Countercurrent chromatographic fractionation followed by gas chromatography/mass spectrometry identification of alkylres
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RESEARCH PAPER
Countercurrent chromatographic fractionation followed by gas chromatography/mass spectrometry identification of alkylresorcinols in rye Tim Hammerschick 1 & Tim Wagner 1 & Walter Vetter 1 Received: 18 August 2020 / Revised: 24 September 2020 / Accepted: 29 September 2020 # The Author(s) 2020
Abstract Alkylresorcinols (5-alkyl-1,3-dihydroxybenzenes, ARs) are bioactive phenolic lipid compounds which are particularly abundant in rye and partly other cereals. In this study on ARs, whole rye grain extracts were gained with cyclohexane/ethyl acetate (46/54, w/w). Silylated extracts were used to develop a gas chromatography with mass spectrometry method in the selected ion monitoring mode (GC/MS-SIM) for the sensitive detection of conventional ARs along with keto-substituted (oxo-AR) and ring-methylated ARs (mAR) with 5-alkyl chain lengths of 14 to 27 carbon atoms and 0 to 4 double bonds in one run. Analysis was performed by countercurrent chromatographic (CCC) fractionation using the solvent system n-hexane/ethyl acetate/methanol/water (9/1/9/1, v/v/v/v). Subsequent GC/MS-(SIM) analysis of 80 silylated CCC fractions enabled the detection of 74 ARs in the sample. The CCC elution of the ARs followed the equivalent chain length (ECL) rule in which one double bond compensated the effect of two (additional) carbon atoms. Novel or rarely reported ARs were detected in virtually all classes, i.e. saturated AR (AR14:0), even-numbered monounsaturated AR isomers (AR16:1-AR26:1), triunsaturated ARs (AR25:3), oxoARs (AR17:0 oxo, AR19:1 oxo, AR21:2 oxo, AR23:2 oxo) and odd-numbered methyl-ARs (mAR15:0-mAR23:0). Positions of the double bonds of monounsaturated ARs and oxo-ARs were determined with the help of dimethyl disulfide (DMDS) derivatives. Keywords Alkylresorcinols . Rye . Countercurrent chromatography . Gas chromatography . Mass spectrometry
Introduction Alkylresorcinols (ARs) are amphiphilic 1,3-dihydroxybenzene (resorcinol) derivatives characterized by a hydrocarbon chain on C-5 of the resorcinol backbone (Fig. 1) [1]. ARs are bioactive molecules, which may display favourable antioxidative, anticancerogenic, antimicrobial and antiparasitic effects [2, 3]. Also, inhibition of some metabolic enzymes has been observed in in vitro assays [4]. The most relevant dietary sources of ARs are rye and other members of the Gramineae family (especially wheat and Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00216-020-02980-3) contains supplementary material, which is available to authorized users. * Walter Vetter [email protected] 1
Department of Food Chemistry (170b), Institute of Food Chemistry, University of Hohenheim, 70599 Stuttgart, Germany
triticale), in which ARs may contribute with more than 500 μg to 1 g of the fresh weight [1]. Specifically, highest AR amounts are found in the outer cuticula [5]. Rye is not only the richest source of ARs but also known for a high variety of AR structures [1]. In the following, these will be discussed by means of s
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