Both qualitative and quantitative analyses of the major phenolic compounds in barley and flaxseed hulls were conducted using reverse phase high-performance liquid chromatography coupled with photodiode array detection and quadrupole time-of-flight mass spectrometry.
Ferulic acid, p-coumaric acid, vanillic acid and vanillin were identified and quantified in four barley hull samples. Four ferulate dehydrodimers were also detected. The phenolic compounds of flaxseed hull were distinct from those of barley hull. Three flaxseed hull samples varied significantly (P < 0.05) in their contents of secoisolariciresinol diglucoside (16.38-33.92 g kg(-1)), coumaric acid glucoside (35.68-49.22 g kg(-1)) and ferulic acid glucoside (5.07-15.23 g kg(-1)). The phytochemical profiles of co-extracts featured the major phenolic compounds from both barley and flaxseed hulls. The total phenolic content and 2,2-diphenyl-1-picrylhydrazyl radical-scavenging capacity varied significantly (P < 0.05) among different varieties of flaxseed and barley hulls.
As agricultural by-products, barley and flaxseed hulls may be utilised as potential sources of functional food ingredients through extraction and concentration of the phytochemicals identified above.