Role Of Carotenoids Research Articles

Excited states of carotenoid in LH2: an ab initio study

In order to understand the origin of ultrafast carotenoid bandshifts upon photoexcitation of bacteriochlorophyll (BChl) molecules in antenna complexes of photosynthetic purple bacteria, we have performed sa-CASSCF(8,7)/6-31G (and 6-31G*) calculations for the low-lying excited states of the carotenoid rhodopin glucoside (RG). The LH2 environment was simulated via atomic point charges to represent the electrostatic field of the ground and the Q y excited states of BChls near the carotenoid. The calculations showed that excitation of the B800 BChls yields a significant blue-shift of the carotenoid S 2 energy in good agreement with experiments. We also found that the lowest triplet state energy of the RG is below 0.78 eV, which is lower than the energy of 1 O 2 * (0.97 eV), in accord with the role of carotenoids as photoprotectors.

The significance of carotenoids and tocopherols in photoprotection of seven epiphytic fern species of a Mexican cloud forest

Epiphytes experience frequent and rapid changes in water availability andlight intensity. The role of carotenoids and tocopherols in photoprotection ofseven fern species (Asplenium cuspidatum Lam.,Phlebodium areolatum (HB ex Willd.) Smith,Polypodium puberulum Schl. & Cham.,Po. plebeium Schl. & Cham.,Elaphoglossum glaucum Moode,E. petiolatum (Sw.) Urb., andPleopeltis mexicana (Fée) Mickel & Beitel)with different adaptations against drought were investigated. The plants weresampled dark adapted (treatment I), and after light exposure with thesubstrate present (treatment II), with the substrate removed (treatment III)and with substrate and rhizomes removed (treatment IV) to induce increasing degrees of drought stress. The degree of dehydration reached does not resultin permanent damage and was also observed in the field. While none of thetreatments induced significant chlorophyll (chl) degradation, all plantsshowed strong de-epoxidation of the xanthophyll cycle on light exposure (up toa de-epoxidation state of 70%), but without an additional effect ofdesiccation. Most species showed a rapid increase (within hours) ofcarotenoids (mainly β-carotene and lutein) and α-tocopherol onexposure. In A. cuspidatum, a species with no apparentadaptations to drought, drought stress in combination with light resulted inan increase of tocopherols from 35 nmol mol–1 chl(treatment I) to 400 nmol (treatment IV). This effect was not significant inthe drought-deciduous species with succulent rhizomes,Po. puberulum (about 10 nmolmol–1 chl) and Ph. areolatum(5 to maximum 40 nmol), which experience little desiccation under fieldconditions. This short-term induction of tocopherols and carotenoids has notbeen reported for other plants under light stress and is probably related tothe epiphytic life form.

Identification of the elusive carotenoid isomerase enzyme redefines carotenoid biosynthesis and reveals a role for carotenoids in the membrane dynamics of plastid development

Carotenoids are essential photoprotective and antioxidant pigments synthesized by all photosynthetic organisms. Most carotenoid biosynthetic enzymes were thought to have evolved independently in bacteria and plants. In bacteria, a single enzyme catalyzes four desaturations leading from colorless phytoene to red lycopene, while in plants two desaturases, unrelated to the bacterial enzyme, are required. We have demonstrated that carotenoid desaturation in plants requires a third and different enzyme, the carotenoid isomerase (CrtS). Mutations disrupting CrtS in Arabidopsis cause accumulation of poly-cis carotenoids in the etioplast, the progenitor plastid of dark-grown plants and reveal a requirement for all-trans carotenoids in formation of the prolamellar body (PLB), the lattice of membranes that defines an etioplast. The absence of PLBs in CrtS mutants demonstrates a function for this unique structure in facilitating chloroplast development during the first critical days of seedling germination and photomorphogenesis.

Carotenoids and chronic diseases.

Chronic diseases such as cancer and cardiovascular diseases are the major causes of deaths in North America. Dietary intake of fruits and vegetables has been suggested to have protective effects against such chronic diseases. Carotenoids are important plant pigments which are thought to contribute towards the beneficial effects of fruit and vegetable consumption. This review focuses on the role of carotenoids and particularly lycopene in chronic diseases.

Dietary carotenoids and risk of gastric cancer: a case-control study in Uruguay.

In the period 1997-1999, 120 incident and histologically verified cases of stomach cancer were frequency matched on age, sex, residence and urban/rural status with 360 controls in order to study the role of diet in gastric cancer in Uruguay. Our attention was focused on the role of carotenoids in gastric carcinogenesis, after controlling for major confounders. According to the results, vitamin A, alpha-carotene and lycopene were associated with strong inverse relationships with stomach cancer (OR of stomach cancer for high alpha-carotene intake 0.34, 95% CI 0.17-0.65). Joint exposure to high intakes of alpha-carotene and vitamin C intakes were associated with a strong reduction in risk (OR 0.11, 95% CI 0.03-0.36). It was also suggested that high lycopene intake explained most of the reduction in risk of gastric cancer associated with vegetable intake, whereas no such effect was observed for fruit intake.

Biosynthesis of carotenoids in the chloroplasts of algae and higher plants.

Physiological, biochemical, and genetic aspects of carotenoid biosynthesis in the chloroplast membranes of green algae and higher plants are discussed starting from the earliest stages of biosynthesis of key C5-isoprene units. The latter are synthesized either from acetate (C2) to mevalonic acid (C6) or from glucose (C6) by forming glyceraldehyde 3-phosphate (C3) and pyruvate decarboxylation product (C2) through intermediate compounds to isopentenyl diphosphate (C5). In all organisms, the further carotenoid synthesis from isopentenyl diphosphate and its isomer dimethylallyl diphosphate (C5) proceeds through their transformation into geranyl diphosphate (C10), farnesyl diphosphate (C15), geranylgeranyl diphosphate (C20) and phytoene (C40). Phytoene desaturation (dehydrogenation) to carotene, neurosporene, and lycopene, and all steps of their cyclization to α, β and e carotenes are discussed in detail. The synthesis of xanthophylls in chloroplasts is presented as the sequential formation of hydroxy-, epoxy- and oxo- groups. Genetic control of biosynthesis, as well as the localization and functional role of carotenoids in the chloroplast membranes of plants and algae are briefly discussed.

Diabetes mellitus and serum carotenoids: findings from the Third National Health and Nutrition Examination Survey.

Little is known about carotenoids, a diverse group of plant compounds with antioxidant activity, and their association with diabetes, a condition characterized by oxidative stress. Data from phase I of the Third National Health and Nutrition Examination Survey (1988-1991) were used to examine concentrations of alpha-carotene, beta-carotene, cryptoxanthin, lutein/zeaxanthin, and lycopene in 40- to 74-year-old persons with a normal glucose tolerance (n = 1,010), impaired glucose tolerance (n = 277), newly diagnosed diabetes (n = 148), and previously diagnosed diabetes (n = 230) based on World Health Organization criteria. After adjustment for age, sex, race, education, serum cotinine, serum cholesterol, body mass index, physical activity, alcohol consumption, vitamin use, and carotene and energy intake, geometric means of beta-carotene were 0.363, 0.316, and 0.290 micromol/liter for persons with a normal glucose tolerance, impaired glucose tolerance, and newly diagnosed diabetes, respectively (p = 0.004 for linear trend), and geometric means for serum lycopene were 0.277, 0.259, and 0.231 micromol/liter, respectively (p = 0.044 for linear trend). All serum carotenoids were inversely related to fasting serum insulin after adjustment for confounders (p < 0.05 for each carotenoid). If confirmed, these data suggest new opportunities for research that include exploring a possible role for carotenoids in the pathogenesis of insulin resistance and diabetes.

The role of carotenoids in modulating DNA stability and lipid peroxidation. Importance for human health.

Carotenoids are red, yellow, and orange pigments that absorb light in the 400- to 500-nm region of the visible spectrum (Isler, 1971). They are synthesized by photosynthetic microorganisms and plants, but not by animals. Particularly rich sources are yellow-orange fruits and dark green, leafy vegetables. About 700 naturally occurring carotenoids have been identified, of which about 50 can serve as precursors for vitamin A (Olsen, 1992). All are primarily symmetrical, C-40, polyisoprenoid structures with an extensive conjugated double-bond system (Fig. 1). The conjugated backbone of isoprene units is usually inverted at the center of the molecule, imparting the symmetry. Changes in the geometrical configuration about the double bonds result in many cis and trans isomers.

The role of carotenoids in the structural and functional stability of thylakoids in plastids of dark-grown spruce seedlings

Summary The ability of cotyledons of spruce seedlings to develop their photosynthetic apparatus when grown in the dark was used to study the effect of the «bleaching» herbicide norflurazon (NF) on the formation of their etiochloroplasts. Ultrastructural analyses showed that in etiochloroplasts of cotyledons of 14-day-old seedlings grown in the dark on NF, the number of thylakoids, in particular of grana-thylakoids, was reduced. In plastids resulting after growth on a 200 μmol/L solution of NF, only single thylakoids developed, while in those developed after growth on 20 μmol/L of NF, incomplete stacking of thylakoids appeared. Lower concentrations of NF were less harmful, so that etiochloroplasts with grana regions developed. NF did not influence the formation of prolamellar bodies in the etiochloroplasts. Very strong reduction of carotenoid content, in particular of carotenes and violaxanthin, was obtained after growth of the seedlings in the dark on 200 and 20 μmol/L of NF. At the same time, the content of chlorophylls was also reduced, although to a much lesser degree than that of carotenoids. Analyses of membrane proteins indicated that in these etiochloroplasts the content of polypeptides of LHC II, the major light-harvesting complexes of PS II, was impaired. Only seedlings with less altered plastids were able to develop some photosynthetic activity. High concentrations of NF (200 and 20 μmol/L) caused bleaching of the cotyledons and damage of their plastids when seedlings germinated in the dark were transferred to the light and illuminated for several days.

Dietary retinoids and carotenoids in rodent models of mammary tumorigenesis.

In this review of the scientific literature the relationship between retinoids, carotenoids, and mammary carcinogenesis is examined. Several retinoids have shown promise as chemopreventive agents against chemically induced mammary carcinogenesis in mice and especially in rats. The most promising retinoids are retinyl acetate (RA) and N-(4-hydroxyphenyl)retinamide (4-HPR, fenretinide). In rats, dietary administration of these retinoids reduced tumor incidence and multiplicity, and increased the latency of DMBA or MNU-induced mammary cancers. In mice, 4-HPR reduced the number of hyperplastic alveolar nodules and the number of tumors in MTV- and MTV+ mice, respectively. Among retinoids, 4-HPR is at present the most promising analogue, due to its ability to concentrate in the mammary gland. The combination of 4-HPR with tamoxifen not only is more effective in suppressing breast cancer than either agent alone, but also inhibits the appearance of subsequent cancers following the surgical removal of the first tumor. These studies suggest that retinoids, like tamoxifen, may be applicable to the prevention of contralateral breast cancer in women who underwent breast cancer surgery. It is also becoming evident that differentiation therapy and chemoprevention can become attractive alternative approaches to intensive cytotoxic chemotherapy. The role of carotenoids in the prevention of mammary carcinogenesis, however, is ambiguous. Poor absorption and low levels of carotenoids that reach the target tissues complicate interpretation of data in rodent models of mammary carcinogenesis. Very few animal studies are presently available in which purified carotenoids were found effective against mammary carcinogenesis. These results do not justify undertaking clinical evaluation of individual carotenoids against breast cancer at this time.

Electronic Interactions in Photosynthetic Light-Harvesting Complexes: The Role of Carotenoids

The origin and distance dependence of the electronic interactions which promote energy transfer within photosynthetic light-harvesting complexes is investigated. A model based on localized molecular orbitals is related to canonical molecular orbital calculations, therefore demonstrating its practical utility and allowing us to interpret the results of CAS-SCF calculations of the coupling between donor−acceptor pairs. We then focus on the mechanism of energy transfer involving the carotenoid 21Ag (S1) electronic state: [carotenoid (21Ag) (Car) to carotenoid (21Ag)] and [carotenoid (21Ag) to bacteriochlorophyll (Qy) (Bchl)] interactions. The Car−Car coupling is found to involve reasonably long-range interaction terms, with a primary contribution from dispersion-type interactions, which have an R6 distance dependence. The primary contributor to the Car-Bchl S1 → S1 energy transfer mechanism is suggested to be proportional to the product of dipole−dipole and polarization interactions. In neither case does th...

Carotenoids and retinoids: a review of research, clinical, and public health applications.

Traditionally, the carotenoids and retinoids have been regarded as dietary sources of vitamin A and have been evaluated regarding their respective physiologic roles in vision, growth, immune system integrity, and prevention of vitamin A deficiency. In the 1990s, however, vitamin A deficiency is no longer widespread in Western countries. Therefore, the role of carotenoids and retinoids is evolving to encompass treatment and prevention of conditions such as cancer and cardiovascular disease, which are prevalent in Western societies. This review summarizes current research concerning the therapeutic utility of vitamin A and its analogues and their roles in the prevention of cancer and cardiovascular disease.

Quenching of chlorophyll fluorescence in the major light-harvesting complex of photosystem II: a systematic study of the effect of carotenoid structure.

The role of carotenoids in quenching of chlorophyll fluorescence in the major light-harvesting complex of photosystem II has been studied with a view to understanding the molecular basis of the control of photoprotective nonradiative energy dissipation by the xanthophyll cycle in vivo. The control of chlorophyll fluorescence quenching in the isolated complex has been investigated in terms of the number of the conjugated double bonds for a series of carotenoids ranging from n = 5-19, giving an estimated first excited singlet state energy from 20,700 cm-1 to 10,120 cm-1. At pH 7.8 the addition of exogenous carotenoids with >=10 conjugated double bonds (including zeaxanthin) stimulated fluorescence quenching relative to the control with no added carotenoid, whereas those with n </= 9 conjugated double bonds (e.g., violaxanthin) had no effect on fluorescence. When quenching in the light-harvesting complex of photosystem II was induced by a lowering of pH to 5.5, carotenoids with n </= 9 conjugated double bonds (including violaxanthin) caused a noticeable inhibition of fluorescence quenching relative to the control. Of the 10 carotenoids tested, quenching induced by the addition of the tertiary amine compound, dibucaine, to isolated light-harvesting complex of photosystem II could only be reversed by violaxanthin. These results are discussed in terms of the two theories developed to explain the role of zeaxanthin and violaxanthin in nonphotochemical quenching of chlorophyll fluorescence.

Carotenoids in mollusca: approaching the functions

Carotenoids in eight species of freshwater and sea mollusks were investigated. In the nonreproductive organs of all species, only all-trans C 40-xanthophylls were found. Carotenes are limited to hepatopancreas. No carotenoid derivatives or carotenoids with < 10 conjugated double bonds were detected. Carotenoids in molluskan cells are present in all subcellular fractions; the major part of them is located in plasma membrane. There are no special carotenoid-containing pigmented granules (“cytosomes” “carotenoxysomes”) in molluskan cells. Comparison of both Raman and absorption spectra of carotenoids in situ with those in CHCI 3 suggests that pigments are dissolved in lipid matrix of membranes and not bound to proteins. No changes of carotenoid content or carotenoid pattern in Dreissena polymorpha, Unio pictorum and Viviparus contectus were observed during 10 days of starvation. There were no changes in isolated gills within 2 days as well. In the freshwater species with the exception of D. polymorpha, carotenoid content changes after the fast water temperature changes: with elevation of temperature, the carotenoid content in organs increases and vice versa, without any change in carotenoid composition. This phenomenon is shown to be due to rearrangement of pigments between the hepatopancreas and other organs. The results suggest that the role of carotenoids in molluskan tissues is not connected with their chemical transformations. The most probable function of carotenoids in mollusks is the stabilisation of cell membranes' fluidity.

Structure and properties of carotenoids in relation to function.

The basic principles of structure, stereochemistry, and nomenclature of carotenoids are described and the relationships between structure and the chemical and physical properties on which all the varied biological functions and actions of carotenoids depend are discussed. The conjugated polyene chromophore determines not only the light absorption properties, and hence color, but also the photochemical properties of the molecule and consequent light-harvesting and photoprotective action. The polyene chain is also the feature mainly responsible for the chemical reactivity of carotenoids toward oxidizing agents and free radicals, and hence for any antioxidant role. In vivo, carotenoids are found in precise locations and orientations in subcellular structures, and their chemical and physical properties are strongly influenced by other molecules in their vicinity, especially proteins and membrane lipids. In turn, the carotenoids influence the properties of these subcellular structures. Structural features such as size, shape, and polarity are essential determinants of the ability of a carotenoid to fit correctly into its molecular environment to allow it to function. A role for carotenoids in modifying structure, properties, and stability of cell membranes, and thus affecting molecular processes associated with these membranes, may be an important aspect of their possible beneficial effects on human health.--Britton, G. Structure and properties of carotenoids in relation to function.

Diurnal rhythm of beta-carotene in photosynthetic alga Gonyaulax polyedra.

Carotenoids comprise one of the most widespread classes of pigments found in nature. Polyene pigments from the dinoflagellate Gonyaulax polyedra were extracted every hour over a 24 hour period and the levels of beta-carotene during the day-phase were found to be twice as high as during the night-phase period. Using the thermal decomposition of 1,4-dimethylnaphthalene endoperoxide, the overall quenching ability of beta-carotene and G. polyedra carotenoids of singlet oxygen were found to be 2.04 x 10(9) M-1 s-1 and 4.75 x 10(9) M-1 s-1 respectively. Such a high quenching rate constant suggest a possible role for carotenoids as effective singlet oxygen quenchers in G. polyedra. The dose response curve for light-induced carotenoid synthesis shows a linear response up to 45 minutes of light exposure, after which night phase cells contain the same levels of beta-carotene as day-phase cells. Cells exposed to light pulses at different times during the night period display the highest beta-carotene induction in the middle of the night.

Developments in world aquaculture, feed formulations and role of carotenoids

Abstract

Role of Carotenoids in the Immune Response

The well-established provitamin A activities of certain carotenoids have hampered past research into their possible specific functions. More recently, research interests on carotenoids have been revived, largely because of their anticancer activities. β-Carotene and other carotenoids have been reported to possess immunomodulatory activities in humans and animals. These carotenoids enhance lymphocyte blastogenesis, increase the population of specific lymphocyte subsets, increase lymphocyte cytotoxic activity, and stimulate the production of various cytokines. In addition, carotenoids also stimulate the phagocytic and bacteria-killing ability of blood neutrophils and peritoneal macrophages. The action of these carotenoids is widely accepted to be independent of their provitamin A activity. The immunostimulatory action of carotenoids may be translated into improved health, including mammary and reproductive health in dairy cattle. More studies are needed to establish fully the beneficial effects of supplementation of different carotenoids on the health of dairy cattle. Furthermore, studies on carotenoids other than β-carotene are needed.

Serum levels of β-carotene and other carotenoids in Parkinson's disease

To elucidate the possible role of carotenoids in the risk for developing Parkinson's disease (PD), we compared serum levels of β-carotene, α-carotene and lycopene, measured by high performance liquid chromatography, of 61 PD patients using their spouses as the control group. The serum levels of these 3 carotenoids did not differ significantly between PD patients and control groups. There was no influence of antiparkinsonian therapy on serum carotenoids levels, and these did not correlate with age, age at onset, scores of the Unified Parkinson Disease Rating Scale or the Hoehn and Yahr staging in the PD group. These results show that serum carotenoids concentrations are apparently unrelated to the risk for developing PD.

Antioxidant role of carotenoids in Phaffia rhodozyma

Summary: The role of carotenoids in protecting the yeast Phaffia rhodozyma against reactive oxygen species was studied. Addition of the O2 −-generator duroquinone (DQ) to yeast-malt broth increased total carotenoid content as well as the relative amounts of xanthophylls present, while the reactive oxygen scavenger mannitol reversed this effect. Resistance to DQ increased in the stationary phase, particularly in the carotenoid-hyperproducing strain studied. Assay of superoxide dismutase (SOD) in P. rhodozyma indicated the presence of Mn-SOD and the complete absence of Fe-SOD and Cu/Zn-SOD. Catalase activity in P. rhodozyma was significantly lower than in Saccharomyces cerevisiae, particularly in stationary cultures. In young cells, H2O2 resistance was directly related to carotenoid levels, and selection of cultures based on peroxide resistance resulted in slightly increased carotenoid production. These results indicate that carotenoids play an antioxidant role during ageing in P. rhodozyma.