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 less than or equal to 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 TEARS, 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 (1.8.5-63.6% inhibition) and stripped-corn oil-in-water emulsion systems (31.7-65.6% inhibition). Hydrogen peroxide (H2O2), hydroxyl radical ((OH)-O-.), 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)-O-. and O-2(.-) was evident. The EPCE scavenged 44-91% of H2O2 in the assay medium after 10 min as compared to 7% reduction in the control.