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Flaxseed has been used for centuries for oil extraction. In recent years it has attracted considerable interest as a result of studies which attribute potential health benefits to its components. Among the compounds that present biological activity, phenolic compounds are of special interest. The dietary lignan secoisolariciresinol diglucoside (SDG) reaches high concentrations in flaxseed. Flaxseed contains also other phenolic compounds, such as phenolic acids. Considering the importance of the phenolic fraction of flaxseed, high performance analytical methods have been developed to characterize its complex phenolic pattern. The understanding of the nature of these compounds is crucial for their possible exploitation in drugs and functional foods.

Changes in the chemical composition and antioxidant activity of flaxseed hull during maturation were investigated. P129 hull variety was studied at four maturation stages (St1, St2, St3, and St4). Significant variation in proximate composition and flaxseed hull oil characteristics were observed. A significant increase in the carbohydrates content of the hull was observed during development. The main methyl esters were linolenic acid (48.95 - 51.52 %), oleic acid (20.27-23.41%) and linoleic acid (15.62-17.70%). The highest polyunsaturated fatty acids (PUFA) were found to be 67.14 % at the first stage of maturity (St1). Flaxseed hull oil was of good quality, containing an abundance of omega-3 essential fatty acids. The iodine value increased, while the saponification value of oil decreased during seed development. The decrease in ascorbic acid content was steady. The maximum level of total phenolic acid content (128.3 mg/100 g oil) was reached at 7 DAF. The antioxidant activity of oilseed was assessed by means of 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging assay. Radical scavenging activity for green hull was 52.74% and mature hull was 69.32%.