Antioxidant activity of 9-cis compared to all-trans beta-carotene in vitro.
In the present in vitro study we compared the antioxidative efficiency of the 9-cis to that of the all-trans beta-carotene. The 9-cis isomer was isolated from the alga Dunaliella bardawil. The experimental system consisted of 80 mM methyl linoleate, 4 mM azo-bis-2,2'-dimethylvaleronitrile (AMVN) as a free radical generating agent, and 200 microM beta-carotene (synthetic all-trans, 9-cis or a mixture of the 9-cis and all-trans isomers, having a ratio of 2.3). During the incubation at 37 degrees C the mixtures were analyzed for methyl linoleate hydroperoxides, total beta-carotene concentration, and its isomeric composition. The content of 9-cis beta-carotene in the various systems was negatively correlated to the level of the hydroperoxides accumulated, and positively related to the residual beta-carotene amount. The HPLC analysis of the system containing both isomers revealed a continuous decrease in the 9-cis to all-trans isomer ratio. The results suggest that the 9-cis beta-carotene has a higher antioxidant potency than that of the all-trans isomer and, therefore, it protects the methyl linoleate, as well as the all-trans isomer, from oxidation. This isomeric difference might be explained by the higher reactivity of cis, compared to trans, bonds.
Department of Food Engineering and Biotechnology, Technion-Israel Institute of Technology, Haifa.
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Levin
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Mokady
D000975:Antioxidants / Q000302:isolation & purification; D001391:Azo Compounds; D002338:Carotenoids / Q000302:isolation & purification; D002851:Chromatography, High Pressure Liquid; D056890:Eukaryota / Q000737:chemistry; D005609:Free Radicals; D008041:Linoleic Acids; D015227:Lipid Peroxidation; D009570:Nitriles; D013237:Stereoisomerism; D019207:beta Carotene
D000975:Antioxidants; D001391:Azo Compounds; D005609:Free Radicals; D008041:Linoleic Acids; D009570:Nitriles; D019207:beta Carotene; C055792:2,2'-azobis(2,4-dimethylvaleronitrile); C005575:methyl linoleate; D002338:Carotenoids