Composition and properties of flaxseed phenolic oligomers

An extract from flaxseed containing oligomeric structures of the phenolic glucosides secoisolariciresinol diglucoside (SDG), p-coumaric acid glucoside and ferulic acid glucoside was fractionated into three oligomeric fractions (F50, F60 and F70) by reversed phase liquid chromatography and further subfractionated by Sepharose CL-6B. The F50 fraction, which had the highest proportion of hydroxycinnamic acid glucosides, was also fractionated on Sephadex LH-20 according to hydrophobicity and size. The different separations resulted in complex profiles of UV-absorbing molecules. HPLC analyses indicated that reversed-phase chromatography separated the oligomers according to composition of the phenolic glucosides, while the subfractionation revealed that other structural features of the oligomers were also important. Using the DPPH radical, SDG and oligomeric fractions showed similar hydrogen-donating abilities comparable to ferulic acid but higher than α-tocopherol, which suggests that SDG was the only active antioxidant.