Identification and quantification of phenolic compounds in rapeseed originated lecithin and antioxidant activity evaluation

• Sinapic acid and derivative were identified by 1H NMR, UV, and HPLC in the gum.
• Two extraction approaches were compared for extracting phenolics.
• Phenolic compounds were tracked following the typical lecithin production procedure.
• The extracts showed strong antioxidant activity.
• The rapeseed lecithin contains natural phenolics, distinguishing it from others.

Phenolic compounds may exist in the gum generated from rapeseed oil refining as rapeseed is rich in phenolics. Therefore, this work identified the main phenolic compounds, followed by tracking their flow according to typical lecithin production procedures. Antioxidant activities of the extracts were also investigated to get a clue of the potential oxidative stability of the final products. Column chromatography, UV spectra, 1H NMR, and HPLC were used to separate and identify the phenolic compounds. Sinapic acid was found to be the dominant phenolic while relatively low contents of sinapine and canolol were also identified. Nonpolar solvent aid extraction was better for extracting more sinapine and sinapic acid while direct ethanol extraction gave more canolol. Almost half of the phenolics in dried gum were removed by acetone during deoiling process, leaving only a small amount in deoiled lecithin. Extracts from deoiled lecithin showed the weakest antioxidant activity while the ethanol solubles showed the strongest. This work demonstrated the occurrences of bioactive phenolic compounds in rapeseed originated gum, which may be an advantage of rapeseed lecithin compared with other types of lecithin. This work could also be a reference for rapeseed lecithin production with different contents of bioactive compounds in industry.