Profile and distribution of soluble and insoluble phenolics in Chinese rapeseed (Brassica napus)

The profile and distribution of soluble and insoluble phenolics in 10 rapeseed (Brassica napus) varieties were studied in this work. Photometric results show that the soluble total phenolic content (TPC) and the total tannin content (TTC) of rapeseed dehulled flours are much higher than those of rapeseed hulls. Soluble and insoluble phenolics were further analysed by HPLC/MS and MS/MS. For soluble phenolics, seven species were identified and quantified. Sinapine was found to be the major component in both defatted rapeseed hulls and dehulled flours, with its content ranging from 0.93 to 1.76 mg/g and 15.65 to 21.88 mg/g, respectively. For insoluble phenolics, eight phenolic acids were detected in rapeseed hulls, while only two of them were found in their dehulled flours. Sinapic acid and protocatechuic acid, which also were found in dehulled flours, were identified as two major insoluble phenolics in rapeseed hulls. Insoluble TPCs in defatted rapeseed hulls and dehulled flours were shown to be in the similar range.