Explain about the Lignans?

Lignans are diphenolic compounds formed by dilnerization of 2 cinnamic acid residues. Most lignans apparently pass through the GIT as fibre. Some lignans may be converted by intestinal microflora to mammalian lignans-enterodiol and enterolactone, which are absorbed through enterohepatic circulation. Flaxseed meal and flour are said to be the richest sources of 2 lignans - Secoisolariciresiizol diglycoside (SDG) and matctiresinol. Other good sources of lignans are pumpkin seeds and sunflower seeds.