Antioxidant and free radical-scavenging properties of ethanolic extracts of defatted borage (Borago ocinalis L.) seeds

Borage meal exerted a concentration-dependent antioxidant activity in a meat model system. At 2% (w/w), it inhibited (p 0.05) 2-thiobarbituric acid-reactive substances (TBARS), hexanal and total volatile formation in meat by 26.5, 30.5 and 18.6%, respectively. Antioxidant compounds in the meal were concentrated at optimum extraction conditions (in 52% ethanol at 74 C for 62 min) predicted by response surface methodology (RSM). The resulting extract inhibited (p40.05) the coupled oxidation of b-carotene and linoleate in a b-carotene-linoleate system. The system containing extract at a level providing 200 ppm phenolics retained 81% of the initial b-carotene after 2 h of assay whereas the control retained only 11%. Inhibition (p40.05) of TBARS, hexanal and total volatile formation in a meat system containing 200 ppm extract ranged from 18.9 to 88.3%, depending upon the concentration being tested. The extract inhibited (p40.05) conjugated diene, hexanal and total volatile formation in bulk corn oil (8.3±49.6% inhibition) and corn-oil-in water emulsion (5.2±32.2% inhibition). Hydrogen peroxide, hydroxyl radical and superoxide radicalscavenging properties of the extract were somewhat less than, but comparable to, those observed for trans-sinapic acid at similar concentrations of phenolics. At 200 ppm, a 100% quenching of the hydroxyl radical and superoxide radical was evident. The extract scavenged 29±75% of the hydrogen peroxide in assay media after 10 min of assay as compared to 3% reduction in the control. # 1999 Elsevier Science Ltd. All rights reserved.