Online hyphenation of centrifugal partition chromatography with countercurrent chromatography (CPC-CCC) and its application to the separation of saturated alkylresorcinols

Profiling and Isolation of Ten Rare Branched-Chain Alkylresorcinols in Quinoa

Alkylresorcinols (∑ARs) are bioactive lipid compounds predominantly found in cereals. These amphiphilic compounds exist in a high structural diversity and can be divided into two main groups, i.e., 5-alkylresorcinols (ARs) and 2-methyl-5-alkylresorcinols (mARs). The pseudocereal quinoa has a very unique AR profile, consisting not only of straight-chain alkyl chains but also iso- and anteiso-branched isomers. Here, we describe a method for the isolation of such methyl-branched ARs and mARs from quinoa. The enrichment of the ∑AR fraction from the lipid extracts by centrifugal partition chromatography (CPC) was followed by ∑AR profiling using countercurrent chromatography (CCC) and GC/MS analysis of CCC fractions. A total of 112 ∑ARs could be detected, 63 of which had not been previously described in quinoa. Due to this high number of ∑ARs, the direct isolation of individual ARs was not possible using conventional CCC. Instead, the more powerful heart-cut mode was applied to enrich the target compounds. A final purification step-the separation of CCC-co-eluting mARs from ARs -was performed via silver ion chromatography. Altogether, ten rare branched-chain ∑ARs (five iso-branched mARs and five anteiso-branched ARs, including mAR19:0-i and AR20:0-a) were isolated with purities up to 98% in the double-digit mg range.

Isolation of plastochromanol-8 from flaxseed oil by countercurrent separation methods

The naturally occurring antioxidant plastochromanol-8 (PC-8) is a member of the tocochromanol (vitamin E) family which features eight unsaturated isoprene units in the side chain compared to three in the case of γ-tocotrienol. Due to the lack of a commercially available PC-8 standard, we developed a route to gain relevant amounts of highly pure PC-8. Specifically, ∼320 g flaxseed oil was saponified and the bulky PC-8 was enriched by gel permeation chromatography. It followed countercurrent chromatography using the solvent system n-hexane/benzotrifluoride/acetonitrile (20:7:13, v/v/v). The final purification was achieved by centrifugal partition chromatography using the novel solvent system hexamethyldisiloxane/acetonitrile (1:1, v/v). This step provided ∼26 mg PC-8 (>99.5 %, according to HPLC, GC and NMR analysis). Two further, hitherto unknown minor tocochromanols (<1 % of PC-8) were detected and could be identified to be plastochromanol-7 (PC-7) and plastochromanol-9 (PC-9), i.e. tocochromanols with seven and nine unsaturated isoprene units, respectively, in the side chain.

Geometrical and positional isomers of unsaturated furan fatty acids in food

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).

Furan Fatty Acids in Some 20 Fungi Species: Unique Profiles and Quantities

Furan fatty acids (FuFAs) are a group of excellent antioxidants in food. Since data in fungi were scarce, 37 commercial or collected edible and meadow fungi were analyzed on FuFA patterns and contents. FuFA amounts in fresh fungi ranged from not detectable (n = 2) to 40 mg/100 g fungi dry weight. Fresh samples of the popular edible fungi genera Agaricus and Pleurotus showed comparable FuFA contents of 9.0-33 mg/100 g fungi dry weight. The unique FuFA profile of the fungi was dominated by 9-(3,4-dimethyl-5-pentylfuran-2-yl)-nonanoic acid (9D5). In addition, the uncommon 9-(3,4-dimethyl-5-butylfuran-2-yl)-nonanoic acid (9D4) was present in 30% of the samples with contents of up to 0.2 mg/100 g fungi dry weight. Countercurrent separation techniques were used to isolate the main FuFA 9D5, to verify the presence of 9D4, and to determine ultra-traces of 11-(3,4-dimethyl-5-pentylfuran-2-yl)-undecanoic acid (11D5), which may have been assimilated by the fungi from the substrate.