SEARCH · PubMed Health

Results for “Xanthophylls”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8Linked to original sources

PubMed1996

Antioxidant activities of carotenes and xanthophylls.

The purpose of this study was to assess the relative antioxidant activities of a range of carotenes and xanthophylls through the extent of their abilities to scavenge the ABTS(.+) radical cation. The results show that the relative abilities of the carotenoids to scavenge the ABTS(.+) radical cation are influenced by the presence of functional groups with increasing polarities, such as carbonyl and hydroxyl groups, in the terminal rings, as well as by the number of conjugated double bonds.

Antioxidants↗

PubMed1991

A simple model describing the kinetics of the xanthophyll cycle.

A new kinetic model of the xanthophyll cycle is proposed. The model is based on the assumption that the light-dependent interconversion of the so-called available and unavailable violaxanthin constitutes the rate-limiting process of the cycle at intermediate, non-saturating light intensities. This assumption, together with the known properties of violaxanthin de-epoxidase, explains all specific features of the experimental facts.

Carotenoids↗

PubMed2006

A micellar model system for the role of zeaxanthin in the non-photochemical quenching process of photosynthesis--chlorophyll fluorescence quenching by the xanthophylls.

To get an insight to the mechanism of the zeaxanthin-dependent non-photochemical quenching in photosystem II of photosynthesis, we probed the interaction of some xanthophylls with excited chlorophyll-a by trapping both pigments in micelles of triton X-100. Optimal distribution of pigments among micelles was obtained by proper control of the micelle concentration, using formamide in the reaction mixture, which varies the micellar aggregation number over three orders of magnitude. The optimal reaction mixture was obtained around 40% (v/v) formamide in 0.2-0.4% (v/v) triton X-100 in water. Zeaxanthin in the micellar solution exhibited initially absorption and circular dichroism spectral features corresponding to a J-type aggregate. The spectrum was transformed over time (half-time values vary-an average characteristic figure is roughly 20 min) to give features representing an H-type aggregate. The isosbestic point in the series of spectral curves favors the supposition of a rather simple reaction between two pure J and H-types dimeric species. Violaxanthin exhibited immediately stable spectral features corresponding to a mixture of J-type and more predominately H-type dimers. Lutein, neoxanthin and beta-carotene did not show any aggregated spectral forms in micelles. The spectral features in micelles were compared to spectra in aqueous acetone, where the assignment to various aggregated types was established previously. The specific tendency of zeaxanthin to form the J-type dimer (or aggregate) could be important for its function in photosynthesis. The abilities of five carotenoids (zeaxanthin, violaxanthin, lutein, neoxanthin and beta-carotene) to quench chlorophyll-a fluorescence were compared. Zeaxanthin, in its two micellar dimeric forms, and beta-carotene were comparable good quenchers of chlorophyll-a fluorescence. Violaxanthin was a much weaker quencher, if at all. Lutein and neoxanthin rather enhanced the fluorescence. The implications to non-photochemical quenching process in photosynthesis are discussed.

Carotenoids↗

PubMed2003

Interaction of isomeric forms of xanthophyll pigment zeaxanthin with dipalmitoylphosphatidylcholine studied in monomolecular layers.

Two-component monomolecular layers were formed with DPPC and two stereoisomers of zeaxanthin 9-cis and 13-cis at the argon-water interface. Very distinct over-additivity which represents affection of a lipid arrangement in the membrane has been observed in the case of zeaxanthin 9-cis (maximum at 20 mol%) but not in the case of zeaxanthin 13-cis. The differences in the organization of the isomers of zeaxanthin-DPPC monolayers are interpreted in terms of the different orientation of both xanthophylls at the interface observed at relatively high surface pressures (>25 mN/m) comparable to the surface pressures of biomembranes. The results are consistent with the model according to which zeaxanthin 9-cis adopts a vertical orientation at the polar-nonpolar interface in contrast to zeaxanthin 13-cis, which is oriented horizontally owing to the fact that it interacts by two hydroxyl groups with the same hydrophobic-hydrophilic interface in the monolayer. The findings are discussed in comparison with the behavior of zeaxanthin in the conformation all-trans in the same system. Zeaxanthin all-trans forms efficiently molecular aggregates in the mixed monolayers in contrast to cis isomers. Circular dichroism measurements show the formation of molecular structures by zeaxanthin 13-cis that are interpreted as dimers. FTIR measurements show that these dimers are stabilized by van der Waals interactions unlike aggregated structures formed by all-trans zeaxanthin that are stabilized by hydrogen bonding. Physiological importance of the differences in aggregation and orientation of stereoisomers of zeaxanthin in lipid environment is discussed.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed2005

Heat-induced and light-induced isomerization of the xanthophyll pigment zeaxanthin.

Zeaxanthin is a xanthophyll pigment that plays important physiological functions both in the plant and in the animal kingdom. All-trans is a stereochemical conformation of zeaxanthin reported as specific for the thylakoid membranes of the photosynthetic apparatus and the retina of an eye. On the other hand, the pigment is subjected, in natural environment, to the conditions that promote stereochemical isomerization, such as illumination and elevated temperature. In the present work, the light-induced and heat-induced (the temperature range 35-95 degrees C) isomerization of all-trans zeaxanthin in organic solvent environment has been analyzed by means of the HPLC technique. The 13-cis conformation has been identified as a major one among the isomerization products. The activation energy of the all-trans to 13-cis isomerization has been determined as 83 +/- 4 kJ/mol and the activation energy of the back reaction as 30 +/- 7 kJ/mol. The reaction of isomerization of the all-trans zeaxanthin at 25 degrees C was substantially more efficient upon illumination. Four different wavelengths of light have been selected for photo-isomerization experiments: 450, 540, 580 and 670 nm, corresponding to the electronic transitions of zeaxanthin from the ground state to the singlet excited states: 1(1)Bu+,3(1)Ag-,1(1)Bu- and 2(1)Ag-, respectively. The quantum efficiency of the all-trans zeaxanthin isomerization induced by light at different wavelengths: 450, 540, 580 and 670 nm was found to differ considerably and was in the ratio as 1:15:160:29. The sequence of the quantum efficiency values suggests that the carotenoid triplet state 1(3)Bu, populated via the internal conversion from the 1(3)Ag triplet state which is generated by the intersystem crossing from the 1(1)Bu- state may be involved in the light-induced isomerization. A physiological importance of the isomerization of zeaxanthin in the retina of an eye, photosynthetic apparatus and of the pigment active as a blue light photoreceptor in stomata is briefly discussed.

Light↗

PubMed2005

Enhanced alpha-tocopherol quinone levels and xanthophyll cycle de-epoxidation in rosemary plants exposed to water deficit during a Mediterranean winter.

Photosynthesis operates in a constantly shifting balance between efficient capture of solar energy and its rapid dissipation when captured in excess. In an attempt to better understand the role of alpha-tocopherol in plant photoprotection, we examined the changes in alpha-tocopherol quinone (alpha-TQ), in parallel with those of other low-molecular-weight antioxidants, in rosemary plants exposed to water deficit during a Mediterranean winter. Relative leaf water content (RWC) decreased from about 85% to approximately 65% in drought, but plants did not show symptoms of oxidative damage, as indicated by constant Fv/Fm ratios and malondialdehyde (MDA) levels. alpha-TQ was present at concentrations of 20 mmol per 100 mol of chlorophyll, and represented less than 1% of total tocopherol content in non-stressed leaves. Although alpha-tocopherol levels were not significantly altered, alpha-TQ reached up to 36 mmol per 100 mol of chlorophyll under stress (under both high light and after exposure to increasing water deficit at lower light intensities). Furthermore, both alpha-TQ and xanthophyll cycle de-epoxidation were strongly negatively correlated with the relative efficiency of photosystem II photochemistry (phiPSII) at midday. The biological significance of alpha-tocopherol and alpha-TQ in the network of photo- and antioxidative protection mechanisms evolved by plants to withstand stress is discussed.

Antioxidants↗

PubMed2005

Biosynthesis of the xanthophyll plectaniaxanthin as a stress response in the red yeast Dioszegia (Tremellales, Heterobasidiomycetes, Fungi).

Carotenoid biosynthesis was examined in a phylloplane yeast identified by ITS, 18S and 28S rDNA analysis as a Dioszegia sp. close to D. takashimae. In well-aerated flask or fermentor cultures, this strain produced essentially a single pigment confirmed as the xanthophyll plectaniaxanthin by NMR analysis, at concentrations of 103-175 microgg(-1) biomass dry weight. Detailed studies showed increases in plectaniaxanthin concentrations in the presence of 5 mM hydrogen peroxide (1.8-fold), 50 and 100 microM duroquinone (3.1- and 3.7-fold, respectively), and 2% ethanol (4.9-fold). Whereas oxidative stress is known to enhance the biosynthesis of torularhodin or astaxanthin in other red yeasts where they are associated with an antioxidant function, this is the first report implicating plectaniaxanthin in a similar role. At reduced aeration, biosynthesis of plectaniaxanthin was suppressed and its putative precursor gamma-carotene accumulated. The carotenoid cyclase inhibitor nicotine (5-20 mM) inhibited plectaniaxanthin formation, with lycopene accumulating stoichiometrically. Hydroxy groups at C-1' and C-2' therefore seem to be introduced late in plectaniaxanthin biosynthesis, following cyclization of the beta-ionone ring.

Cell Count↗

PubMedDate not supplied

The macular xanthophylls.

The macular pigments are predominantly composed of three carotenoids: lutein, zeaxanthin, and meso-zeaxanthin. These carotenoids are concentrated and distributed in a selective manner. The properties of these pigments are further explored along with their methods of uptake, stabilization, and storage. The dual nature of these pigments as filters and antioxidants are elaborated upon in relation to their protective effects upon the macula, specifically in age-related macular degeneration. Evidence suggests that increased levels of macular pigment are correlated with a decreased risk of age-related macular degeneration. Many have sought to exploit this therapeutic relation. Studies reveal that oral supplementation with lutein and zeaxanthin can increase the levels of macular pigments in the retina and plasma. The effects of such supplementation on actual ocular function have yet to be fully addressed. New and standardized methods of assessing macular pigment density are discussed and future areas of research to further our understanding of macular xanthophylls as they pertain to age-related macular degeneration are highlighted.

Humans↗

PubMed2001

Non-invasive measurement of the concentration of melanin, xanthophyll, and hemoglobin in single fundus layers in vivo by fundus reflectometry.

A new model of the reflection of the human ocular fundus on the basis of the adding-doubling method, an approximate solution of the radiative transport equation, is described. This model enables the calculation of the concentration of xanthophyll in the retina, of melanin in the retinal pigment epithelium and in the choroid, and of hemoglobin in the choroid from fundus reflectance spectra. The concentration values found in 12 healthy subjects are in excellent agreement with literature data. In single cases of pathologic fundus alterations possible benefits to the ophthalmologic diagnostics is demonstrated.

Choroid↗

PubMed2005

Isolation and characterization of a xanthophyll-rich fraction from the thylakoid membrane of Dunaliella salina(green algae).

Long-term acclimation to irradiance stress (HL) of the green alga Dunaliella salina Teod. (UTEX 1644) entails substantial accumulation of zeaxanthin along with a lowering in the relative amount of other pigments, including chlorophylls and several carotenoids. This phenomenon was investigated with wild type and the zea1 mutant of D. salina, grown under conditions of low irradiance (LL), or upon acclimation to irradiance stress (HL). In the wild type, the zeaxanthin to chlorophyll (Zea/Chl)(mol : mol) ratio was as low as 0.009 : 1 under LL and as high as 0.8 : 1 under HL conditions. In the zea1 mutant, which constitutively accumulates zeaxanthin and lacks antheraxanthin, violaxanthin and neoxanthin, the Zea/Chl ratio was 0.15 : 1 in LL and 0.57 : 1 in HL. The divergent Zea/Chl ratios were reflected in the coloration of the cells, which were green under LL and yellow under HL. In LL-grown cells, all carotenoids occurred in structural association with the Chl-protein complexes. This was clearly not the case in the HL-acclimated cells. A beta-carotene-rich fraction occurred as loosely bound to the thylakoid membrane and was readily isolated by flotation following mechanical disruption of D. salina. A zeaxanthin-rich fraction was specifically isolated, upon mild surfactant treatment and differential centrifugation, from the thylakoid membrane of either HL wild type or HL-zea1 mutant. Such differential extraction of beta-carotene and Zea, and their separation from the Chl-proteins, could not be obtained from the LL-grown wild type, although small amounts of Zea could still be differentially extracted from the LL-grown zea1 strain. It is concluded that, in LL-grown D. salina, xanthophylls (including most of Zea in the zea1 strain) are structurally associated with and stabilized by the Chl-proteins in the thylakoid membrane. Under HL-growth conditions, however, zeaxanthin appears to be embedded in the lipid bilayer, or in a domain of the chloroplast thylakoids that can easily be separated from the Chl-proteins upon mild surfactant treatment. In conclusion, this work provides biochemical evidence for the domain localization of accumulated zeaxanthin under irradiance-stress conditions in green algae, and establishes protocols for the differential extraction of this high-value pigment from the green alga D. salina.

Chlorophyta↗

PubMed2002

Kinetics of violaxanthin de-epoxidation by violaxanthin de-epoxidase, a xanthophyll cycle enzyme, is regulated by membrane fluidity in model lipid bilayers.

This paper describes violaxanthin de-epoxidation in model lipid bilayers. Unilamellar egg yolk phosphatidylcholine (PtdCho) vesicles supplemented with monogalactosyldiacylglycerol were found to be a suitable system for studying this reaction. Such a system resembles more the native thylakoid membrane and offers better possibilities for studying kinetics and factors controlling de-epoxidation of violaxanthin than a system composed only ofmonogalactosyldiacylglycerol and is commonly used in xanthophyll cycle studies. The activity of violaxanthin de-epoxidase (VDE) strongly depended on the ratio of monogalactosyldiacylglycerol to PtdCho in liposomes. The mathematical model of violaxanthin de-epoxidation was applied to calculate the probability of violaxanthin to zeaxanthin conversion at different phases of de-epoxidation reactions. Measurements of deepoxidation rate and EPR-spin label study at different temperatures revealed that dynamic properties of the membrane are important factors that might control conversion of violaxanthin to antheraxanthin. A model of the molecular mechanism of violaxanthin de-epoxidation where the reversed hexagonal structures (mainly created by monogalactosyldiacylglycerol) are assumed to be required for violaxanthin conversion to zeaxanthin is proposed. The presence of monogalactosyldiacylglycerol reversed hexagonal phase was detected in the PtdCho/monogalactosyldiacylglycerol liposomes membrane by 31P-NMR studies. The availability of violaxanthin for de-epoxidation is a diffusion-dependent process controlled by membrane fluidity. The significance of the presented results for understanding themechanism of violaxanthin de-epoxidation in native thylakoid membranes is discussed.

Galactolipids↗

PubMed2002

Molecular and global time-resolved analysis of a psbS gene dosage effect on pH- and xanthophyll cycle-dependent nonphotochemical quenching in photosystem II.

Photosynthetic light harvesting in plants is regulated by a pH- and xanthophyll-dependent nonphotochemical quenching process (qE) that dissipates excess absorbed light energy and requires the psbS gene product. An Arabidopsis thaliana mutant, npq4-1, lacks qE because of a deletion of the psbS gene, yet it exhibits a semidominant phenotype. Here it is shown that the semidominance is due to a psbS gene dosage effect. Diploid Arabidopsis plants containing two psbS gene copies (wild-type), one psbS gene (npq4-1/NPQ4 heterozygote), and no psbS gene (npq4-1/npq4-1 homozygote) were compared. Heterozygous plants had 56% of the wild-type psbS mRNA level, 58% of the wild-type PsbS protein level, and 60% of the wild-type level of qE. Global analysis of the chlorophyll a fluorescence lifetime distributions revealed three components in wild-type and heterozygous plants, but only a single long lifetime component in npq4-1. The short lifetime distribution associated with qE was inhibited by more than 40% in heterozygous plants compared with the wild type. Thus, the extent of qE measured as either the fractional intensities of the PSII chlorophyll a fluorescence lifetime distributions or steady state intensities was stoichiometrically related to the amount of PsbS protein.

Arabidopsis Proteins↗

PubMed1999

Responses of the xanthophyll cycle pool and ascorbate-glutathione cycle to ozone stress in two tobacco cultivars.

Plants of Nicotiana tabacum (O3-tolerant cv Bel-B and O3-sensitive cv Bel-W3) were exposed to 150 ppb of ozone for 5 h; the fumigation produced visual injury in mature leaves, particularly in Bel-W3. After O3-treatment the pigments of the xanthophyll cycle pool decreased in both cvs, with a strong reduction in violaxanthin content, while antheraxanthin and zeaxanthin increased slightly. Under these conditions the content of leaf abscisic acid (ABA) markedly increased, particularly in O3-sensitive cv, indicating that the violaxanthin may have been partially converted into ABA. The control plants of Bel-B showed an ascorbic acid content four times greater than Bel-W3 and the ozone treatment did not produce significant differences in the ascorbic acid content and in the redox state. The two tobacco cvs were found to have similar total glutathione content, however the redox state was lower in O3-sensitive cv and decreased after ozone exposure. Ozone fumigation caused an increase in oxidized glutathione, particularly in Bel-W3, associated with a reduced glutathione reductase (GR) activity and a reduced GR protein content.

Ascorbic Acid↗

PubMed1995

Suppression of azoxymethane-induced rat colon carcinogenesis by dietary administration of naturally occurring xanthophylls astaxanthin and canthaxanthin during the postinitiation phase.

The modulating effects of dietary feeding of two xanthophylls, astaxanthin (AX) and canthaxanthin (CX) during the postinitiation phase on colon carcinogenesis initiated with azoxymethane (AOM) were investigated in male F344 rats. Animals were initiated with AOM by weekly s.c. injections of 15 mg/kg body wt for 3 weeks and then they were fed the diets containing AX or CX at concentrations of 100 and 500 p.p.m. for 34 weeks. The others contained the groups of rats treated with AX or CX alone and untreated. At the end of the study (week 37), the incidence and multiplicity of neoplasms (adenoma and adenocarcinoma) in the large intestine of rats initiated with AOM and followed by AX or CX containing diet at a high dose (500 p.p.m.) were significantly smaller than those of rats given AOM alone (P < 0.001). In addition, AX or CX feeding significantly inhibited the development of aberrant crypt foci induced by AOM. Dietary exposure to AX or CX also decreased cell proliferation activity as revealed by measuring 5'-bromodeoxyuridine-labeling index as crypt cells, colonic mucosal ornithine decarboxylase activity and blood polyamine levels. These results indicate that AX and CX are possible chemopreventers for carcinogenesis of colon in addition to urinary bladder and oral cavity and such effects may be partly due to suppression of cell proliferation.

Animals↗

PubMed2002

Possible biologic mechanisms for a protective role of xanthophylls.

This contribution surveys the evidence linking the presence of the two xanthophylls, lutein and zeaxanthin, to a protective role in the macular region of the retina. Although the evidence is still associative in nature, it is biologically plausible, and may be resolved with additional intervention trials.

Aging↗

PubMed2006

Hydrolysis of zeaxanthin esters by carboxyl ester lipase during digestion facilitates micellarization and uptake of the xanthophyll by Caco-2 human intestinal cells.

Zeaxanthin (Zea) and lutein are the only dietary carotenoids that accumulate in the macular region of the retina and lens. It was proposed that these carotenoids protect these tissues against photooxidative damage. Few plant foods are enriched in Zea, and information about the bioavailability of Zea from these foods and its accumulation in ocular tissues is limited. The amounts of free Zea and its mono- and diesters were measured for several plant foods that have relatively high concentrations of this xanthophyll. Wolfberry had the greatest concentration of Zea with a diester that accounts for 95% of the total. Free, mono-, and diesters of Zea were present in orange and red peppers, whereas only Zea monoesters were detected in squash. Zea esters were partially hydrolyzed by carboxyl ester lipase (CEL) during simulated digestion. The efficiency of micellarization was dependent on speciation with combined means of free Zea, Zea monoesters, Zea diesters from the digested foods of 81 +/- 8, 44 +/- 5, and 11 +/- 4%, respectively. When exposed to micelles generated during digestion of the test foods, Zea uptake by Caco-2 cells was proportional to the medium content (11-14%). Free Zea was the most abundant form in Caco-2 cells, although Zea monoesters also were detected (<8 +/- 0.7% vs. free Zea). CEL enhanced Zea uptake from micelles (12.3-fold; P < 0.05) by hydrolyzing Zea esters. After cell uptake, concentrations of free and monoesterified Zea remained relatively stable. These data suggest that dietary Zea esters are hydrolyzed by CEL during the small intestinal phase of digestion and that this conversion enhances Zea bioavailability.

Biological Transport↗

PubMed2003

Role of the reversible xanthophyll cycle in the photosystem II damage and repair cycle in Dunaliella salina.

The Dunaliella salina photosynthetic apparatus organization and function was investigated in wild type (WT) and a mutant (zea1) lacking all beta,beta-epoxycarotenoids derived from zeaxanthin (Z). The zea1 mutant lacked antheraxanthin, violaxanthin, and neoxanthin from its thylakoid membranes but constitutively accumulated Z instead. It also lacked the so-called xanthophyll cycle, which, upon irradiance stress, reversibly converts violaxanthin to Z via a de-epoxidation reaction. Despite the pronounced difference observed in the composition of beta,beta-epoxycarotenoids between WT and zea1, no discernible difference could be observed between the two strains in terms of growth, photosynthesis, organization of the photosynthetic apparatus, photo-acclimation, sensitivity to photodamage, or recovery from photo-inhibition. WT and zea1 were probed for the above parameters over a broad range of growth irradiance and upon light shift experiments (low light to high light shift and vice versa). A constitutive accumulation of Z in the zea1 strain did not affect the acclimation of the photosynthetic apparatus to irradiance, as evidenced by indistinguishable irradiance-dependent adjustments in the chlorophyll antenna size and photosystem content of WT and zea1 strain. In addition, a constitutive accumulation of Z in the zea1 strain did not affect rates of photodamage or the recovery of the photosynthetic apparatus from photo-inhibition. However, Z in the WT accumulated in parallel with the accumulation of photodamaged PSII centers in the chloroplast thylakoids and decayed in tandem with a chloroplast recovery from photo-inhibition. These results suggest a role for Z in the protection of photodamaged and disassembled PSII reaction centers, apparently needed while PSII is in the process of degradation and replacement of the D1/32-kD reaction center protein.

Acclimatization↗

PubMed1995

Analysis of the pigment stoichiometry of pigment-protein complexes from barley (Hordeum vulgare). The xanthophyll cycle intermediates occur mainly in the light-harvesting complexes of photosystem I and photosystem II.

The carotenoid zeaxanthin has been implicated in a nonradiative dissipation of excess excitation energy. To determine its site of action, we have examined the location of zeaxanthin within the thylakoid membrane components. Five pigment-protein complexes were isolated with little loss of pigments: photosystem I (PSI); core complex (CC) I, the core of PSI; CC II, the core of photosystem II (PSII); light-harvesting complex (LHC) IIb, a trimer of the major light-harvesting protein of PSII; and LHC IIa, c, and d, a complex of the monomeric minor light-harvesting proteins of PSII. Zeaxanthin was found predominantly in the LHC complexes. Lesser amounts were present in the CCs possibly because these contained some extraneous LHC polypeptides. The LHC IIb trimer and the monomeric LHC II a, c, and d pigment-proteins from dark-adapted plants each contained, in addition to lutein and neoxanthin, one violaxanthin molecule but little antheraxanthin and no zeaxanthin. Following illumination, each complex had a reduced violaxanthin content, but now more antheraxanthin and zeaxanthin were present. PSI had little or no neoxanthin. The pigment content of LHC I was deduced by subtracting the pigment content of CC I from that of PSI. Our best estimate for the carotenoid content of a LHC IIb trimer from dark-adapted plants is one violaxanthin, two neoxanthins, six luteins, and 0.03 mol of antheraxanthin per mol trimer. The xanthophyll cycle occurs mainly or exclusively within the light-harvesting antennae of both photosystems.

Carotenoids↗