| Abstract
| - Although studies have been performed to test whether conjugated linoleic acid (CLA) acts as anantioxidant, the results were not conclusive. In addition, the CLA widely used in previous researchcontains 43% cis-9,trans-11 isomer, 45% trans-10,cis-12 isomer, and 10 other minor isomers. Theobjective of this study was to investigate the antioxidant activity of cis-9,trans-11- and trans-10,cis-12-CLA isomers using high-purity CLA isomers (>98%) by total oxyradical scavenging capacityassay (Winston, G. W.; Regoli, F.; Dugas, Jr., A. J.; Fong, J. H.; Blanchard, K. A. Free Radical Biol.Med.1998, 24, 480−493). At all concentrations (2−200 μM), t10,c12-CLA performed as an antioxidantwith a 15-min lag phase, which was more effective than c9,t11-CLA and α-tocopherol at lowerconcentrations (2 and 20 μM). On the other hand, c9,t11-CLA possessed weak antioxidant activityat 2 and 20 μM, whereas at 200 μM it acted as a strong pro-oxidant, which suggests that discrepanciesof the results of the previous studies on the antioxidant properties of CLA may be due to the balanceof the antioxidant properties of t10,c12-CLA and the pro-oxidant properties of c9,t11-CLA in differentoxidation conditions. Keywords: Conjugated linoleic acid; antioxidant; TOSC assay
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