Hydroxycinnamic acids are ester-linked directly to glucosyl moieties within the lignan macromolecule from flaxseed hulls

Secoisolariciresinol diglucoside (SDG), ester-linked to hydroxy-methyl-glutaric acid, forms the backbone of the lignan macromolecule. Coumaric acid glucoside (CouAG) and ferulic acid (FeA) link directly to the C-6 and C-2 position, respectively, of a glucosyl moiety of SDG. Ferulic acid glucoside is ester-linked to the macromolecule via its carboxyl group.