Gas chromatographic analysis of alkylresorcinols in rye (Secale cereale L) grains

A method was established for fast and easy analysis of 5-n-alkylresorcinols in rye grains, considering effects of milling (intact grains versus flour), extraction solvent (ethyl acetates methanol and acetone), extraction volume per gram of sample (20 and 40ml) and extraction time (3, 6, 18 and 24h). For intact kernels, extraction of 1 g samples with ethyl acetate (40ml, 24h) is recommended. The ease of extraction is consistent with the presence of alkylresorcinols in the outer layers of the kernel and their absence in the endosperm. The extracts were analysed (without further purification or derivatisation) by gas chromatography using methyl behenate (C22:0, fatty acid methyl ester) as internal standard. Alkylresorcinols were identified by gas chromatography/mass spectrometry, and the major homologues were found to contain alkyl chains of C17:0, C19:0, C21:0, C23:0 and C25:0. The methodology was then applied to analyse the alkylresorcinol content in 15 rye cultivars grown at two locations in Sweden. Total alkylresorcinol contents varied within the range 549-1022 μg g^-1, and the average percentages of the different alkylresorcinols were: 17:0, 23%; 19:0, 32%; 21:0, 26%; 23:0, 11%; and 25:0, 8%.