Lutein, zeaxanthin, and the macular pigment.

The macular region of the primate retina is yellow in color due to the presence of the macular pigment, composed of two dietary xanthophylls, lutein and zeaxanthin, and another xanthophyll, meso-zeaxanthin. The latter is presumably formed from either lutein or zeaxanthin in the retina. By absorbing blue-light, the macular pigment protects the underlying photoreceptor cell layer from light damage, possibly initiated by the formation of reactive oxygen species during a photosensitized reaction. There is ample epidemiological evidence that the amount of macular pigment is inversely associated with the incidence of age-related macular degeneration, an irreversible process that is the major cause of blindness in the elderly. The macular pigment can be increased in primates by either increasing the intake of foods that are rich in lutein and zeaxanthin, such as dark-green leafy vegetables, or by supplementation with lutein or zeaxanthin. Although increasing the intake of lutein or zeaxanthin might prove to be protective against the development of age-related macular degeneration, a causative relationship has yet to be experimentally demonstrated.

Biologic mechanisms of the protective role of lutein and zeaxanthin in the eye.

Thirty-four carotenoids, including 13 geometrical isomers and eight metabolites, in breast milk and serum of three lactating mothers have been separated, identified, quantified, and compared by high-performance liquid chromatography (HPLC)−photodiode array (PDA) detection−mass spectrometry (MS). Among the metabolites were two oxidation products of lycopene and four of lutein/zeaxanthin. In addition, two metabolites of lutein, formed as a result of dehydration of this dihydroxycarotenoid under acidic conditions similar to those of the stomach, have also been identified in plasma and breast milk. The oxidative metabolites of lycopene with a novel five-membered-ring end group have been identified as epimeric 2,6-cyclolycopene-1,5-diols by comparison of their HPLC−UV/visible−MS profiles with those of fully characterized (1H- and 13C-NMR spectroscopy) synthetic compounds. The HPLC procedures employed also detected vitamin A, two forms of vitamin E (γ- and α-tocopherol), and two non-carotenoid food components, ...

Identification, Quantification, and Relative Concentrations of Carotenoids and Their Metabolites in Human Milk and Serum

Part 1 Antioxidants and food stability: The development of oxidative rancidity in foods Inhibiting oxidation Measuring antioxidant activity. Part 2 Antioxidants and health: Cardiovascular disease and nutritional phenolics Antioxidants and anti-tumour properties Predicting the bioavailability of antioxidants in food: the case of carotenoids. Part 3 Natural antioxidants: Introducing natural antioxidants Sources of natural antioxidants: oilseeds, nuts, cereals, legumes, animal products and microbial sources Sources of natural antioxidants: vegetables, fruits, herbs, spices and teas. Part 4 Practical applications: Regulation of antioxidants in food Use of natural antioxidants in food products Preparation of natural antioxidants Natural antioxidant functionality during food processing.

Antioxidants in food : practical applications

Crocin, safranal and picrocrocin from saffron (Crocus sativus L.) inhibit the growth of human cancer cells in vitro

The CD. spectra of carotenoids in the 220-500 nm region may by inspection be classified as (a) essentially Conservative, (b) intermediate, or (c) essentially nonconservative. A conservative spectrum shows in that spectral region a sequence of 5-6 relatively sharp Cotton effects of alternating sign, the rotatory strengths of which roughly add to zero. In a non-conservative spectrum Δϵ has the same sign over the whole region and its absolute value is in general somewhat smaller. In general, typical conservative spectra invert upon isomerization of the molecule from all-trans to mono-cis. Non-conservative spectra do not invert. The model of a chiral polyene of the length of the conjugated carotene chromophore reproduces well the main features of the conservative spectra. The theoretical predictions and the experimental data are shown to conform to the C2-rule [43] [44]. The particular nature of the longest-wavelength transition is interpreted. Based on a summary of the chiroptic data on about 50 naturally occurring compounds, the question is discussed of when conservative spectra arise and when not.

Classification of the CD. Spectra of carotenoids

Aufgrund von Abbauresultaten an naturlichem (+)-Xanthophyll (Lutein) und Xanthophyllathern und eingehender NMR.-Analyse (insbesondere am Abbau-Ionon V), Synthesen und chiroptischen Korrelationen wird bewiesen, dass (+)-Xanthophyll (3R:3′R:6′R)-Chiralitat hat. Fruher gemachte Vorschlage anderer Autoren sind zu korrigieren.



Reduktion von Xanthophyll mit LiAlH4/AlCl3 gibt 3-(R)-Hydroxy-3′,4′-dehydro-6(ξ)-β,γ-carotin. Mit 1-Phenyl-5-chlortetrazol(Base) tritt Wasserabspaltung im β-Ring zu 3,4-Dehydro-6′-(R)-3′-(R)-hydroxy-β-carotin ein.



Die nun bekannte Chiralitat von (+)-Zeaxanthin ((3R:3′R)-Dihydroxy-β,β-carotin) und von (+)-Xanthophyll ((3R:3′R)-Dihydroxy-β,ϵ-carotin) schliesst eine biologische Interconversion aus: sie wurde meso-Zeaxanthin ((3R:3′S)-Dihydroxy-β,β-carotin) ergeben.



Es wird eine Hypothese fur die Hydroxylierung von - bzw. α-Carotin aufgestellt.

Absolute Konfiguration von Xanthophyll (Lutein)

By chemical correlation with manool and ambrein the absolute configurations of the enantiomeric α-cyclogeranic acids, α-cyclogeranials, α-ionones and α- and ϵ-carotenes have been elucidated.

Absolute Konfiguration der enantiomeren α-CyclogeraniumsäUren, α-Cyclogeraniale, α-Jonone, γ-Jonone, α-und ϵ-Carotine

Die im Titel genannten enantiomeren Verbindungen sind durch chemische Reaktionen mit Ambrein und Manool verknupft worden, so dass ihre Chiralitat festgelegt ist. Damit ist zum erstenmal die Konfiguration eines chiralen Carotinoidkohlenwasserstoffes bestimmt. Das naturlich vorkommende (+)-α-Jonon hat R-Konfiguration, ebenso das naturliche (+)-α-Carotin.

Bestimmung der Chiralität der enantiomeren α-Cyclogeraniumsäuren, α-Cyclogeraniale, α-Jonone, γ-Jonone, α-Carotine, ε-Carotine und verwandter Verbindungen durch chemische Verknüpfungsreaktionen. Vorläufige Mitteilung†

Carotenoids from Hips of Rosa pomifera: Discovery of (5Z)-Neurosporene; Synthesis of (3R, 15Z)-Rubixanthin

Extensive chromatographic separations of the mixture of carotenoids from ripe hips of R. pomifera have led to the identification of 43 individual compounds, namely (Scheme 2): (15 Z)-phytoene (1), (15 Z)-phytofluene (2), all-(E)-phytofluene (2a), ξ-carotene (3), two mono-(Z)-ξ-carotenes (3a and 3b), (6 R)-ϵ, ψ-carotene (4), a mono-(Z)-ϵ, ψ-carotene (4a), β, ψ-carotene (5), a mono-(Z)-β, ψ-carotene (5a), neurosporene (6), (5 Z)-neurosporene (6a), a mono-(Z)-neurosporene (6b), lycopene (7), five (Z)-lycopenes (7a–7e), β, β-carotene (8), two mono-(Z)-β, β-carotenes (probably (9 Z)-β, β-carotene (8a) and (13 Z)-β, β-carotene (8b)), β-cryptoxanthin (9), three (Z)-β-cryptoxanthins (9a–9c), rubixanthin (10), (5′ Z)-rubixanthin (=gazaniaxanthin; 10a), (9′ Z)-rubixanthin (10b), (13′ Z)- and (13 Z)-rubixanthin (10c and 10d, resp.), (5′ Z, 13′ Z)- or (5′ Z, 13 Z)-rubixanthin (10e), lutein (11), zeaxanthin (12), (13 Z)-zeaxanthin (12b), a mono-(Z)-zeaxanthin (probably (9 Z)-zeaxanthin (12a)), (8 R)-mutatoxanthin (13), (8 S)-mutatoxanthin (14), neoxanthin (15), (8′ R)-neochrome (16), (8′ S)-neochrome (17), a tetrahydroxycarotenoid (18?), a tetrahydroxy-epoxy-carotenoid (19?), and a trihydroxycarotenoid of unknown structure.

Rubixanthin (10) and (5′ Z)-rubixanthin (10a) can easily be distinguished by HPLC. separation and CD. spectra at low temperature. The synthesis of (3 R, 15 Z)-rubixanthin (29) is described.

The isolation of (5 Z)-neurosporene (6a) supports the hypothesis that the ϵ-end group arises by enzymatic cyclization of precursors having a (5 Z)- or (5′ Z)-configuration.

Richard Buchecker

Papers

Classification of the CD. Spectra of carotenoids

Absolute Konfiguration von Xanthophyll (Lutein)

Absolute Konfiguration der enantiomeren α-CyclogeraniumsäUren, α-Cyclogeraniale, α-Jonone, γ-Jonone, α-und ϵ-Carotine

Bestimmung der Chiralität der enantiomeren α-Cyclogeraniumsäuren, α-Cyclogeraniale, α-Jonone, γ-Jonone, α-Carotine, ε-Carotine und verwandter Verbindungen durch chemische Verknüpfungsreaktionen. Vorläufige Mitteilung†

Das Carotinoidspektrum der Hagebutten von Rosa pomifera: Nachweis von (5Z)‐Neurosporin; Synthese von (3R, 15Z)‐Rubixanthin