Complex sentence: Flax seed is among the highest sources of lignan (~ 301,129 µg/100 g); the principal lignan precursor found in flaxseed is secoisolariciresinol diglucoside.
Split into simpler sentences: Flax seed is among the highest known sources of lignan. The principal lignan precursor found in flaxseed is secoisolariciresinol diglucoside.