Leung Y H, Liu R H
Department of Food Science and Institute of Comparative and Environmental Toxicology, Stocking Hall, Cornell University, Ithaca, New York 14853, USA.
J Agric Food Chem. 2000 Nov;48(11):5469-75. doi: 10.1021/jf991163d.
Although studies have been performed to test whether conjugated linoleic acid (CLA) acts as an antioxidant, the results were not conclusive. In addition, the CLA widely used in previous research contains 43% cis-9,trans-11 isomer, 45% trans-10,cis-12 isomer, and 10 other minor isomers. The objective 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 capacity assay (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 microM), t10, c12-CLA performed as an antioxidant with a 15-min lag phase, which was more effective than c9,t11-CLA and alpha-tocopherol at lower concentrations (2 and 20 microM). On the other hand, c9,t11-CLA possessed weak antioxidant activity at 2 and 20 microM, whereas at 200 microM it acted as a strong pro-oxidant, which suggests that discrepancies of the results of the previous studies on the antioxidant properties of CLA may be due to the balance of the antioxidant properties of t10,c12-CLA and the pro-oxidant properties of c9,t11-CLA in different oxidation conditions.
尽管已经开展了多项研究来测试共轭亚油酸（CLA）是否具有抗氧化作用，但其结果尚无定论。此外，先前研究中广泛使用的CLA含有43%的顺-9，反-11异构体、45%的反-10，顺-12异构体以及其他10种次要异构体。本研究的目的是通过总氧自由基清除能力测定法（Winston, G. W.; Regoli, F.; Dugas, Jr., A. J.; Fong, J. H.; Blanchard, K. A. Free Radical Biol. Med. 1998, 24, 480 - 493），使用高纯度CLA异构体（>98%）来研究顺-9，反-11-和反-10，顺-12-CLA异构体的抗氧化活性。在所有浓度（2 - 200微摩尔）下，反-10，顺-12-CLA表现为具有15分钟延迟期的抗氧化剂，在较低浓度（2和20微摩尔）时比顺-9，反-11-CLA和α-生育酚更有效。另一方面，顺-9，反-11-CLA在2和20微摩尔时具有较弱的抗氧化活性，而在200微摩尔时它作为强促氧化剂起作用，这表明先前关于CLA抗氧化特性研究结果的差异可能是由于在不同氧化条件下反-10，顺-12-CLA的抗氧化特性与顺-9，反-11-CLA的促氧化特性之间的平衡所致。
