Antioxidant activity of evening primrose phenolics in sunflower and rapeseed oils

Crude ethanol/ethyl acetate extracts of industrial evening primrose (Oenothera biennis L.) seed meal were separated into six fractions using the Sephadex LH‐20 column chromatography and 96% aqueous ethanol as a mobile phase. Their antioxidant activities were tested in sunflower and rapeseed oils by using an Oxidograph apparatus at a temperature of 110 °C. Only the fractions III and IV displayed a pronounced antioxidant activity while the other fractions were either inactive or even pro‐oxidative. The active fractions contained phenolic acids and their esters; gallic acid, methyl and ethyl gallates, protocatechuic acid and its methyl ester were identified by GC/MS. Catechin was present, too, but exhibited only moderate antioxidant activity in sunflower oil.