The use of supercritical carbon dioxide (SC-CO2) for extracting alkylresocinols from rye bran as investigated. Acetone was also used in extraction for comparative purposes. Better extractions were achieved when SC-CO2 was used with ethanol. In general, the extraction yield was higher the higher the pressure and the temperature above the crossover pressure. When compared to the acetone extract, the use of SCCO2 with ethanol has yielded 80% higher total extracts.

Supercritical fluid extraction (SFE) has received considerable attention is the recent years as an extraction or separation medium for plant material constituents. In particular, supercritical carbon dioxide (SC-CO2) advantages over organic solvent such as less time consuming in sample preparation, easy recovery of the extracts, low toxicity and cost are well documented. The solvent capacity of supercritical carbon dioxide is mainly a function of density and this can easily be changed varying pressure and temperature conditions or adding small amounts of co-solvents. Despite the works developed in the extraction of different plant materials, we could not find so far a single reference on the extraction of alkylresocinols from bran cereals. Alkylresocinols are amphiphilic 1,3-dihydroxybenzene derivatives with an odd-numbered alkyl chain at position 5 of the benzene ring. Derivatives with an odd number and length of 15 to 25 carbon atoms were shown to be common in plants from families Anacardiaceae, Ginkgoaceae or Proteaceae and Gramineae. In food and feed materials, alkylresorcinols occur mostly in some members of the Gramineae family. They are mainly concentrated in the bran of cereal grains, in high levels (>500µg/g) in wheat, rye and triticale and in low amounts in barley, millet and maize. Alkylresorcinols are reported to possess wide range of biological activities like anticancer antimicrobial, antiparasitic, antitumour and some antioxidant effect. Rye alkylresorcinols are characterized by strait hydrocarbon chains with an odd number of carbon atoms attached to position 5 of the phenolic ring. Resorcinols with saturated aliphatic chains represent about 85% (alkylresorcinols), while other resorcinol analogues, including alkylresorcinols with mono- and di-unsaturated aliphatic chains and with keto groups, represent 15%. The consumption of alkylresorcinols by humans, are currently achieved by the intake of whole grain cereals or by incorporation of cereal bran in cereal products. For analytical or biosynthesis studies, these products require previous isolation to make them available. The isolation methods currently employed include extraction with organic solvent; acetone, chloroform or ethyl acetate, especially for analytical purposes. In the present work we employ supercritical carbon dioxide for extracting alkylresorcinols from raw rye rolled flakes.