Institut für Lebensmittelchemie

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Geometrical and positional isomers of unsaturated furan fatty acids in food
(2022) Müller, Franziska; Hammerschick, Tim; Vetter, Walter
Furan fatty acids (FuFA) are important antioxidants found in low concentrations in many types of food. In addition to conventional FuFA which normally feature saturated carboxyalkyl and alkyl chains, a few previous studies indicated the FuFA co‐occurrence of low shares of unsaturated furan fatty acids (uFuFA). For their detailed analysis, the potential uFuFA were enriched by centrifugal partition chromatography (CPC) or countercurrent chromatography (CCC) followed by silver ion chromatography from a 4,7,10,13,16,19‐docosahexaenoic acid ethyl ester oil, a 5,8,11,14,17‐eicosapentaenoic acid ethyl ester oil and a latex glove extract. Subsequent gas chromatography with mass spectrometry (GC/MS) analysis enabled the detection of 16 individual uFuFA isomers with a double bond in conjugation with the central furan moiety. In either case, four instead of two uFuFA isomers previously reported in food, respectively, were detected by GC/MS. These isomers showed characteristic elution and abundance patterns in GC/MS chromatograms which indicated the presence of two pairs of cis/trans‐isomers (geometrical isomers).
LC‐Orbitrap‐HRMS determination of two novel plastochromanol homologues
(2023) Hammerschick, Tim; Graf, Jana; Vetter, Walter
Scope: The antioxidant plastochromanol-8 (PC-8) is a tocochromanol which differs from γ-tocotrienol in having an unsaturated side chain of eight instead of three isoprene units. The recent isolation of PC-8 from flaxseed oil indicates the additional presence of lower shares of two previously unknown homologues, plastochromanol-7 (PC-7) and plastochromanol-9 (PC-9), which feature seven and nine isoprenoid units respectively on the γ-chromanol backbone. Here, a fast LC-Orbitrap-HRMS method is applied for the determination of PC-7 and PC-9 in seven plant oils and a plant extract. Methods and results: The presence of PC-7, PC-8, and PC-9 is confirmed in all eight investigated samples by LC-Orbitrap-HRMS analysis after saponification. PC-8 amounts of ≈315–350 mg kg−1 in two flaxseed oils, ≈75 mg kg−1 in rapeseed oil, ≈38 mg kg−1 in camelina oil, ≈80–120 mg kg−1 in two mustard oils, ≈90 mg kg−1 in candle nut oil, and ≈900 mg kg−1 dry weight in Cecropia leaves are determined by quantification. Semi-quantification of PC-7 and PC-9 indicated the presence of ≈0.1–1% of PC-7 and PC-9 in varied relative ratios. Conclusion: The novel plastochromanol homologues are of particular interest to researchers with focus on vitamin E and other tocochromanols because of their unexplored bioactivity.
Silver ion chromatography enables the separation of 2‐methylalkylresorcinols from alkylresorcinols
(2023) Hammerschick, Tim; Vetter, Walter
Alkylresorcinols (∑ARs) is the generic term for a highly varied class of lipids found mainly in cereals. These bioactive compounds consist mainly of 5‐alkylresorcinols (ARs), which differ in length, unsaturation, and substituents on the alkyl side chain on C‐5. In addition, 2‐methyl‐5‐alkylresorcinols (mARs) are scarcely studied minor compounds that are supposed to exist with the same structural diversity. In the first step, ∑ARs were enriched by solid‐phase extraction from wheat grain and quinoa seed extracts. The subsequent application of silver ion chromatography (SIC), silica gel, coated with 20% AgNO3, then deactivated with 1% water) enabled an unprecedented full separation of saturated mARs from conventional ARs. Specifically, saturated mARs were eluted with n‐hexane/ethyl acetate (92:8, v/v), and conventional ARs with n‐hexane/ethyl acetate (80:20, v/v). The unpreceded separation indicated that the SIC method could be useful not only for separations according to the degree of unsaturation, but also in the case of steric hindrance by additional (alkyl) substituents. Continued fractionation enabled the collection of unsaturated ARs in wheat and quinoa extracts. In this way, 35 ∑ARs (including five mARs) were detected by gas chromatography/mass spectrometry analysis in wheat and 45 ∑ARs (including 21 mARs) in quinoa. These included several low abundant and partly unknown ∑ARs such as 1,3‐dihydroxy‐5‐tricosadienylbenzene.

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