ABSTRACT
The free radical scavenging effect of flaxseed was screened by HPLC-DPPH ( 2 , 2-diphenyl-1-picrylhydrazyl-high performance liquid chromatography assay ) and colorimetric DPPH methods. To test the effectiveness of the approach, three Lignans ( secoisolariciresinol diglucoside ( SDG ) , secoisolariciresinol ( SECO) and enterodiol( ED) ) with antioxidative properties were investigated both in monomer and mixture. HPLC conditions were optimized using following methods: Waters XBridge C18 was used as stationary phase, acetonil/H2 O was used as mobile phase and detective wavelength was set at 280 nm. Antioxidant activity of standards was investigated by reaction with or without DPPH radical for 20 min as sample and control, respectively. Both of them were analyzed by high performance liquid chromatography. According to the changes of amount of sample and control, the antioxidant activities of standards were calculated as following order:SDG>SECO>ED. Based on above DPPH-HPLC assay and UPLC-Q-TOF-MS, antioxidants extracted from flaxseed were separated, identified and screened. The radical scavenging activities were in the following order:SDG isomer (5)>SDG (4)>7α-[(β-D-glupyranosyl) oxy]-1-methoxyisolariciresinol (1)>(6R,7R, 8S)-1-methoxyisolariciresinol (2)>herbacetindiglucoside (3). It indicated that the HPLC-DPPH assay could be successfully used for the antioxidant activity screening of complex flaxseed extract.