Scavenging of reactive-oxygen species and DPPH free radicals by extracts of borage and evening primrose meals

Crude extracts of meals of borage and evening primrose were prepared under optimum extraction conditions and were subjected to Sephadex LH-20 column chromatography. Six fractions from each of the crude extracts were obtained and their content of total, hydrophilic and hydrophobic phenolics determined. The crude extracts and their fractions [at 100 and 200 ppm as sinapic acid (for borage) or catechin (for evening primrose) equivalents] were investigated for their reactive-oxygen species- (ROS; H2O2, O2•-, •OH) and 2,2-diphenyl-1-picrylhydrazyl- (DPPH•) scavenging efficacies. Both types of crude extracts and their fractions exerted a concentration-dependent scavenging of ROS and DPPH•. At 200 ppm, borage crude extract and its fractions III, IV and V exhibited a 100% scavenging of H2O2 whereas evening primrose crude extract and its fraction III, at the same concentration, scavenged H2O2 completely. A complete quenching of O2•- was evident for assay media containing 200 ppm borage and evening primrose crude extracts/fractions with the exception of borage fraction V and evening primrose fraction I which showed about 75% quenching. At 200 ppm, borage and evening primrose crude extracts/fractions (except borage fractions I and III) exerted a complete quenching of •OH. Among the borage and evening primrose crude extracts/fractions investigated, only fraction VI of evening primrose, at 200 ppm, was able to completely quench DPPH•.