Abstract

Alkylresorcinols are phenolic lipids present at levels of up to 0.15% of whole grain wheat and rye, but little is known about their presence in food, absorption in animals and humans, and their in vivo biological effects. Because alkylresorcinols are present in the human diet in significant amounts only in products containing whole grain wheat or rye, they have potential to be biomarkers of whole grain wheat and rye intake. This thesis describes some of the research undertaken to investigate whether alkylresorcinols could be biomarkers of whole grain wheat and rye intake. A rapid gas chromatographic method was developed to analyse alkylresorcinols in whole cereal grains. This method was then applied to detect the presence and amount of alkylresorcinols in several cereal grains. Wheat, rye and triticale all contain moderate to high amounts of alkylresorcinols (300-1500 µg/g), while barley contains low amounts (~50 µg/g). In these cereals, alkylresorcinols are present in the bran fraction. All other cereals analysed (rice, oats, maize, sorghum and millet) did not contain any detectable amounts of alkylresorcinols. Previous studies have suggested that alkylresorcinols are destroyed by the baking process. However, an extraction method using hot propanol:water was able to recover all alkylresorcinols from experimental breads, indicating that alkylresorcinols are not destroyed during baking. The absorption of alkylresorcinols in rats, pigs and humans was determined, with values for absorption ranging from 34–79%, depending on the model and the amount of alkylresorcinols consumed. Alkylresorcinols in the plasma of pigs fed a single meal of rye, peaked at 3-4 hours, and remained elevated compared to the baseline levels after 16 hours. Preliminary studies to find alkylresorcinol metabolites in humans suggest that they have their alkyl chains shortened by β-oxidation. The effect of purified rye alkylresorcinols on lipid parameters (tocopherols, cholesterol and fatty acids) was tested on a rat model. Alkylresorcinols did not appear to affect rat performance, but in high amounts they could decrease liver cholesterol, and moderately elevate γ-tocopherol levels. Overall, the results suggest that alkylresorcinols do not have a large effect on lipid absorption/metabolism in rats.