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Composition of tomatoes and tomato products in antioxidants (WG1) page 72
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Conclusion for vitamin E
In conclusion, vitamin E is a rather stable lipophilic molecule. It is the main chain-breaking
antioxidant in the process of lipid peroxidation.
8 Antioxidant analysis in foods and biological tissues
Numerous analysis parameters have been shown to influence the extraction yield and
the quantification of tocopherol and carotenoid levels from tomato products and human
biological samples. Such variations could lead to an imprecise estimate of tomato quality or
estimate of association between tomato product consumption and biological responses. So it
is important to choose the most reliable method and this method will depend on the research
objectives.
8.1 Samples
It has been reported that when parallel serum and plasma samples of blood were
collected from one subject, the plasma extract showed 70% and 50% lower retinol and
carotenoid peak heights respectively, as compared with the serum extract (Nierenberg 1984;
Stacewicz-Sapuntzakis et al.1987), suggesting problems with plasma extraction. Because
similar effect was observed for the internal standards, the corrected concentration of these
micronutrients in plasma and serum were in the same range. Additionally, Aebischer et al.
(1999) in a complete quality assurance study have reported that although no differences could
be observed statistically for vitamins and carotenoids, the plasma levels for all analytes were
slightly, but systematically, 2% lower than serum levels.
No degradation of tocopherol or carotenoids was observed during plasma processing
(Gross et al.1995) confirming that plasma samples collected by “typical” clinical blood
collection and processing procedures can be used for carotenoid and tocopherol analysis.
Moreover, the concentrations of carotenoids and tocopherol were similar in samples of
plasma frozen immediately and those that were maintained at room temperature for up to 24 h
collected, then frozen (Craft et al.1988).