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Carotenoids perform multifaceted roles in life ranging from coloration over light harvesting to photoprotection. The Orange Carotenoid Protein (OCP), a light-driven photoswitch involved in cyanobacterial photoprotection, accommodates a ketocarotenoid vital for its function. OCP extracts its ketocarotenoid directly from membranes, or accepts it from homologs of its C-terminal domain (CTDH). The CTDH from Anabaena (AnaCTDH) was shown to be important for carotenoid transfer and delivery from/to membranes. The C-terminal tail of AnaCTDH is a critical structural element likely serving as a gatekeeper and facilitator of carotenoid uptake from membranes. We investigated the impact of amino acid substitutions within the AnaCTDH-CTT on echinenone and canthaxanthin uptake from DOPC and DMPG liposomes. The transfer rate was uniformly reduced for substitutions of Arg-137 and Arg-138 to Gln or Ala, and depended on the lipid type, indicating a weaker interaction particularly with the lipid head group. Our results further suggest that Glu-132 has a membrane-anchoring effect on the PC lipids, specifically at the choline motif as inferred from the strongly different effects of the CTT variants on the extraction from the two liposome types. The substitution of Pro-130 by Gly suggests that the CTT is perpendicular to both the membrane and the main AnaCTDH protein during carotenoid extraction. Finally, the simultaneous mutation of Leu-133, Leu-134 and Leu-136 for alanines showed that the hydrophobicity of the CTT is crucial for carotenoid uptake. Since some substitutions accelerated carotenoid transfer into AnaCTDH while others slowed it down, carotenoprotein properties can be engineered toward the requirements of applications., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Carotenoids are pigments of diverse functions ranging from coloration over light-harvesting to photoprotection. Yet, the number of carotenoid-binding proteins, which mobilize these pigments in physiological media, is limited, and the mechanisms of carotenoid mobilization are still not well understood. The same applies for the determinants of carotenoid uptake from membranes into carotenoproteins, especially regarding the dependence on the chemical properties of membrane lipids. Here, we investigate xanthophyll uptake capacity and kinetics of a paradigmatic carotenoid-binding protein, the homolog of the Orange Carotenoid Protein's C-terminal domain from Anabaena sp. PCC 7120 (AnaCTDH), using liposomes formed from defined lipid species and loaded with canthaxanthin (CAN) and echinenone (ECN), respectively. Phospholipids with different chain length and degree of saturation were investigated. The composition of carotenoid-loaded liposomes directly affected the incorporation yield and storage ratio of CAN and ECN as well as the rate of carotenoid uptake by AnaCTDH. Generally, saturated PC lipids were identified as unsuitable, and a high phase transition temperature of the lipids negatively affected the carotenoid incorporation and storage yield. For efficient carotenoid transfer, the velocity increases with increasing chain length or membrane thickness. An average transfer yield of 93 % and 43 % were obtained for the formation of AnaCTDH(CAN) and AnaCTDH(ECN) holoproteins, respectively. In summary, the most suitable lipids for the formation of AnaCTDH(CAN/ECN) holoproteins by carotenoid transfer from artificial liposomes are phosphatidylcholine (18:1) and phosphatidylglycerol (14:0). Thus, these two lipids provide the best conditions for further investigation of lipid-protein interaction and the carotenoid uptake process., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Valorization, the process whereby waste materials are converted into more valuable products, is rarely practiced in industrial fermentation. We developed a model valorization system whereby Saccharomyces cerevisiae that had previously been engineered to produce high concentrations (>100 g/L) of extracellular β-farnesene was further engineered to simultaneously produce intracellular carotenoids, both products being isoprenoids. Thus, a single fermentation generates two valuable products, namely, β-farnesene in the liquid phase and carotenoids in the solid biomass phase. Initial attempts to produce high levels of canthaxanthin (a ketocarotenoid used extensively in animal feed) in a β-farnesene production strain negatively impacted both biomass growth and β-farnesene production. A refined approach used a promoter titration strategy to reduce β-carotene production to a level that had minimal impact on growth and β-farnesene production in fed-batch fermentations and then engineered the resulting strain to produce canthaxanthin. Further optimization of canthaxanthin coproduction used a bioprospecting approach to identify ketolase enzymes that maximized conversion of β-carotene to canthaxanthin. Finally, we demonstrated that β-carotene is not present in the extracellular β-farnesene at a significant concentration and that which is present can be removed by a simple distillation, indicating that β-farnesene (the primary fermentation product) purity is unaffected by coproduction of carotenoids.

Orange carotenoid protein (OCP) of photosynthetic cyanobacteria binds to ketocarotenoids noncovalently and absorbs excess light to protect the host organism from light-induced oxidative damage. Herein, we found that mutating valine 40 in the α3 helix of Gloeocapsa sp. PCC 7513 (G l OCP1) resulted in blue- or red-shifts of 6-20 nm in the absorption maxima of the lit forms. We analyzed the origins of absorption maxima shifts by integrating X-ray crystallography, homology modeling, molecular dynamics simulations, and hybrid quantum mechanics/molecular mechanics calculations. Our analysis suggested that the single residue mutations alter the polar environment surrounding the bound canthaxanthin, thereby modulating the degree of charge transfer in the photoexcited state of the chromophore. Our integrated investigations reveal the mechanism of color adaptation specific to OCPs and suggest a design principle for color-specific photoswitches.

Singlet exciton fission is the spin-allowed generation of two triplet electronic excited states from a singlet state. Intramolecular singlet fission has been suggested to occur on individual carotenoid molecules within protein complexes provided that the conjugated backbone is twisted out of plane. However, this hypothesis has been forwarded only in protein complexes containing multiple carotenoids and bacteriochlorophylls in close contact. To test the hypothesis on twisted carotenoids in a "minimal" one-carotenoid system, we study the orange carotenoid protein (OCP). OCP exists in two forms: in its orange form (OCPo), the single bound carotenoid is twisted, whereas in its red form (OCPr), the carotenoid is planar. To enable room-temperature spectroscopy on canthaxanthin-binding OCPo and OCPr without laser-induced photoconversion, we trap them in a trehalose glass. Using transient absorption spectroscopy, we show that there is no evidence of long-lived triplet generation through intramolecular singlet fission despite the canthaxanthin twist in OCPo.

Our analysis of the X-ray crystal structure of canthaxanthin (CAN) showed that its ketolated β-ionone rings can adopt two energetically equal, but structurally distinct puckers. Quantum chemistry calculations revealed that the potential energy surface of the β-ionone ring rotation over the plane of the conjugated π-system in carotenoids depends on the pucker state of the β-ring. Considering different pucker states and β-ionone ring rotation, we found six separate local minima on the potential energy surface defining the geometry of the keto-β-ionone ring-two cis and one trans orientation for each of two pucker states. We observed a small difference in energy and no difference in relative orientation for the cis-minima, but a pronounced difference for the position of trans-minimum in alternative pucker configurations. An energetic advantage of β-ionone ring rotation from a specific pucker type can reach up to 8 kJ/mol ([Formula: see text]). In addition, we performed the simulation of linear absorption of CAN in hexane and in a unit cell of the CAN crystal. The electronic energies of [Formula: see text] transition were estimated both for the CAN monomer and in the CAN crystal. The difference between them reached [Formula: see text], which roughly corresponds to the energy gap between A and B pucker states predicted by theoretical estimations. Finally, we have discussed the importance of such effects for biological systems whose local environment determines conformational mobility, and optical/functional characteristics of carotenoid., (© 2022. The Author(s), under exclusive licence to Springer Nature B.V.)

A novel strain of Coelastrella terrestris (Chlorophyta) was collected from red mucilage in a glacier foreland in Iceland. Its morphology showed characteristic single, ellipsoidal cells with apical wart-like wall thickenings. Physiological characterization revealed the presence of the rare keto-carotenoid adonixanthin, as well as high levels of unsaturated fatty acids of up to 85%. Initial screening experiments with different carbon sources for accelerated mixotrophic biomass growth were done. Consequently, a scale up to 1.25 L stirred photobioreactor cultivations yielded a maximum of 1.96 mg·L -1 adonixanthin in free and esterified forms. It could be shown that supplementing acetate to the medium increased the volumetric productivity after entering the nitrogen limitation phase compared to autotrophic control cultures. This study describes a promising way of biotechnological adonixanthin production using Coelastrella terrestris .

In this trial, the interaction between two different light resource and different levels of two pigments was investigated in order to determine their effects on growth and reproductive performance of the ornamental fish swordtail ( Xiphophorus helleri ) broodstock. Fish were fed with different levels of 50, 100 and 200 mg · kg-1 of astaxanthin or canthaxanthin, under two different light conditions (natural and artificial). The obtained results were more evident in animals fed with astaxanthin in comparison to canthaxanthin. Furthermore, swordtails reared under artificial light in comparison to the natural light source showed better performance. Overall the greatest effect was for the fish treated with medium dose of astaxanthin (100 mg.kg-1), under the artificial light conditions of rearing. Results indicated the important effects of all three factors (light source, dosage and carotenoids type), with significant interactions between the carotenoid dosage with carotenoid type and light source.

Carotenoids, one of the most common types of natural pigments, can influence the colors of living organisms. More than 750 kinds of carotenoids have been identified. Generally, carotenoids occur in organisms at low levels. However, the total amount of carotenoids in nature has been estimated to be more than 100 million tons. There are two major types of carotenoids: carotene (solely hydrocarbons that contain no oxygen) and xanthophyll (contains oxygen). Carotenoids are lipid-soluble pigments with conjugated double bonds that exhibit robust antioxidant activity. Many carotenoids, particularly astaxanthin (ASX), are known to improve the antioxidative state and immune system, resulting in providing disease resistance, growth performance, survival, and improved egg quality in farmed fish without exhibiting any cytotoxicity or side effects. ASX cooperatively and synergistically interacts with other antioxidants such as α-tocopherol, ascorbic acid, and glutathione located in the lipophilic hydrophobic compartments of fish tissue. Moreover, ASX can modulate gene expression accompanying alterations in signal transduction by regulating reactive oxygen species (ROS) production. Hence, carotenoids could be used as chemotherapeutic supplements for farmed fish. Carotenoids are regarded as ecologically friendly functional feed additives in the aquaculture industry.

Recently a new family of carotenoproteins, homologues of the N-terminal domain of the orange carotenoid protein (NTD-OCP), have been identified in cyanobacteria. These homologues are called helical carotenoid proteins (HCPs) as they are all predicted to maintain the all-helical structure of the NTD-OCP and to bind carotenoids. Here, HCP2 and HCP3 isolated from the cyanobacterium Tolypothrix PCC 7601 were studied by ultrafast transient absorption spectroscopy to explore the excited-state dynamics of the bound carotenoid, canthaxanthin. The lowest excited state, S 1 , of canthaxanthin in both HCPs yields a lifetime of 3.5 ps; it is thus shorter than for canthaxanthin in solution (4.5 ps). This is because of the longer effective conjugation of canthaxanthin in HCPs, as one of the terminal rings is in an s-trans configuration. Use of two different excitation wavelengths, 470 and 570 nm, revealed excitation wavelength dependent spectroscopic response. Additional excited-state absorption bands are observed after excitation at 470 nm for both HCPs, proving the presence of more than one ground state conformer.

This article reviews the excited-state quenching, pro-vitamin A activity and anticarcinogenicity of carotenes and xanthophylls in relation to their chemical structures. Excited-state quenching improved with the length of the conjugated chain structure. Pro-vitamin A activity was dependent on the presence of at least one beta-ionyl ring structure. The effectiveness of carotenoids as antioxidants depended on their ability to trap peroxyl radicals with production of resonance-stabilized carotenyl radicals. The products identified from oxidations of carotenes and xanthophylls with molecular oxygen and other oxidizing agents are presented. The free radical-mediated mechanisms that have been proposed to account for the different classes of products are reviewed.

Carotenoid composition has been studied in mesophilic, nitrogen-fixing cyanobacterium Anabaena sp. PCC7120 grown photoautotrophically, under diazotrophic conditions at four different temperatures (15 °C, 23 °C, 30 °C and 37 °C). The relative accumulation of chlorophyll, carotenoids and proteins was the highest at temperature of 23 °C. At a suboptimal temperature (15 °C) β-carotene was the dominant carotenoid compound, whereas the increase in temperature caused ketocarotenoids (echinenone, canthaxanthin, keto-myxoxanthophyll) to accumulate. A significant increase in the accumulation of phytoene synthase (CrtB) transcript was observed at both extreme growth temperatures (15 °C and 37 °C). The relative amount of β-carotene ketolase (CrtW) transcript directly corresponded to the accumulation of its product (keto-myxoxanthophyll) with a maximum at 30 °C and a profound decrease at 37 °C, whereas the transcription level of β-carotene ketolase (CrtO) was significantly decreased only at a suboptimal temperature (15 °C). These results show that temperature affects the functioning of the carotenoid biosynthesis pathway in Anabaena cells under photoautotrophic growth. Specifically, the balance between β-carotene and ketocarotenoids is altered according to temperature conditions. The transcriptional regulation of genes encoding enzymes active both at the early (CrtB) and the final steps (CrtO, CrtW) of the carotenoid biosynthetic pathway may participate in the acclimation mechanism of cyanobacteria to low and high temperatures., (Copyright © 2019 Elsevier GmbH. All rights reserved.)

The utilization of microalgae as a source of carotenoid productions has gained increasing popularity due to its advantages, such as a relatively fast turnaround time. In this study, a newly discovered Coelastrum sp. TISTR 9501RE was characterized and investigated for its taxonomical identity and carotenoid profile. To the best of our knowledge, this report was the first to fully investigate the carotenoid profiles in a microalga of the genus Coelastrum . Upon use of limited nutrients as a stress condition, the strain was able to produce astaxanthin, canthaxanthin, and lutein, as the major carotenoid components. Additionally, the carotenoid esters were found to be all astaxanthin derivatives, and β-carotene was not significantly present under this stress condition. Importantly, we also demonstrated that this practical stress condition could be combined with simple growing factors, such as ambient sunlight and temperature, to achieve even more focused carotenoid profiles, i.e., increased overall amounts of the aforementioned carotenoids with fewer minor components and chlorophylls. In addition, this green microalga was capable of tolerating a wide range of salinity. Therefore, this study paved the way for more investigations and developments on this fascinating strain, which will be reported in due course.

The remarkable drought-resistance of the terrestrial cyanobacterium Nostoc flagelliforme (N. flagelliforme) has attracted attention for many years. In this study, we purified a group of red proteins that accumulate in dried field samples of N. flagelliforme. These red proteins contain canthaxanthin as the bound chromophore. Native-PAGE analysis revealed that the purified red proteins resolved into six visible red bands and were composed of four helical carotenoid proteins (HCPs), HCP1, HCP2, HCP3, and HCP6 (homologs to the N-terminal domain of the orange carotenoid protein (OCP)). Seven genes encode homologs of the OCP in the genome of N. flagelliforme: two full-length ocp genes (ocpx1 and ocpx2), four N-terminal domain hcp genes (hcp1, hcp2, hcp3, and hcp6), and one C-terminal domain ccp gene. The expression levels of hcp1, hcp2, and hcp6 were highly dependent on the water status of field N. flagelliforme samples, being downregulated during rehydration and upregulated during subsequent dehydration. Transcripts of ocpx2 were dominant in the dried field samples, which we confirmed by detecting the presence of OCPx2-derived peptides in the purified red proteins. The results shed light on the relationship between carotenoid-binding proteins and the desiccation resistance of terrestrial cyanobacteria, and the physiological functions of carotenoid-binding protein complexes in relation to desiccation are discussed.

For nine symmetric natural carotenoids, a comprehensive thermodynamics study of processes associated with their radical scavenging activity is proposed. We have investigated the hydrogen atom transfer (HAT) from the parent carotenoid, mono-radical species, radical cations and radical anions. Electron transfer and proton transfer reactions were also studied. Terminal units and carbon atoms in their vicinity were identified as thermodynamically favoured reaction sites of the HAT mechanism. Rhodoxanthin, canthaxanthin and astaxanthin, as strong antioxidants, without any pro-oxidative effect, were found to have bond dissociation enthalpies (BDE) higher than 300 kJ mol -1 and the most negative electron affinities. The electron transfer to a carotenoid is exothermic, while other studied reactions are endothermic. In solvent, the electron transfer reactions may be preferred instead of hydrogen atom transfer., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Carotenoids are valuable natural colorants that exhibit numerous health promoting properties, and thus are widely used in food, feeds, pharmaceutical and nutraceuticals industries. In this study, we isolated and identified novel microbial sources that produced high-value carotenoids using high throughput screening (HTS). A total of 701 pigmented microbial strains library including marine bacteria and red yeast was constructed. Carotenoids profiling using HPLC-DAD-MS methods showed 88 marine bacterial strains with potential for the production of high-value carotenoids including astaxanthin (28 strains), zeaxanthin (21 strains), lutein (1 strains) and canthaxanthin (2 strains). A comprehensive 16S rRNA gene based phylogenetic analysis revealed that these strains can be classified into 30 species belonging to five bacterial classes (Flavobacteriia, α-Proteobacteria, γ-Proteobacteria, Actinobacteria and Bacilli). Importantly, we discovered novel producers of zeaxanthin and lutein, and a high diversity in both carotenoids and producing microbial strains, which are promising and highly selective biotechnological sources for high-value carotenoids., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Light-driven H + , Cl - and Na + rhodopsin pumps all use a covalently bound retinal molecule to capture light energy. Some H + -pumping rhodopsins (xanthorhodopsins; XRs) additionally contain a carotenoid antenna for light absorption. Comparison of the available primary and tertiary structures of rhodopsins pinpointed a single Thr residue (Thr216) that presumably prevents carotenoid binding to Na + -pumping rhodopsins (NaRs). We replaced this residue in Dokdonia sp. PRO95 NaR with Gly, which is found in the corresponding position in XRs, and produced a variant rhodopsin in a ketocarotenoid-synthesising Escherichia coli strain. Unlike wild-type NaR, the isolated variant protein contained the tightly bound carotenoids canthaxanthin and echinenone. These carotenoids were visible in the absorption, circular dichroism and fluorescence excitation spectra of the Thr216Gly-substituted NaR, which indicates their function as a light-harvesting antenna. The amino acid substitution and the bound carotenoids did not affect the NaR photocycle. Our findings suggest that the antenna function was recently lost during NaR evolution but can be easily restored by site-directed mutagenesis.

Carotenoids relevance as natural pigments is mainly due to their uses as colorants, feed supplements, nutraceuticals and for medical, cosmetic, and biotechnological purposes. Since they have putative health beneficial effects, the demand and market of carotenoids are growing significantly. There is a diversity of natural and synthetic carotenoids, but only a few of them are commercially produced, including carotenes (β-carotene and lycopene) and xanthophylls (astaxanthin, canthaxanthin, lutein, zeaxanthin, and capsanthin). Some biotechnological processes for carotenoids production were established some years ago, but new strains and technologies are being developed nowadays for carotenoids widely in demand. This chapter shows a revision of the main carotenoids from a commercial point of view.

Rhodopseudomonas palustris is a purple photosynthetic bacterium that accumulates in the inner membrane the photosynthetic pigment spirilloxanthin, formed from lycopene. Here, we describe the procedures used to successfully engineer Rps. palustris strains to reroute the production of lycopene toward the synthesis of ß-carotene or canthaxanthin. The crtCD genes specifically involved in spirilloxanthin were replaced by crtY and crtW genes from Bradyrhizobium ORS278 to synthesize ß-carotene and (or) canthaxanthin, two pigments of industrial interest. Since the synthesis of canthaxanthin depends on the presence of oxygen, the procedure to optimize their production is also proposed. By modulating the light and oxygen during the growth process, a single species of photosynthetic bacteria, with an efficient growth rate, produces various carotenoids of economical interest.

Xanthophyllomyces dendrorhous, a heterobasidiomycetous yeast that represents the teleomorphic state of Phaffia rhodozyma, is used as a natural source of several carotenoids, such as the xanthophyll astaxanthin. Here, we describe the culture procedure for the production of carotenoids in X. dendrorhous and a simple and rapid analytical method for the optimized extraction and HPLC determination of intracellular β-carotene, astaxanthin, canthaxanthin, and zeaxanthin.

The aim of the study was to identify and quantitatively assess of carotenoids and isoprenoid quinones biosynthesized by six different strains of acetic acid bacteria, belonging to genus Asaia , that are common beverage-spoiling bacteria in Europe. Bacterial cultures were conducted in a laboratory liquid culture minimal medium with 2% sucrose. Carotenoids and isoprenoid quinones were investigated using UHPLC-DAD-ESI-MS analysis. In general, tested strains of Asaia spp. were able to produce 10 carotenoids and 3 isoprenoid quinones: menaquinone-7, menaquinone-8, and ubiquinone-10. The main identified carotenoids in Asaia lannensis strains were phytofluene, neurosporene, α-carotene, while for Asaia bogorensis , neurosporene, canthaxanthin, and zeaxanthin were noted. What is more, tested Asaia spp. were able to produce myxoxanthophyll, which has so far been identified primarily in cyanobacteria. The results show that A. lannensis are characterized by statistically higher concentrations of produced carotenoids, as well as a greater variety of these compounds. We have noted that carotenoids were not only accumulated by bacterial cells, but also some strains of A. lannensis produced extracellular carotenoids., Competing Interests: The authors declare no conflict of interest.

Astaxanthin, β-cryptoxanthin, canthaxanthin, lutein and zeaxanthin, the major xanthophylls, are widely used in food, medicine, and health care products. To date, no studies regarding the inhibitory effects of these xanthophylls on the nine CYPs isozymes have been reported. This study investigated the reversible and time-dependent inhibitory potentials of five xanthophylls on CYPs activities in vitro. The reversible inhibition results showed that the five compounds had only a weak inhibitory effect on the nine CYPs. Lutein did not inhibit the nine CYPs activities. Astaxanthin weakly inhibited CYP2C19, with an IC₅₀ of 16.2 μM; and β-cryptoxanthin weakly inhibited CYP2C8, with an IC₅₀ of 13.8 μM. In addition, canthaxanthin weakly inhibited CYP2C19 and CYP3A4/5, with IC₅₀ values of 10.9 and 13.9 μM, respectively. Zeaxanthin weakly inhibited CYP3A4/5, with an IC₅₀ of 15.5 μM. However, these IC₅₀ values were markedly greater than the Cmax values reported in humans. No significant IC₅₀ shift was observed in the time-dependent inhibition screening. Based on these observations, it is unlikely that these five xanthophylls from the diet or nutritional supplements alter the pharmacokinetics of drugs metabolized by CYPs. These findings provide some useful information for the safe use of these five xanthophylls in clinical practice., (Copyright © 2013. Published by Elsevier Ltd.)

The pigmentation and corresponding in vivo and in vitro absorption characteristics in three different deep-water coral species: white and orange Lophelia pertusa, Paragorgia arborea and Primnoa resedaeformis, collected from the Trondheimsfjord are described. Pigments were isolated and characterized by High-Performance Liquid Chromatography (HPLC) analysis and High-Performance Liquid Chromatography Time-Of-Flight Mass Spectrometer (LC-TOF MS). The main carotenoids identified for all three coral species were astaxanthin and a canthaxanthin-like carotenoid. Soft tissue and skeleton of orange L. pertusa contained 2 times more astaxanthin g(-1) wet weight compared to white L. pertusa. White and orange L. pertusa were characterized with in vivo absorbance peaks at 409 and 473 nm, respectively. In vivo absorbance maxima for P. arborea and P. resedaeformis was typically at 475 nm. The shapes of the absorbance spectra (400-700 nm) were species-specific, indicated by in vivo, in vitro and the corresponding difference spectra. The results may provide important chemotaxonomic information for pigment when bonded to their proteins in vivo, bio-prospecting, and for in situ identification, mapping and monitoring of corals.

Several studies have correlated the excessive production of prostaglandins (PGs) with tumor promotion and the suppression of the immune response. Inhibition of PGs by pharmacological agents has been demonstrated to enhance immunocompetence, and to suppress growth of tumors in animals and humans. In this study we examined the effect of retinol (I), all-trans-retinoic acid (II), N-(4-Hydroxyphenyl) retinamide (N-4-HPR) (III), canthaxanthin (CTX) (IV), and beta-carotene (beta-CT) (V) on the bioconversion of 14C-arachidonic acid (AA) to PGE2 by squamous carcinoma cells of the tongue, SCC-25. Agents (I), (II), (III), (IV) inhibited while (V) stimulated PGE2 formation in a dose related manner. N-4-HPR was the most potent inhibitor of PGE2 synthesis. The data suggest that certain retinoids and carotenoids have the potential of inhibition of PG synthesis by oral squamous carcinoma cells. Inhibitory effects such as those described here and antioxidant properties might in part contribute to the antiinflammatory and anticarcinogenic activity of retinoids in vivo.

The quantum yield for the photobleaching of astaxanthin (the carotenoid of wild salmonoids) and of canthaxanthin (the closely related carotenoid used as a feeding additive for farmed salmonoids) has been determined for monochromatic light at different wavelengths and in different solvents. Astaxanthin is less sensitive to light than canthaxanthin. The photobleaching is strongly wavelength dependent, and the quantum yield for astaxanthin dissolved in chloroform at 22 degrees C is 3.2 x 10(-1) mol.Einstein-1 at 254 nm, 3.1 x 10(-2) at 313 nm, and 1.6 x 10(-6) at 436 nm, respectively. The quantum yields are less dependent on the nature of the solvent and show no simple correlation with oxygen solubility, i.e. for 366 nm excitation of astaxanthin the quantum yields are 6.1 x 10(-5) mol.Einstein-1 in acetone, 1.2 x 10(-4) in saturated vegetable oil, 1.9 x 10(-4) in chloroform, and 3.4 x 10(-4) solubilized in water, respectively. The photobleaching quantum yield provides an objective measure of the light sensitivity of the carotenoids in relation to the discolouration of carotenoid-pigmented salmonoids. The quantum yield was also found to be independent of the carotenoid concentration and, in a homogenous solution, of light intensities. For astaxanthin solubilized in water, the quantum yield increases for low light intensities. Excitation of astaxanthin solubilized in water using visible light shows that the photobleaching quantum yield is independent of temperature, while excitation at 313 nm shows an increase in the quantum yield with increasing temperatures, corresponding to an energy of activation of 28 kJ.mol-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Using benzo(a)pyrene (BaP) metabolism as a probe for chemical carcinogenesis, in vitro and in vivo effects of palm-oil carotenoid [beta-carotene (BC), alpha-carotene (AC), or canthaxanthin (CTX)] on BaP metabolism in the rat hepatic cytochrome P450-mediated monooxygenase system were studied. Apparent Michaelis-Menten constants (Km) for formation of the precursor carcinogen, 7,8-dihydrodiol BaP, were found to be 14.4 (BC), 1.74 (AC), and 0.7 (CTX) mumol/L. The order of anticarcinogenic strength established in this study was BC much greater than AC greater than CTX. Increased formation of the detoxification intermediate, 3-hydroxy BaP, with increased carotenoid concentration was observed. The order of detoxification strength was BC greater than AC = CTX. The presence of carotenoids in vivo inhibited BaP metabolism. Using 9,10-dihydrodiol BaP as an indicator for inhibition, the order of the antioxidative activity was palm oil (with carotenoids) greater than BC greater than CTX greater than palm oil (without carotenoids). BC and AC may selectively modify the rat-liver microsomal enzymes, thus providing a biochemical mechanism for the inhibitory effect of palm carotenoids on chemical carcinogenesis.

Bladder cancer was induced in male B6D2F1 strain mice by the administration of N-butyl-N-(4-hydroxybutyl)nitrosamine. Mice supplemented with beta-carotene for 5 weeks before receiving the carcinogen and maintained on beta-carotene for an additional 26 weeks developed significantly fewer tumors than did unsupplemented mice. Mice receiving canthaxanthin for the same time period showed no protection against the development of bladder cancer.

Canthaxanthin, a carotenoid with no vitamin A activity, was evaluated for its efficacy in the prevention of chemically induced mammary cancers. Canthaxanthin was administered in the diet at two dose levels (3,390 or 1,130 mg/kg diet). In the dimethylbenzanthracene-induced mammary cancer model, diet supplementation with canthaxanthin for 3 weeks prior to the carcinogen resulted in a 65% reduction in the number of mammary cancers. The feeding of canthaxanthin after the administration of methylnitrosourea had no significant effect on mammary carcinogenesis. These data demonstrate that canthaxanthin, at least in these models of mammary cancer, is active in preventing cancer initiation and not promotion. Analysis of tissues by high-pressure liquid chromatography revealed that canthaxanthin levels in the liver are very high when compared to those in the mammary gland. The observation that canthaxanthin is highly effective in preventing cancer initiation without toxicity suggests that carotenoids not possessing vitamin A activity should be further evaluated as chemopreventive agents.

Serum concentrations of alpha-carotene (AC), beta-carotene (BC), lycopene (LY), beta-cryptoxanthin (CR), zeaxanthin (including lutein. ZX), canthaxanthin (CX), retinol (RE), and alpha-tocopherol (TO) in healthy persons (618 males and 1,196 females) aged 7-86 years were determined by HPLC. Serum concentrations of BC among persons aged 20-49 years were higher with increasing age in females, but not in males. Serum CR concentrations decreased with age ranging from 7 to 39 years, while ZX concentrations rose in the age group of 20 to 59 years for both sexes. In contrast, serum RE concentrations and ratios of RE/BC and RE/CR, especially in males aged 20-49, were higher with age. Serum TO values in both sexes rose with age and were similar.

In a one year-study, 9 healthy human donors were being supplemented with beta-carotene (BC) plus canthaxanthin (CX), to determine the effect of carotenoids on chromosomal damage (micronuclei) induced in the donors' lymphocyte cell cultures by exposure to bleomycin (BLM), an antineoplastic drug that has been shown to produce chromosomal aberrations through the production of free radicals. The first four months monitoring data, including determination of carotenoid blood levels, are here reported. These data show that carotenoid supplementation significantly decrease (up to 50%) the formation of micronuclei induced by BLM in human lymphocyte cell cultures. This decrease is in correlation with carotenoid blood levels.

The absorption and distribution of [14C]-canthaxanthin and [14C]lycopene were studied in rats and in rhesus monkeys following the oral administration of [14C]canthaxanthin or [14C]lycopene in olive oil supplemented with 1 mg alpha-tocopherol/mL. For canthaxanthin and lycopene, peak accumulation of radioactivity in plasma occurred between 4 and 8 h in rats and between 8 and 48 h in monkeys. In rats, the liver contained the largest amount of both kinds of radioactive pigments. In monkeys, with the exception of one stomach sample, liver was also the major depot organ for both canthaxanthin and lycopene. The other organs tested accumulated various amounts of pigment. No labeled metabolic products of either canthaxanthin or lycopene were found.

As reported earlier, crystalline yellow-glistening deposits in the retinal inner layer were identified in 22 of 53 patients treated with PHENORO (containing 10 mg beta-carotene and 15 mg canthaxanthin per capsule) for various light sensitive dermatoses at cumulative doses of canthaxanthin of up to 178 g for up to 12 years. 14 of the 22 patients with deposits could now be investigated again, 5 years after discontinuation of treatment. There was an extensive reduction of the number of deposits, confirming other reports which have demonstrated that the formation of the crystalline deposits is reversible. Analysis of serum samples revealed significant concentrations of canthaxanthin, resulting from the intake of this carotenoid via food.

Aplastic anemia with a fatal outcome occurred in a previously healthy young woman after ingesting canthaxanthin taken for the purpose of skin "tanning" and provided to her by a commercial tanning salon. Canthaxanthin is a synthetic, non-provitamin A carotenoid that is highly lipid-soluble; it colors the skin by deposition in the epidermis and subcutaneous fat. It is readily available through commercial tanning salons and mail advertisements, but despite advertising claims that it is harmless, investigation regarding the safety of oral doses of canthaxanthin in humans has not been conducted. It is not approved as a prescription or an over-the-counter preparation by the Food and Drug Administration. The drug's present means of distribution makes monitoring for toxic effects difficult. Thus, the frequency of adverse effects associated with canthaxanthin use, such as bone marrow suppression, is unknown. Even if there is only a small risk of these toxic effects, the use of the drug for cosmetic purposes does not justify this risk.

The effects of dietary supplementation with retinyl palmitate, canthaxanthin, or the combination of both, on photocarcinogenesis was determined in pigmented C3H/HeN mice. The basal diet was the American Institute of Nutrition Diet 76A, to which was added 120 IU of retinyl palmitate per g diet, 1% canthaxanthin, or the combination of both. Administration of the diets began 18 weeks before the first UVB radiation (280-320 nm) treatment and continued throughout the study. The UV source was a bank of 6 Westinghouse FS40 lamps which delivered to the mice a total dose of 9.9 x 10(5) J/m2, delivered over 24 weeks. These diets significantly reduced the tumor burden per mouse induced by UV irradiation, however they did not influence tumor incidence. The combination of retinyl palmitate plus canthaxanthin was more effective than either agent alone at reducing autochthonous tumor growth, a result which has not been previously reported.

Beta-carotene and canthaxanthin at concentrations of 70 or 300 microM were shown to inhibit the proliferation of cultured human squamous cells (SK-MES lung carcinoma and SCC-25 oral carcinoma) in a 5 hr cell density assay. Responses were similar for both tumor cell lines, ranging from 71-84% inhibition. In contrast, equimolar concentrations of alpha-tocopherol gave only 19-36% inhibition of SCC-25, but 50-75% inhibition of SK-MES cell density. Equimolar reduced glutathione resulted in 4-15% stimulation of SCC-25 and 22-25% inhibition of SK-MES cell proliferation. With cultured normal keratinocytes, treated final cell densities did not differ significantly from those of controls. Two additional assays measuring the metabolic generation of formazan (MTT assay) and [5-3H]thymidine incorporation were in substantial agreement with the growth inhibition pattern. Thus both continuous and cyclic cellular processes are involved in the tumor-specific response. Onset of the response to beta-carotene alone or in combination with alpha-tocopherol is signalled within 1-2 hours of treatment by the appearance of a unique 70 kD heat-shock protein.

Retinoids and certain carotenoids, e.g., beta-carotene and canthaxanthin, have been found to prevent photocarcinogenesis in mice and also to act as immunoenhancers. The hypothesis that retinoids and carotenoids inhibit photocarcinogenesis by preventing UV induction of immunosuppression predicts that mice treated with these agents before and during periods of UV radiation treatments should be as resistant as unirradiated mice to an antigenic UV-induced tumor. To test this prediction, mice were fed 120 IU of retinyl palmitate per gram of diet, and/or 1% canthaxanthin, before UV irradiation treatments began, and during the entire experiment. After 4.95 x 10(5) Jm-2, delivered over 12 weeks, resistance of mice to antigenic UV-induced tumor implants (UV20) was studied. Dietary supplementation with retinyl palmitate plus canthaxanthin, but not with either agent alone at these doses, prevented the enhanced growth of UV20 in UV irradiated mice.

Cancer chemoprevention with beta-carotene (BC), canthaxanthin (CX) and retinol-BC is reported with respect to skin, breast, gastric, colon carcinogeneses induced by benzo(a)pyrene (BP) with or without ultra violet radiation (UV-A, UV-B), dimethylbenzathracene (DMBA) +/- UVB, P-UVA, N-methyl-N'-N-nitro-nitrosoguanidine (MNNG), dimethylhydrazine (DMH), and with respect to transplanted tumours. When animals were loaded with carotenoid supplementation one month before the carcinogenic induction (continued throughout the experiment), cancer prevention was observed up to 60-100%. The absence of provitamin A-activity in CX shows the carotenoid antioxidant property. Fifteen patients given BC + CX to prevent recurrences after radical removal of the primary neoplasia in organs like lung, breast, colon, urinary bladder, head and neck were studied in 1980-89. A longer than expected disease-free interval was preliminarily found. Supplementation of BC +/- retinol was also reported to prevent and treat oral leucoplakia. Supplementation and intermittent retinol administration was also tested in benign cyclical mastalgia with clear cut side effect free therapeutic results.

The carotenoids are a chemically related group of pigments which occur widely and abundantly in nature. Fruits, vegetables and vegetable oils, dairy products, leaves, shrimp, lobster, the plumage of exotic birds, all contain carotenoids. Chemically, the carotenoids may be divided into carotenes, made up of carbon and hydrogen only, and oxycarotenoids containing oxygen in addition to carbon and hydrogen. The use of carotenoid-containing plant extracts for coloring foods has been practiced for centuries and continues today. Advances in chemical synthesis resulted in the complete laboratory synthesis of beta carotene in 1950. Since then the commercial synthesis of several carotenoids has been accomplished. In the U.S. three of these commercially synthesized carotenoids, beta-carotene, beta-apo-8'-carotenal, and canthaxanthin, are accepted color additives for use in foods and are exempt from certification. These three carotenoids are also widely accepted for food use in other countries. This paper deals with the chemistry and synthesis of these three carotenoids, with special emphasis on their numerous commercially available market forms and their characteristics, and on the application of these carotenoids in the coloring of food products.

Long-term treatment with oral carotenoids in 57 patients suffering from a variety of photodermatoses and disorders associated with cutaneous light sensitivity was evaluated. All patients were treated for two or more 6-month periods in separate years. Best therapeutic results were seen in PMLE patients, a good to excellent therapeutic response was noted for 65% of all patients, increasing to 81% of those assigned to skin types III and IV, and decreasing to 47% of those with skin types I and II. The therapeutic effect observed in disorders characterized by other mechanisms than provocation by solar radiation per se was less conspicuous, viz. for light-sensitive psoriasis and lupus erythematosus. Even here, therapeutic failure seems to be more common in individuals with skin types I and II than for skin types III and IV. Photodermatoses such as persistent light reaction, actinic reticuloid and solar urticaria did not respond to any significant degree to carotenoid treatment. Our findings would appear to justify further treatment with oral carotenoids in selected cases of PMLE, and a higher dosage level may be tried for non-responding individuals with light-sensitive psoriasis and DLE or SLE. Serious side effects have not been observed in spite of long-term therapy lasting several years.

Eight "chinchilla bastard" pigmented rabbits were treated intravenously with sonicated phospholipid liposomes (SUV) consisting predominantly of egg yolk phosphatidylcholine (PC). Four rabbits were treated with canthaxanthin incorporated into PC liposomes in a single injection and fractionated over a period of 19 days. The total amount of PC used was a single dose of 260 mg administered as a 50-ml suspension and 13.7 mg/fraction given as a 5-ml suspension. The total amount of canthaxanthin used was a single 40 mg as a 50-ml suspension and 2.1 mg/fraction as 5-ml suspension. Electroretinography showed that canthaxanthin produced a depression of the a-waves and prolongation of the scotopic a- and b-wave peak latencies. A single high-dose injection of PC and PC plus canthaxanthin resulted in a transitory reduction in ERG amplitudes. A single injection of PC and canthaxanthin also produced hypernormal a-waves within the recovery time. Electron microscopy demonstrated that in contrast to the controls (PC), the canthaxanthin-treated rabbits showed alterations in the RPE/photoreceptor complex, indicating that these layers are the primary site of canthaxanthin effects on the retina.

The carotenoids beta-carotene (C) and canthaxanthine (CX), with and without pro-vitamin A activity, respectively, when perorally administered to mice, markedly prevent benzo(a)pyrene photocarcinogenic enhancement (BP-PCE), continue to block such BP-PCE and protect significantly against BP carcinogenesis in mice maintained in the dark. These results appear relevant to both the pathogenesis of chemical carcinogenesis and rational programs of skin cancer prevention in humans.

The significance of carotenoid accumulation in crustacean eggs remains obscure, particularly because neither eggs nor female animals have been found to display specific pigment patterns in relation to reproduction. We report here the first example of carotenoids found exclusively in the ovaries, the eggs, and the hemolymph, but not in the carcass of a female, reproductively active crustacean, i.e. the brine shrimp Artemia. These pigments are virtually absent in males and in immature animals and disappear very rapidly in growing nauplii following hatching of encysted embryos. Within the cysts, they are preferably localized in the yolk platelets. We have identified them as mono-cis- canthaxanthins on the basis of their mass and absorption spectra and by comparison with synthetic components. Carotenoids with the unusual cis-configuration have never been isolated from animals, nor are there reports on the occurrence of carotenoid pigments at specific sites. Our findings may thus provide a clue to a precise function for carotenoids in Artemia and, possibly, related Crustacea.

We performed threshold static perimetry on 19 patients who had ingested canthaxanthin; 11 had maculopathy and eight did not. Patients with no history of canthaxanthin ingestion served as controls. All patients had visual acuity of 6/9 or better. Threshold static perimetry was reevaluated two to three years after cessation of canthaxanthin ingestion. For both testing sessions, patients with maculopathy presented lower retinal sensitivity than controls, while patients without maculopathy did not differ significantly from the control group. These results suggest that canthaxanthin retinopathy can adversely affect the neurosensory retina.

Clinical experiments could demonstrate that beta-carotene and canthaxanthin (Carotinoid-N), orally applied, decreases ultraviolet sensitivity such as manifests itself by erythematous reactions. The dosage administered was 4 dragees daily (1 dragee contains 25 mg beta-carotene and 35 mg canthaxanthin) for two weeks and 2 dragees daily for another two weeks. There was no induction of melanin production observed. In vitiligo, administration of Carotinoid-N failed to induce repigmentation, but the contrast between vitiliginous white patches and the surrounding pigmented skin was markedly reduced by carotinoids deposited in the skin. In addition, sun protection was afforded. Carotinoid-N induced a photoprotecting action in patients with pronounced ultraviolet sensitivity or with polymorphic light eruptions (PLE). In some cases, however, we recommend an additional pretreatment with ultraviolet light ("ultraviolet hyposensitization"). With acne-lesions, the common sun lotions and creams should be avoided: only preparations without emulsifiers may be made use of.