of nine acetylenic fatty acids, 9‐hydroxystearic acid and 9,10‐epoxystearic acid in the seed oil ofJodina rhombifolia hook et arn. (Santalaceae)

Abstract

In addition to some usual fatty adds, the seed oil of Jodina rhombifolia (Santalaceae) contains nine acetylenic fatty acids [9-octadecynoic acid (stearolic acid) (1.1%), trans-10heptadecen-8-ynoic acid (pyrulic acid) (20.1%), 7-hydroxytrans-l(~heptadecen-8,ynoic acid (2.3%), trans-10,16-heptadecadien-8-ynoic acid (0.7%), 7-hydroxy-trans-10,16-hepta-decadien~-ynoic acid (0.1%), trans~ll~actadecen-~ynoic acid (ximenynic acid) (20.3%), 8-hydroxy-trans-ll-octadecen-~ ynoic acid (12.2%), trans-ll,17-octadecadien-9-ynoic acid (1.5%), 8-hydroxy-trans-ll,17-octadecadien-9-ynoic acid (1.3%), 9-hydroxystearic acid (<0.1%) and 9,10-epoxystearic acid (0.7%)]. The fatty acids have been analyzed by gas chromatography/mass spectrometry of their methyl ester and 4,4-dimethyloxazoline derivatives. The hydroxy fatty acid methyl esters have been examined also as trlmethyl-sUyl ethers. Furthermore, the fatty acid methyl esters (FAME) have been fractionated according to their polarity (FAMF_~A: nonhydroxy; FAMF~B: hydroxy fatty acids) and to their degree of unsaturation (FAME-A1/A2; FAME-BI/B2) by preparative thin-layer chromatography and argentation chromatography, respectively. All of these fractions have been analyzed by ultraviolet and infrared spectroscopy, and the fractions FAME-A and FAME-B have been analyzed further by nuclear magnetic resonance (1H, 13C, 2D H/C, attached proton test) spectroscopy and gas chromatography/mass spectrometry.KEY WORDS: Acetylenic fatty acids, epoxy fatty acids, gas chromatography/mass spectrometry of 4,4-dimethyloxazoline derivatives of acetylenic fatty acids, hydroxy fatty acids, Jod/na rhombifolia, NMR spectroscopy, Santalaceae.

Biosynthesis and function of polyacetylenes and allied natural products

“…The monoacetylene 5A had been isolated from a single Pyrularia species (Santalaceae) during a survey of the genus [62], as well as Exocarpos cupressiformis [63], and Stericulia foetida [64]. Recent reports have shown it to be more widely distributed at low levels in members of the families Santalaceae (Jodina rhombifolia) [65] and Olacaceae (Ochanostachys amentacea [66]). A preponderance of trans-alkenes is peculiar to compounds derived from 5A, including 5B-K. Leaves of Nanodea muscosa, a Patigonian herb used in folk medicine, contained the atypical acetylenic fatty acids 5L and (13E)-octadecen-11-yneoic acid (5M), with known ene-diynoic acid 5D [67].…”

“…7B, although other hydrogen atom donor/acceptor pairs may be involved including tyrosyl radicals or iron-oxo species. In each of three more recent studies, a variety of more highly unsaturated metabolites presumably derived from stearolate were quantified (e.g., 5J and 5K from J. rhombifolia and 5H, 5I, and 5M from Heisteria sylvanii) [65,69,70].…”

Screening analysis of unknown seed oils

“…Due to the now widely available high-resolution spectrometers, the immense improvement of computer power, and the introduction of new pulse sequences, the technique was recently also applied with great success to mixtures, such as seed oils. [28] 2220 (weak) conjugated diacetylene [65] 958/987 conjugated cis-trans-trans double bonds [65] 1960 allene [15] 955 conjugated acetylenic-trans system [3] 1852/1010 cyclopropene [28] 952/985 conjugated cis-trans-double bonds [65] 1720 α-β unsaturated carboxyl [64] 910 terminal vinyl [3] 1705 chain keto [68] 848/826 epoxy [5] 1235/1370/1050 α-acetoacetates [44] 820 cis-double bond in α-β unsaturated carboxyl [64] …”

“…As only a relatively small number of signals (> 9) can be observed, the information impact of 1 H NMR spectra is limited in comparison with that of 13 C NMR spectra (see 4.2.2). Nevertheless, the detection of a number of functional groups in seed oils, such as allenes [15,69], conjugated double bonds [8,15,70,71], conjugated double-triple bonds [3,10,11,72], cyclopropane [73] and cyclopropene rings [74], cyclopentene [75], epoxy [5], hydroxy [14,76], and terminal vinyl groups [3] is possible by their characteristic 1 H NMR signals. The methylene groups adjacent to a keto group show similar shift values as those adjacent to the carboxyl group when located remote from the carboxyl or other functional groups.…”

“…By a careful interpretation of the coupling patterns and consideration of the integral values of the signals the configuration of the double bonds in conjugated systems can be elucidated even in mixtures [3,8,15,78]. Furthermore, it is possible to distinguish fatty acids that contain a double bond at the n-3 terminal [8,79,80] from other unsaturated fatty acid isomers by means of their terminal methyl signals.…”