Secoisolariciresinol diglucoside (SDG) is an antioxidant phytoestrogen present in flax, sunflower, sesame, and pumpkin seeds. In food, it can be found in commercial breads containing flaxseed. It is a precursor of mammal lignans which are produced in the colon from chemicals in foods. Secoisolariciresinol diglucoside (SDG) is an antioxidant phytoestrogen present in flax, sunflower, sesame, and pumpkin seeds. In food, it can be found in commercial breads containing flaxseed. It is a precursor of mammal lignans which are produced in the colon from chemicals in foods. Secoisolariciresinol diglucoside can be isolated from de-fatted (hexane extraction) flaxseed by extraction of the lignan polymer precursor with a water/acetone mixture, followed by acetone removal and alkaline hydrolysis.