Abstract:

Six binary solvent systems were used to extract industrial high-temperature rapeseed meal (a byproduct of rapeseed oil extraction at a temperature ranging from 110 to 115 ℃ after steaming at 115 ℃), and a mixture of ethanol and 1 mol/L HCl (7:3, V/V) was the selected solvent system for further studies in view of higher extraction efficiency, DPPH radical scavenging activity and ferric reducing antioxidant power (FRAP) as well as environmental friendship. The following studies included comparisons on total polyphenol content, DPPH radical scavenging activity and FRAP value among the extracts from the residues left after oil extraction from rapeseed shell and kernel, solvent extraction-derived rapeseed meal and industrial hightemperature rapeseed meal, HPLC-MS/MS identification of major components of the extract from solvent extraction-derived rapeseed meal and quantification of sinapine and sinapic acid in it. The total polyphenol content, DPPH radical scavenging activity and FRAP value of the extract from the residue left after oil extraction from rapeseed kernel were all approximately 2-fold higher than those of the extract from rapeseed shell with oil extraction and the contents of sinapic acid and sinapine exhibited approximately 2.5- and 1.5-fold increases, respectively. The comparison between solvent extraction-derived rapeseed meal and industrial high-temperature rapeseed meal indicated that during high-temperature oil extraction, total polyphenol content, DPPH radical scavenging activity, FRAP value and the contents of sinapic acid and sinapine decreased by 12.06%, 10.0%, 5.6%, 5.6% and 21.12%, respectively.

Key words: rapeseed, polyphenol, antioxidant activity, HPLC-MS/MS, sinapine, sinapic acid