38327-39-8

The invention describes the preparation and use of carotenoid and epi-lutein compositions to treat various ocular diseases.

(Chemical Equation Presented) (3R,3′R,6′R)-Lutein (1) is a major dietary carotenoid that is abundant in most fruits and vegetables commonly consumed in the U.S. and that accumulates in the human plasma, major organs, and ocular tissues. Numerous epidemiol

(3R,3′R,6′R)-Lutein and (3R,3′R)-zeaxanthin are two dietary carotenoids that are present in most fruits and vegetables commonly consumed in the US. These carotenoids accumulate in the human plasma, major organs, and ocular tissues. In the past decade, numerous epidemiological and experimental studies have shown that lutein and zeaxanthin play an important role in the prevention of age-related macular degeneration (AMD) that is the leading cause of blindness in the U.S. and Western World. The invention provides a process for the synthesis of (3R,3′R,6′R)-lutein and its stereoisomers from commercially available (rac)-α-ionone by a C15+C10+C15 coupling strategy. In addition, the present invention also provides access to the precursors of optically active carotenoids with 3-hydroxy-ε-end group that are otherwise difficult to synthesize. The process developed for the synthesis of lutein and its stereoisomers is straightforward and has potential for commercialization.

Circular dichroism (CD) spectroscopy was used to distinguish between the isomeric (all-E)-configured 3′-epilutein (2) and 6′-epilutein (8) to establish the absolute configuration of epilutein samples of different (natural and semisynthetic) origin, including samples of 2 obtained from thermally processed sorrel. Thus, the CD data of lutein (1) and epilutein samples (2) were compared. Our results unambiguously confirmed the (3R,3′S,6′R)- configuration of all epilutein samples. Compound 2 was thoroughly characterized, and its 13C-NMR data are published herewith for the first time.

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.

The application of the Mitsunobu reaction was successfully tested on (3R,3'R)-zeaxanthin, giving the (3S,3'S)-enantiomer and meso form.Applied to natural (3R,3'R,6'R)-lutein, this inversion reaction allowed the preparation of the three other 6'R diastereomers. (3S,3'S,6'R)-lutein with 3',6'-cis-configuration of the ε-ring has not been synthesized before.The observed Cotton effects of the eight lutein diastereomers are rationalized by application of the additivity hypothesis.New trivial names are suggested for the eight lutein isomers on the basis of structural relationships.

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Systematic chromatography has resulted in the isolation of four geometric isomers as products of iodine-catalysed isomerisation of lutein. 13C NMR spectral analysis has established their stereochemistry as mono-cis luteins with a cis-configured double bond at C-9, C-9', C-13 and C-13', respectively.Carbon-13 NMR has also provided unambiguous stereochemical assignment for the previously isolated four mono-cis capsanthins.