Evening primrose meal: a source of natural antioxidants and scavenger of hydrogen peroxide and oxygen-derived free radicals.

Evening primrose meal (EPM: 1% and 2%, w/w) reduced (p </= 0.05) the formation of 2-thiobarbituric acid-reactive substances (TBARS), hexanal, and total volatiles in cooked comminuted pork by 43.6-72.6%. Phenolic compounds in the EPM were extracted under optimum conditions (with 56% acetone at 71 degrees C for 47 min) predicted by a multivariate analysis. The resulting evening primrose crude extract (EPCE) inhibited the bleaching of beta-carotene in a model system. After 2 h of assay, the system containing 200 ppm EPCE [as (+)catechin equivalents] retained 86% of the initial beta-carotene whereas the control retained only 11%. Inhibition of the formation of TBARS, hexanal, and total volatiles in the cooked comminuted pork containing 200 ppm EPCE [as (+)catechin equivalents] ranged from 67. 3% to 97.5%. The EPCE inhibited the formation of conjugated dienes, hexanal, and total volatiles in stripped-bulk corn oil (18.5-63.6% inhibition) and stripped-corn oil-in-water emulsion systems (31.7-65. 6% inhibition). Hydrogen peroxide (H(2)O(2)), hydroxyl radical ((*)OH), and superoxide radical (O(2)(*)(-)) scavenging properties of the EPCE were comparable to those observed for authentic (+)catechin. At 200 ppm of the EPCE [as (+)catechin equivalents], a 100% quenching of (*)OH and O(2)(*)(-) was evident. The EPCE scavenged 44-91% of H(2)O(2) in the assay medium after 10 min as compared to 7% reduction in the control.