Eighteen carotenoids as well as vitamin A and two forms of vitamin E (γ- and α-tocopherol) have been separated from extracts of human plasma by high-performance liquid chromatography (HPLC) on reversed-phase and silica-based nitrile-bonded columns. In the order of chromatographic elution on a C18 reversed-phase column, the carotenoids were identified as (3R,3′R,6′R)-β,ε-carotene-3,3′-dlol [(3R,3′R,6′R)-lutein], (3R,3′R)-β,β-carotene-3,3′-dlol [(3R,3′R)-zeaxanthin], 5,6-dihydroxy-5,6-dihydro-ψ,ψ-carotene,3-hydroxy-2′,3′- didehy-dro-β,ε-carotene,β,ε-caroten-3-ol,3-hydroxy-β- carotene,ψ,ψ-carotene, 7,8-dihydro-ψ,ψ-carotene, β,ψ-carotene, 7,8,7′,8′-tetrahydro-′,′-carotene, β,ε-carotene, β,β-carotene, 7,8,11,12,7′,8′-hexahydro-ψ,ψ-carotene, and 7,8,11,12,7′,8′,-11′,12′-octahydro-ψ,ψ-carotene. The polar carotenoids, which eluted in the vicinity of lutein and were unresolved on the C18 column, have been separated on a nitrile-bonded column employing isocratic HPLC conditions. In the order of elution, the carotenoids were ε,ε-carotene-3,3′-dione, 3′-hydroxy-ε,ε-caroten-3-one, 5,6-dihydroxy-5,6-dihydro-ψ,ψ-carotene, 3-hydroxy-β,ε-caroten-3′-one, (all-E,3r,3′R,6′R)-lutein, (all-E,3R,3′R)-zeaxanthin, and (all-E,3R,3′S,6′R)-β,ε-carotene-3,3′-diol (3′-epilutein) followed by several geometrical isomers of lutein and zeaxanthin.
