This paper describes a rapid, microprocedure for the simultaneous determination of alpha-tocopherol (vitamin E) and retinol (vitamin A) in plasma, and of alpha-tocopherol alone in red cells since cells do not contain retinol. A total lipid extract from 0.1 ml plasma or 0.125 ml red cells and containing internal standards of alpha-tocopheryl acetate and retinyl acetates is injected onto a high pressure liquid chromatography with a reverse phase column developed with methanol-water. An ultraviolet detector with 280-nm filter is used. The chromatogram is complete in 8 min and the alpha-tocopherol and retinol are quantitated by the peak height ratio method. Comparison of results with both plasma and red cells gave excellent agreement with conventional methods for these vitamins. The procedure should be particularly useful for clinical studies and nutrition surveys.
We determined serial changes in four major plasma carotenoid fractions (alpha-carotene, beta-carotene, lutein/zeaxanthin, and lycopene) in 30 men consuming defined daily doses of carotenoids from foods (broccoli, carrots, or tomato juice) or from purified beta-carotene in capsules (12 or 30 mg) for 6 wk while fed a controlled diet. Compared with baseline, beta-carotene increased in the 30- and 12-mg-capsule and carrot groups whereas alpha-carotene increased in the carrot group and lutein increased in the broccoli group. Lower lutein concentrations in recipients of beta-carotene capsules suggested an interaction between these two carotenoids. Lycopene declined in all groups except the tomato-juice group. Total carotenoid concentration changes only reflected the large increases in beta-carotene concentrations and not the smaller changes observed in other individual carotenoids. Overall, purified beta-carotene produced a greater plasma response than did similar quantities of carotenoids from foods sources. However, some foods increased plasma concentrations of certain carotenoids.
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