Distribution of Cyclolinopeptides in Flaxseed Fractions and Products

Hydrophobic cyclic peptides, termed cyclolinopeptides, found in flaxseed are known for their immunosuppressive activity. This study is the first report of the occurrence of cyclolinopeptides in flaxseed fractions and products produced by aqueous processing and cold pressing. The distribution of cyclolinopeptides in flaxseed was determined after processing of flaxseed by various industrial and laboratory processes. Extracts of the water-soluble mucilage did not contain cyclolinopeptides. The cotyledon had the highest concentration of cyclolinopeptides, whereas seed coat had lower levels. An oil body fraction separated from seed after homogenization in water, followed by centrifugation, had the highest concentration of
cyclolinopeptides of the fractions produced by this method. Further washing of the oil body fraction led to a loss of cyclolinopeptides. When oilseed was extruded using an expeller press, cyclolinopeptides were found in greater concentrations in crude oil and the solid sediment present in the oil fraction than in meal or the unprocessed seed. The concentration of cyclolinopeptides in crude flaxseed oil immediately after pressing was much higher than that observed in flaxseed oils purchased from a retail outlet. The effect of oil refining treatments on the removal of cyclolinopeptides was also tested. Acid degumming using aqueous H3PO4 removed cyclolinopeptides from crude flaxseed oil. Alkali refining was less effective as this treatment failed to remove all peptides equally. This work illustrates ways that cyclolinopeptides may be extracted from flaxseed oil that could be developed for large-scale industrial extraction. The ability to extract cyclolinopeptides on a larger scale would allow faster exploitation of commercial applications of these molecules and provide the flaxseed industry with value-added coproducts. (Authors abstract)

Flaxseed oil contains cyclic hydrophobic peptides, known as cyclolinopeptides, that are composed of eight or nine amino acid residues. They have known bioactivity with immunosuppressive and anticancer effects. Flaxseed oil is an excellent commercial source of cyclolinopeptides as these compounds are hydrophobic and are dissolved in oil after seed processing. The present research was directed to the determination of (1) the cyclolinopeptide distribution in flaxseed fractions including seed coat, cotyledon, and oil bodies; (2) the distribution in flaxseed during cold pressing and subsequent oil sedimentation and filtration; (3) the comparative levels of cyclolinopeptides in commercial flaxseed oils; and (4) the effects of acid degumming and alkali refining on the levels of cyclolinopeptides in pressed flaxseed oil. Three procedures were used to process flaxseed in this study. The first method of processing seed was a noncommercial separation of seed into fractions representing gross anatomical structures. In this process seed was first degummed using water, and then gums, seed coats, and seeds were separated, dried, and extracted with acetone. This process provided information on the possible location of the peptides in the plant tissues. In a second process that emulated an existing commercial process, oil bodies were isolated from whole flaxseed following seed hydration. A third process involved a more conventional cold pressing of the seed with a small expeller press. Oil extracted by pressing was subsequently refined, and the fate of the peptides during oil refining was followed. Flaxseed used in this trial had a total cyclolinopeptide concentration of 268.3 micro g/g. It was observed that the majority of cyclolinopeptides were found in flaxseed oil after conventional processing and indicates the possibility that the peptides were stored in oil bodies or oleosomes, the main oil-bearing structures in flaxseed. It is possible that cyclolinopeptides were stored in oil bodies along with triacylglycerols before processing and removed from oil bodies by homogenization and centrifugation, but further confirmation of this is not possible at this time. The levels of cyclolinopeptides varied among five brands of flaxseed oil obtained from a retail outlet. All retail samples had lower peptide levels than flaxseed oil prepared in the laboratory, where 1 (454.0 micro g/g), 2 (90.5 micro g/g), 3 (358.3 micro g/g), 4 (214.1 micro g/g), 5 (445.5 micro g/g), 6 (82.4 micro g/g), and7 (249.7 micro g/g) were found. The lower levels observed in some commercial products might have been caused by additional processing of the commercial products such as acid degumming and alkali refining. The presence of cyclolinopeptides in flaxseed ensures that cyclolinopeptides will also be found in flax-related food products (flaxseed oil, flaxseed  meal, flaxseed bread). The ability to extract cyclolinopeptides at a larger scale would allow faster exploration of the potential applications of these molecules and provide the flaxseed industry with potential value-added coproducts. (Editors comments)