Presence of caffeic acid in flaxseed lignan macromolecule

Abstract

Phenolic compounds were extracted from defatted flaxseeds using ethanol-dioxane (1:1, v/v). The crude extract obtained was purified using Amberlite XAD-16 column chromatography with water and methanol as mobile phases. RP-HPLC and SE-HPLC showed a lignan macromolecule (LM) as a dominant phenolic compound in the purified extract. After the alkaline hydrolysis of LM caffeic acid glucoside (CaAG) was isolated using a semi-preparative HPLC and its structure was confirmed by LC-ESI-MS. In LM of the investigated flaxseed, one molecule of caffeic acid corresponded with five molecules of p-coumaric acid and two molecules of ferulic acid. The presence of caffeic acid in the lignan molecule might be very beneficial due to its high antioxidant activity.

Fig. 1

Chromatograms of (a) RP-HPLC (gradient system) and (b) SE-HPLC separations of lignan macromolecule recorded at 280 nm

Fig. 2

RP-HPLC chromatograms of (a) lignan macromolecule; (b) alkaline hydrolysate and (c) alkaline and acid-hydrolysates of flaxseed lignan macromolecule recorded at 320 nm. The separations were performed using an isocratic elution of acetonitrile-water-acetic acid (10:88:2, v/v/v)

Fig. 3

ESI mass spectrum of CaAG isolated from alkaline hydrolysate of flaxseed lignan macromolecule