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  • Title: A rapid method for separation of plasma low and high density lipoproteins for tocopherol and carotenoid analyses.
    Author: Vogel S, Contois JH, Couch SC, Lammi-Keefe CJ.
    Journal: Lipids; 1996 Apr; 31(4):421-6. PubMed ID: 8743055.
    Abstract:
    Ultracentrifugation (UC) is the method most often employed for separation and quantification of lipoproteins. Because this procedure requires expensive laboratory equipment, a large volume of fresh sample and an inordinate amount of time, it may not be ideal for routine clinical/experimental use. The aim of the current study was to evaluate a method which combines selective precipitation (HDL-P) and immunoseparation (LDL-I) for the rapid and reliable isolation of high density lipoproteins (HDL) and low density lipoproteins (LDL) specifically for vitamin E and carotenoid determination within these fractions. Cholesterol and triacylgylcerol concentrations within the HDL and LDL were also determined to enable expression of vitamin E and carotenoid concentrations per gram of lipid. Isolation of lipoproteins by UC was used as the reference method (HDL-UC/LDL-UC). There were no significant differences between methods for alpha- and gamma-tocopherol in LDL and HDL. Carotenoids measured in HDL and LDL were comparable between the methods. The exception was higher lutein/zeaxanthin concentration in HDL-P and LDL-I compared to HDL-UC and LDL-UC, respectively. Additionally, lycopene concentration was significantly lower in LDL-I compared to LDL-UC. In comparing vitamin E and carotenoid values in lipoproteins separated from fresh and frozen plasma by the direct method, there was no difference in alpha-tocopherol or the majority of carotenoids measured. In conclusion, a combination of selective precipitation and immunoseparation of fresh or frozen plasma for subsequent alpha- and gamma-tocopherol analyses provides an accurate and reliable alternative to lipoprotein separation by UC. Additionally, carotenoid concentrations in HDL separated by selective precipitation and analyses of alpha- and beta-carotenes and beta-cryptoxanthin in LDL separated by immunoseparation are also reliable, while lycopene and lutein/zeaxanthin concentrations in LDL-I are not readily comparable to LDL-UC.
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