Polymeric fractions containing phenol glucosides in flaxseed

Extract rich in phenolic compounds was obtained from flaxseed with 1,4-dioxane:ethanol (1:1, v/v). This extract (whole polymer) was fractionated by solid-phase extraction into three “polymeric” fractions of comparable polarity. HPLC analyses of the base hydrolysates of the three polymeric fractions showed that they contain the same UV-absorbing components, though at different levels and all contained substantial amounts of a lignan, secoisolariciresinoldiglucoside (SDG). Fractionation of the base hydrolysates by column chromatography, followed by high performance liquid chromatography (HPLC) yielded two pure hydroxycinnamic acid derivatives; 4-O-β-d-glucopyranosyl-p-coumaric acid and 4-O-β-d-glucopyranosylferulic acid, whose structures were identified by nuclear magnetic resonance spectroscopy (NMR). NMR analysis showed all three polymeric fractions to have phenolic and aliphatic components and, in line with HPLC, suggested some structural variations between these fractions. The results of this study suggest that the glucosylated phenolic compounds of flaxseed exist in polymeric structure(s) containing ester linkages.