Canola/rapeseed hull phenolics as potential free radical scavengers

Canola/rapeseed hulls contain up to 6% phenolics, including phenolic acids, flavonoids and condensed tannins. Therefore, after dehulling, the hulls may be used as a potential source of natural antioxidants, In this study scavenging effects of crude hull extracts as well as their non-tannin and tannin fractions on alphaalpha-diphenyl-beta-picrylhydrazyl (DPPH) radical were evaluated. Crude extracts of polyphenols were obtained from defatted Cyclone canola and Kolner, Ligaret and Leo rapeseed hulls with 70% acetone. The scavenging effect of crude phenolic extracts, at a dose of I mg, on DPPH radical was 35.2-50.5%. Crude extract of Cyclone canola hull phenolics was further fractionated on a Sephadex LH-20 column affording Five non-tannin and four tannin fractions. The scavenging effect of fractions II and IV, at 1mg, on DPPH radical was 94 and 78.4%, respectively. Fractions 1, 111 and IV showed weak DPPH scavenging effects. The scavenging effects of tannin fractions on DPPH radical were similar to those exhibited by crude polyphenols.