Antioxidant activity of palm oil carotenes in peroxyl radical-mediated peroxidation of phosphatidyl choline liposomes.
The antioxidant efficacy of alpha-carotene and comparison with beta-carotene in multilamellar liposomes prepared from egg yolk phosphatidyl choline (EYPC) exposed to the lipid soluble 2,2'-azobis (2,4-dimethyl valeronitrile) (AMVN) was investigated. Lipid peroxidation was measured as thiobarbituric acid reacting substances (TBARS) at 532 nm or as hydroperoxide formation at 234 nm after separation of phosphatidyl choline hydroperoxide (PCOOH) by high-pressure liquid chromatography (HPLC). Lutein and zeaxanthin, the hydroxyl derivatives of alpha- and beta-carotenes, and the chain breaking antioxidant alpha-tocopherol were also included in the study. AMVN being a lipid soluble, non polar azo initiator penetrates into the hydrophobic interior of the phospholipid bilayer, forming peroxyl radicals which peroxidate the phospholipid leading to PCOOH accumulation. All the carotenoids tested at 1 mol% relative to EYPC significantly suppressed the formation of PCOOH compared to control samples. In this system, alpha-carotene retarded PCOOH formation better than beta-carotene. Similarly, lutein was a better antioxidant than is zeaxanthin. But lutein and zeaxanthin were more effective antioxidants than alpha- and beta-carotenes, respectively. After 1 h of incubation of the carotenoid with AMVN, alpha-, beta-carotene, lutein and zeaxanthin limited PCOOH formation by 77%, 68%, 85% and 82%, respectively, while alpha-tocopherol elicited 90% reduction. AMVN incubated with EYPC for 2 h induced the formation of TBARS compared to control (P < 0.001). alpha-Carotene significantly suppressed the TBARS formation by 78% whilst beta-carotene, lutein, zeaxanthin and alpha-tocopherol elicited 60%, 91% and 80% reductions, respectively. Increasing the concentration of the carotenoid > 1 mol% to EYPC did not significantly increase protection of the membrane against free radical attack. Our findings suggest that alpha-carotene is a better antioxidant than is beta-carotene in phosphatidyl choline vesicles. It may, therefore, be useful in limiting free radical mediated peroxidative damage against membrane phospholipids in vivo.
Farombi
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School of Biological Sciences, University of Liverpool, UK. library@kdl.ui.edu.ng
Britton
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D000975:Antioxidants / Q000494:pharmacology*; D002338:Carotenoids / Q000494:pharmacology*; D015227:Lipid Peroxidation / Q000187:drug effects; D008081:Liposomes / Q000378:metabolism*; D000073878:Palm Oil; D010545:Peroxides / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000378:metabolism*; D010938:Plant Oils / Q000494:pharmacology*; D019207:beta Carotene / Q000494:pharmacology
D000975:Antioxidants; D008081:Liposomes; D010545:Peroxides; D010713:Phosphatidylcholines; D010938:Plant Oils; D019207:beta Carotene; C049375:perhydroxyl radical; D002338:Carotenoids; C041635:alpha-carotene; D000073878:Palm Oil