Epsilon Open Archive

Abstract

Flaxseed is the richest plant source of the lignan secoisolariciresinol diglucoside (SDG). In flaxseed, SDG exists in an oligomeric structure with 3-hydroxy-3-methyl glutaric acid (HMGA) forming a phenolic complex together with p-coumaric acid and ferulic acid glucosides and herbacetin diglucoside (HDG). Epidemiological and animal studies indicate protective effects of flaxseed and SDG towards hormone-dependent cancers and cardiovascular diseases, and reducing effect toward cholesterol levels in blood. Knowledge about the structural features and properties of the phenolic complex are required to further understand bioavailability, bioconversion and bioactivity of flaxseed lignans in humans and animals, the biosynthesis in flaxseed, as well as if it may affect technology and quality of food products containing flaxseed or the phenolic complex. A new fast and simple high-performance liquid chromatographic (HPLC) method was developed for analysing secoisolariciresinol diglucoside (SDG), p-coumaric acid glucoside and ferulic acid glucoside, based on direct hydrolysis of defatted flaxseed flour using alkali. Variations in SDG, p-coumaric acid glucoside and ferulic acid glucoside content were reported in flaxseed samples and bread products containing flaxseed. The composition and properties of flaxseed phenolic complex were studied by reversed-phase liquid chromatography and gel filtration fractionation. Results indicate that the phenolic glucosides exist in oligomers with variable molecular sizes. A complicated linkage pattern and/or possibly interactions with other components may contribute to the observed complexity. SDG and the phenolic complex showed similar hydrogen-donating abilities to ferulic acid but higher than α-tocopherol in the DPPH inhibition metod, suggesting that SDG was the only active antioxidant in the phenolic complex. Contradicting results were obtained on the effect of SDG on levels of Vitamin E and cholesterol in two rat studies.