The alkylresorcinol content and homologue composition in selected Polish rye and wheat cultivars and selected whole-grain cereal products were determined in this study. Cereal grains and whole-grain cereal products were extracted with acetone, whereas bread types were extracted with hot 1-propanol. The average alkylresorcinol content in tested rye (approximately 1100 mg/kg DM) and wheat (approximately 800 mg/kg DM) grains harvested in Poland was within the range previously reported in Swedish and Finnish samples. The total alkylresorcinol content in tested cereal products available on the Polish market varied from very low levels in barley grain-based foods up to 3000 mg/kg DM in wheat bran. The total alkylresorcinol content in 14 bread samples extracted with hot 1-propanol varied from approximately 100 mg/kg DM in whole bread made with honey up to approximately 650 mg/kg DM in whole-rye bread. Calculated ratios of C17:0 to C21:0 homologues, a useful parameter previously used to distinguish between rye and wheat cereals and their derived products, was about 1.2-1.4 in rye products, about 0.2 in wheat products, and varied between 0.2 and 0.6 in cereal-derived products containing a mixture of whole rye and/or wheat. The data set obtained were subsequently compared using cluster and principal component analysis, which allowed the tested cereal products to be classified into two major groups consisting of whole-rye or whole-wheat products, respectively. On the basis of that approach, mixed cereal products containing rye and wheat bran or whole rye and wheat flour were grouped between those two well-defined clusters. Our work not only provides a detailed examination of alkylresorcinols in selected Polish rye and wheat cultivars and selected whole-grain cereal products, but also demonstrates that this type of analysis accompanied by the use of proper statistical algorithms offers an objective way to evaluate the quality of whole-grain rye and/or wheat and their derived products.

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Two general spectrophotometric methods were used to analyze alkylresorcinols and determine their total amounts in rye, wheat and cereal products. Alkylresorcinols were extracted from rye bran with acetone, hydrogenated to obtain a mixture of saturated homologues, subjected to preparative high‐performance liquid chromatography (HPLC) to obtain individual species with the side chain ranging from 15 to 25 carbon atoms, and finally quantified by colorimetric reaction with the diazonium salt Fast Blue B (2‐methoxy‐4‐nitoraniline) and by HPLC. The intensity of the reaction between the same weight amounts of homologues with Fast Blue B decreased in the order C15:0 > C17:0 > C19:0 > C21:0 > C23:0 > C25:0. It was demonstrated that calibration curves based on molecular concentration instead of weight amount of the particular homologues were characterized by the same regression equation and showed an acceptable linearity in the range of 5–30 nmol of homologue in a sample. This confirmed that the colorimetric reaction of alkylresorcinols with Fast Blue B is independent of the length of the aliphatic side chain. Total alkylresorcinols were accordingly determined in cereal grain materials. Two extraction systems (acetone and ethyl acetate) were used. The results of the colorimetric method and those calculated from calibration curves based on the weight amounts of the homologues C15:0 and C19:0 were different. In contrast, the results calculated from the calibration curves based on the mole amounts of the particular homologues were very similar or even identical. PRACTICAL APPLICATIONS The color and intensity of the reaction between alkylresorcinols and the diazonium salt Fast Blue B was independent of the length of the alkyl side chain. This feature could be helpful for the differential determination of the phenolic and resorcinolic lipids present in biological samples. Most cereal material and products contain a mixture of various homologues that is characteristic not only of the source (rye, wheat, triticate, barley), but also of the variety and the growth conditions. Therefore, for accurate calibration curves independent of the composition of homologues, they should be prepared on the basis of the mole fraction of the alkylresorcinols present, similar to the quantitation of phospholipids via phosphorus determination. This procedure will also allow the direct comparison of their amounts in different sources of alkylresorcinols. Nevertheless, simultaneous determination of the homologue composition in the samples is desirable (e.g., by reverse‐phase high‐performance liquid chromatography) as different homologues may have various impacts on the biological activity of alkylresorcinols from cereal products.