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Special Issue "Carotenoids"

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A special issue of Molecules (ISSN 1420-3049).

Deadline for manuscript submissions: closed (30 November 2011)

Special Issue Editor

Guest Editor
Dr. Hans-Richard Sliwka

Department of Chemistry, Norwegian University of Science and Technology, 7491 Trondheim, Norway

Special Issue Information

Dear Colleagues,

Carotenoids are, by definition, polyenes of 6-14 conjugated double bonds, stabilized by methyl groups and cyclohexene endrings. Straight chain polyenes without these stabilizations only reach 5 double bonds. The major part of the 750 natural carotenoids occurs with 9-11 conjugated double bonds, which may be the effective range regarding stability and activity. Such carotenoids are given as prime examples in textbooks to explain UV-VIS spectroscopy. Carotenoids with a considerably increased number of double bonds have been synthesized to approach λ, the magic absorption limit.

Carotenoids participate in photosynthesis and are, therefore, biosynthesized in plants and alga. Although photosynthesis may appear a long procedure taking place during hours of sunlight exposition the photophysical examination of light absorbing by carotenoids has reached the incredible short span of femtoseconds. In water based environments carotenoids aggregate to micelles and vesicles; increasing effort is directed to study these nano sized structures. Carotenoid chemists have traditionally focused on structure elucidation and on synthesis and various natural occurring carotenoids are also available by synthesis. Eight carotenoids are offered industrially in considerable amounts and are marketed as food and feed colors. Since most carotenoids are hydrophobic, they add to proteins for passing aqueous environments. Hydrophobicity also obstructs an all-purpose assignment of carotenoids and they need extensive formulation before introduced in water-based applications, e.g. as food colors. The pharmacological importance of carotenoids has been limited; a few modified carotenoids for the treatment of cardiovascular and ophthalmological diseases pass now clinical or pharmacokinetic studies. Carotenoids function as molecular wires and modified carotenoids have been developed for electrochemical and spectroscopic research.

Carotenoids are best known as antioxidants. Nevertheless, it is still not clear whether the intact carotenoid is the active agent or one of its oxidative degradation products. A practical impact of carotenoids to the development of chemistry cannot be underestimated: the purification method “chromatography” was invented with these colorful compounds. Carotenoids are the subject of substantial interdisciplinary research. It is hoped that the special issue of Molecules attract researchers who present the various aspects of carotenoid research.

Hans-Richard Sliwka
Guest Editor

Keywords

  • aggregation
  • amphiphiles
  • antioxidants
  • bioorganic chemistry
  • biophysics
  • biosynthesis
  • biotransformations
  • carbocations
  • carotenoids
  • cations
  • chirality
  • chromophores
  • chromatography
  • conjugation
  • cyclic voltammetry
  • density functional calculations
  • electron transfer
  • energy transfer
  • fatty acids
  • fluorescence
  • lipids
  • membranes
  • molecular electronics
  • molecular modeling
  • monolayers
  • nanostructures
  • natural products
  • nonlinear optics
  • photophysics
  • photosynthesis
  • radical ions
  • radicals
  • self-assembly
  • singlet oxygen
  • structure-activity relationships
  • surfactants
  • total synthesis
  • UV/Vis spectroscopy
  • vesicles
  • wittig reactions

Published Papers (16 papers)

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Research

Jump to: Review

Open AccessArticle Influence of Sample Processing on the Analysis of Carotenoids in Maize
Molecules 2012, 17(9), 11255-11268; doi:10.3390/molecules170911255
Received: 4 September 2012 / Revised: 13 September 2012 / Accepted: 13 September 2012 / Published: 21 September 2012
Cited by 10 | PDF Full-text (265 KB) | HTML Full-text | XML Full-text
Abstract
We performed a number of tests with the aim to develop an effective extraction method for the analysis of carotenoid content in maize seed. Mixtures of methanol–ethyl acetate (6:4, v/v) and methanol–tetrahydrofuran (1:1, v/v) were the most effective solvent systems for carotenoid [...] Read more.
We performed a number of tests with the aim to develop an effective extraction method for the analysis of carotenoid content in maize seed. Mixtures of methanol–ethyl acetate (6:4, v/v) and methanol–tetrahydrofuran (1:1, v/v) were the most effective solvent systems for carotenoid extraction from maize endosperm under the conditions assayed. In addition, we also addressed sample preparation prior to the analysis of carotenoids by liquid chromatography (LC). The LC response of extracted carotenoids and standards in several solvents was evaluated and results were related to the degree of solubility of these pigments. Three key factors were found to be important when selecting a suitable injection solvent: compatibility between the mobile phase and injection solvent, carotenoid polarity and content in the matrix. Full article
(This article belongs to the Special Issue Carotenoids)
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Open AccessArticle Stability of Carotenoid Diets During Feed Processing and Under Different Storage Conditions
Molecules 2012, 17(5), 5651-5660; doi:10.3390/molecules17055651
Received: 7 February 2012 / Revised: 4 May 2012 / Accepted: 8 May 2012 / Published: 11 May 2012
PDF Full-text (227 KB)
Abstract
The stability of formulated carotenoid diets during feed processing and under different storage conditions were studied. All carotenoid diets were split into two groups with one group containing BHT (acting as an antioxidant) at 250 ppm and the other without BHT. The [...] Read more.
The stability of formulated carotenoid diets during feed processing and under different storage conditions were studied. All carotenoid diets were split into two groups with one group containing BHT (acting as an antioxidant) at 250 ppm and the other without BHT. The experiment was divided into two parts. First, all diets were evaluated in total carotenoid (TC) loss during feed processing, in dry mixed feeds after being processed and dried. In the final part, the completed dietary carotenoids were stored in an aluminum foil bag, the top of which was sealed with a bag sealer and kept under different storage conditions at 26–28 °C and 4 °C. The stability of the TC was observed during an 8-week trial period. The results showed that the diet pelleting process did not affect the carotenoid content of the diets, and the best storage temperature for the formulated carotenoid diet was at 4 °C. However, an antioxidant was added to assist in energy saving before feed processing. Thus, the addition of BHT at 250 ppm can be done at normal room temperature in order to reduce oxidation that might cause a loss of TC quantities in diets. Full article
(This article belongs to the Special Issue Carotenoids)
Open AccessArticle Diverse Effects of β-Carotene on Secretion and Expression of VEGF in Human Hepatocarcinoma and Prostate Tumor Cells
Molecules 2012, 17(4), 3981-3988; doi:10.3390/molecules17043981
Received: 19 March 2012 / Revised: 30 March 2012 / Accepted: 31 March 2012 / Published: 2 April 2012
Cited by 3 | PDF Full-text (285 KB) | HTML Full-text | XML Full-text
Abstract
Oral administration of β-carotene (BC) was found to exert opposite effects on plasma levels of vascular endothelial growth factor (VEGF) in two animal models. One study in nude mice injected via tail vein with hepatocarcinoma SK-Hep-1 cells showed that BC decreases the [...] Read more.
Oral administration of β-carotene (BC) was found to exert opposite effects on plasma levels of vascular endothelial growth factor (VEGF) in two animal models. One study in nude mice injected via tail vein with hepatocarcinoma SK-Hep-1 cells showed that BC decreases the plasma VEGF level, whereas the other study in nude mice injected subcutaneously with prostate tumor PC-3 cells showed that BC increases the plasma VEGF level. Herein we investigated whether BC (0.5–20 μM) possesses diverse effects on VEGF secretion in SK-Hep-1, PC-3 and melanoma B16F10 cells. We found that incubation of SK-Hep-1 cells with BC (1–20 μM) for 6 h significantly decreased VEGF secretion, whereas BC (1–10 μM) significantly increased the VEGF secretion in PC-3 cells. However, these effects disappeared at 12 h of incubation. Similar effects occurred in VEGF mRNA and protein expression after treatment of SK-Hep-1 and PC-3 cells with BC for 6 h. In contrast, BC (0.5–20 μM) did not affect mRNA and protein expression and secretion of VEGF in B16F10 cells. We also found that the proliferation of SK-Hep-1 and B16F10 cells was significantly inhibited by 20 μM BC at 6 and 12 h of incubation, whereas the proliferation of PC-3 cells was significantly inhibited by 20 μM BC at 12 h of incubation. In summary, the present study demonstrated the tumor-specific effect of BC on VEGF secretion in different cancer cell lines. Full article
(This article belongs to the Special Issue Carotenoids)
Open AccessArticle Pressurized Hot Ethanol Extraction of Carotenoids from Carrot By-Products
Molecules 2012, 17(2), 1809-1818; doi:10.3390/molecules17021809
Received: 30 November 2011 / Revised: 26 January 2012 / Accepted: 1 February 2012 / Published: 10 February 2012
Cited by 22 | PDF Full-text (691 KB)
Abstract
Carotenoids are known for their antioxidant activity and health promoting effects. One of the richest sources of carotenoids are carrots. However, about 25% of the annual production is regarded as by-products due to strict market policies. The aim of this study was [...] Read more.
Carotenoids are known for their antioxidant activity and health promoting effects. One of the richest sources of carotenoids are carrots. However, about 25% of the annual production is regarded as by-products due to strict market policies. The aim of this study was to extract carotenoids from those by-products. Conventional carotenoid extraction methods require the use of organic solvents, which are costly, environmentally hazardous, and require expensive disposal procedures. Pressurized liquid extraction (PLE) utilizes conventional solvents at elevated temperatures and pressure, and it requires less solvent and shorter extraction times. The extraction solvent of choice in this study was ethanol, which is a solvent generally recognized as safe (GRAS). The extraction procedure was optimized by varying the extraction time (2–10 min) and the temperature (60–180 °C). β-Carotene was used as an indicator for carotenoids content in the carrots. The results showed that time and temperatures of extraction have significant effect on the yield of carotenoids. Increasing the flush volume during extraction did not improve the extractability of carotenoids, indicating that the extraction method was mainly desorption/diffusion controlled. Use of a dispersing agent that absorbs the moisture content was important for the efficiency of extraction. Analysing the content of β-carotene at the different length of extraction cycles showed that about 80% was recovered after around 20 min of extraction. Full article
(This article belongs to the Special Issue Carotenoids)
Open AccessArticle Carotenoids of Lettuce (Lactuca sativa L.) Grown on Soil Enriched with Spent Coffee Grounds
Molecules 2012, 17(2), 1535-1547; doi:10.3390/molecules17021535
Received: 5 December 2011 / Revised: 28 January 2012 / Accepted: 3 February 2012 / Published: 7 February 2012
Cited by 22 | PDF Full-text (249 KB)
Abstract
The impact of spent coffee grounds on carotenoid and chlorophyll content in lettuce (Lactuca sativa L. var. capitata) was evaluated. A greenhouse pot experiment was conducted with spent coffee amounts ranging from 0% to 20% (v/v). All evaluated pigments increased [...] Read more.
The impact of spent coffee grounds on carotenoid and chlorophyll content in lettuce (Lactuca sativa L. var. capitata) was evaluated. A greenhouse pot experiment was conducted with spent coffee amounts ranging from 0% to 20% (v/v). All evaluated pigments increased proportionally to spent coffee amounts. Lutein and β-carotene levels increased up to 90% and 72%, respectively, while chlorophylls increased up to 61%. Biomass was also improved in the presence of 2.5% to 10% spent coffee, decreasing for higher amounts. Nevertheless, all plants were characterized by lower organic nitrogen content than the control ones, inversely to the spent coffee amounts, pointing to possible induced stress. Collected data suggests that plants nutritional features, with regards to these bioactive compounds, can be improved by the presence of low amounts of spent coffee grounds (up to 10%). This observation is particularly important because soil amendment with spent coffee grounds is becoming increasingly common within domestic agriculture. Still, further studies on the detailed influence of spent coffee bioactive compounds are mandatory, particularly regarding caffeine. Full article
(This article belongs to the Special Issue Carotenoids)
Open AccessArticle Novel Cationic Carotenoid Lipids as Delivery Vectors of Antisense Oligonucleotides for Exon Skipping in Duchenne Muscular Dystrophy
Molecules 2012, 17(2), 1138-1148; doi:10.3390/molecules17021138
Received: 25 October 2011 / Revised: 22 December 2011 / Accepted: 4 January 2012 / Published: 24 January 2012
Cited by 10 | PDF Full-text (1278 KB)
Abstract
Duchenne Muscular Dystrophy (DMD) is a common, inherited, incurable, fatal muscle wasting disease caused by deletions that disrupt the reading frame of the DMD gene such that no functional dystrophin protein is produced. Antisense oligonucleotide (AO)-directed exon skipping restores the reading frame [...] Read more.
Duchenne Muscular Dystrophy (DMD) is a common, inherited, incurable, fatal muscle wasting disease caused by deletions that disrupt the reading frame of the DMD gene such that no functional dystrophin protein is produced. Antisense oligonucleotide (AO)-directed exon skipping restores the reading frame of the DMD gene, and truncated, yet functional dystrophin protein is expressed. The aim of this study was to assess the efficiency of two novel rigid, cationic carotenoid lipids, C30-20 and C20-20, in the delivery of a phosphorodiamidate morpholino (PMO) AO, specifically designed for the targeted skipping of exon 45 of DMD mRNA in normal human skeletal muscle primary cells (hSkMCs). The cationic carotenoid lipid/PMO-AO lipoplexes yielded significant exon 45 skipping relative to a known commercial lipid, 1,2-dimyristoyl-sn-glycero-3-ethylphosphocholine (EPC). Full article
(This article belongs to the Special Issue Carotenoids)
Figures

Open AccessArticle The Metal Cation Chelating Capacity of Astaxanthin. Does This Have Any Influence on Antiradical Activity?
Molecules 2012, 17(1), 1039-1054; doi:10.3390/molecules17011039
Received: 30 November 2011 / Revised: 16 December 2011 / Accepted: 5 January 2012 / Published: 20 January 2012
Cited by 5 | PDF Full-text (1227 KB) | Supplementary Files
Abstract
In this Density Functional Theory study, it became apparent that astaxanthin (ASTA) may form metal ion complexes with metal cations such as Ca+2, Cu+2, Pb+2, Zn+2, Cd+2 and Hg+2. The presence [...] Read more.
In this Density Functional Theory study, it became apparent that astaxanthin (ASTA) may form metal ion complexes with metal cations such as Ca+2, Cu+2, Pb+2, Zn+2, Cd+2 and Hg+2. The presence of metal cations induces changes in the maximum absorption bands which are red shifted in all cases. Therefore, in the case of compounds where metal ions are interacting with ASTA, they are redder in color. Moreover, the antiradical capacity of some ASTA-metal cationic complexes was studied by assessing their vertical ionization energy and vertical electron affinity, reaching the conclusion that metal complexes are slightly better electron donors and better electron acceptors than ASTA. Full article
(This article belongs to the Special Issue Carotenoids)
Open AccessArticle The Effect of β-Carotene Supplementation on the Pharmacokinetics of Nelfinavir and Its Active Metabolite M8 in HIV-1-infected Patients
Molecules 2012, 17(1), 688-702; doi:10.3390/molecules17010688
Received: 9 December 2011 / Revised: 5 January 2012 / Accepted: 6 January 2012 / Published: 12 January 2012
Cited by 5 | PDF Full-text (285 KB)
Abstract
β-Carotene supplements are often taken by individuals living with HIV-1. Contradictory results from in vitro studies suggest that β-carotene may inhibit or induce cytochrome P450 enzymes and transporters. The study objective was to investigate the effect of β-carotene on the steady-state pharmacokinetics of nelfinavir and its active metabolite M8 in HIV-1 infected individuals. Twelve hour nelfinavir pharmacokinetic analysis was conducted at baseline and after 28 days of β-carotene supplementation (25,000 IU twice daily). Nelfinavir and M8 concentrations were measured with validated assays. Non-compartmental methods were used to calculate the pharmacokinetic parameters. Geometric mean ratios comparing day 28 to day 1 area under the plasma concentration-time curve (AUC0–12 h), maximum (Cmax) and minimum (Cmin) concentrations of nelfinavir and M8 are presented with 90% confidence intervals. Eleven subjects completed the study and were included in the analysis. There were no significant differences in nelfinavir AUC0–12 h and Cmin (−10%, +4%) after β-carotene supplementation. The M8 Cmin was increased by 31% while the M8 AUC0–12 h and Cmax were unchanged. During the 28 day period, mean CD4+ % and CD4+:CD8+ ratio increased significantly (p < 0.01). β-carotene supplementation increased serum carotene levels but did not cause any clinically significant difference in the nelfinavir and M8 exposure. Full article
(This article belongs to the Special Issue Carotenoids)
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Review

Jump to: Research

Open AccessReview Hydrophilic Carotenoids: Recent Progress
Molecules 2012, 17(5), 5003-5012; doi:10.3390/molecules17055003
Received: 22 March 2012 / Revised: 17 April 2012 / Accepted: 19 April 2012 / Published: 30 April 2012
Cited by 3 | PDF Full-text (305 KB)
Abstract
Carotenoids are substantially hydrophobic antioxidants. Hydrophobicity is this context is rather a disadvantage, because their utilization in medicine as antioxidants or in food chemistry as colorants would require some water dispersibility for their effective uptake or use in many other ways. In [...] Read more.
Carotenoids are substantially hydrophobic antioxidants. Hydrophobicity is this context is rather a disadvantage, because their utilization in medicine as antioxidants or in food chemistry as colorants would require some water dispersibility for their effective uptake or use in many other ways. In the past 15 years several attempts were made to synthetize partially hydrophilic carotenoids. This review compiles the recently synthetized hydrophilic carotenoid derivatives. Full article
(This article belongs to the Special Issue Carotenoids)
Open AccessReview Dynamic Action of Carotenoids in Cardioprotection and Maintenance of Cardiac Health
Molecules 2012, 17(4), 4755-4769; doi:10.3390/molecules17044755
Received: 6 February 2012 / Revised: 28 March 2012 / Accepted: 5 April 2012 / Published: 23 April 2012
Cited by 19 | PDF Full-text (339 KB) | HTML Full-text | XML Full-textRetraction
Abstract
Oxidative stress has been considered universally and undeniably implicated in the pathogenesis of all major diseases, including those of the cardiovascular system. Oxidative stress activate transcriptional messengers, such as nuclear factor—κB, tangibly contributing to endothelial dysfunction, the initiation and progression of atherosclerosis, [...] Read more.
Oxidative stress has been considered universally and undeniably implicated in the pathogenesis of all major diseases, including those of the cardiovascular system. Oxidative stress activate transcriptional messengers, such as nuclear factor—κB, tangibly contributing to endothelial dysfunction, the initiation and progression of atherosclerosis, irreversible damage after ischemic reperfusion, and even arrhythmia, such as atrial fibrillation. Evidence is rapidly accumulating to support the role of reactive oxygen species (ROS) and reactive nitrogen species (RNS) as intracellular signaling molecules. Despite this connection between oxidative stress and cardiovascular disease (CVD), there are currently no recognized therapeutic interventions to address this important unmet need. Antioxidants that provide a broad, “upstream” approach via ROS/RNS quenching or free radical chain breaking seem an appropriate therapeutic option based on epidemiologic, dietary, and in vivo animal model data. Short-term dietary intervention trials suggest that diets rich in fruit and vegetable intake lead to improvements in coronary risk factors and reduce cardiovascular mortality. Carotenoids are such abundant, plant-derived, fat-soluble pigments that functions as antioxidants. They are stored in the liver or adipose tissue, and are lipid soluble by becoming incorporated into plasma lipoprotein particles during transport. For these reasons, carotenoids may represent one plausible mechanism by which fruits and vegetables reduce the risk of chronic diseases as cardiovascular disease (CVD). This review paper outlines the role of carotenoids in maintaining cardiac health and cardioprotection mediated by several mechanisms including redox signaling. Full article
(This article belongs to the Special Issue Carotenoids)
Open AccessReview Cancer Chemoprevention by Carotenoids
Molecules 2012, 17(3), 3202-3242; doi:10.3390/molecules17033202
Received: 22 December 2011 / Revised: 15 February 2012 / Accepted: 6 March 2012 / Published: 14 March 2012
Cited by 107 | PDF Full-text (684 KB)
Abstract
Carotenoids are natural fat-soluble pigments that provide bright coloration to plants and animals. Dietary intake of carotenoids is inversely associated with the risk of a variety of cancers in different tissues. Preclinical studies have shown that some carotenoids have potent antitumor effects [...] Read more.
Carotenoids are natural fat-soluble pigments that provide bright coloration to plants and animals. Dietary intake of carotenoids is inversely associated with the risk of a variety of cancers in different tissues. Preclinical studies have shown that some carotenoids have potent antitumor effects both in vitro and in vivo, suggesting potential preventive and/or therapeutic roles for the compounds. Since chemoprevention is one of the most important strategies in the control of cancer development, molecular mechanism-based cancer chemoprevention using carotenoids seems to be an attractive approach. Various carotenoids, such as β-carotene, a-carotene, lycopene, lutein, zeaxanthin, β-cryptoxanthin, fucoxanthin, canthaxanthin and astaxanthin, have been proven to have anti-carcinogenic activity in several tissues, although high doses of β-carotene failed to exhibit chemopreventive activity in clinical trials. In this review, cancer prevention using carotenoids are reviewed and the possible mechanisms of action are described. Full article
(This article belongs to the Special Issue Carotenoids)
Open AccessReview Key to Xenobiotic Carotenoids
Molecules 2012, 17(3), 2877-2928; doi:10.3390/molecules17032877
Received: 9 January 2012 / Revised: 21 February 2012 / Accepted: 22 February 2012 / Published: 7 March 2012
Cited by 3 | PDF Full-text (519 KB)
Abstract
A listing of carotenoids with heteroatoms (X = F, Cl, Br, I, Si, N, S, Se, Fe) directly attached to the carotenoid carbon skeleton has been compiled. The 178 listed carotenoids with C,H,X atoms demonstrate that the classical division of carotenoids into [...] Read more.
A listing of carotenoids with heteroatoms (X = F, Cl, Br, I, Si, N, S, Se, Fe) directly attached to the carotenoid carbon skeleton has been compiled. The 178 listed carotenoids with C,H,X atoms demonstrate that the classical division of carotenoids into hydrocarbon carotenoids (C,H) and xanthophylls (C,H,O) has become obsolete. Full article
(This article belongs to the Special Issue Carotenoids)
Open AccessReview Mechanisms of Suppression and Enhancement of Photocurrent/Conversion Efficiency in Dye-Sensitized Solar-Cells Using Carotenoid and Chlorophyll Derivatives as Sensitizers
Molecules 2012, 17(2), 2188-2218; doi:10.3390/molecules17022188
Received: 10 December 2011 / Revised: 14 February 2012 / Accepted: 15 February 2012 / Published: 22 February 2012
Cited by 8 | PDF Full-text (2252 KB)
Abstract
The mechanisms of suppression and enhancement of photocurrent/conversion efficiency (performance) in dye-sensitized solar cells, using carotenoid and chlorophyll derivatives as sensitizers, were compared systematically. The key factor to enhance the performance was found to be how to minimize interaction among the excited-state [...] Read more.
The mechanisms of suppression and enhancement of photocurrent/conversion efficiency (performance) in dye-sensitized solar cells, using carotenoid and chlorophyll derivatives as sensitizers, were compared systematically. The key factor to enhance the performance was found to be how to minimize interaction among the excited-state dye-sensitizer(s). In a set of retinoic-acid (RA) and carotenoic-acid (CA) sensitizers, having n conjugated double bonds, CA7 gave rise to the highest performance, which was reduced toward RA5 and CA13. The former was ascribed to the generation of triplet and the resultant singlet-triplet annihilation reaction, while the latter, to the intrinsic electron injection efficiency. In a set of shorter polyene sensitizers having different polarizabilities, the one with the highest polarizability (the highest trend of aggregate formation) exhibited the higher performance toward the lower dye concentration and the lower light intensity, contrary to our expectation. This is ascribed to a decrease in the singlet-triplet annihilation reaction. The performance of cosensitization, by a pair of pheophorbide sensitizers without and with the central metal, Mg or Zn, was enhanced by the light absorption (complementary rather than competitive), the transition-dipole moments (orthogonal rather than parallel) and by the pathways of electron injection (energetically independent rather than interactive). Full article
(This article belongs to the Special Issue Carotenoids)
Open AccessReview Reaction Dynamics of Flavonoids and Carotenoids as Antioxidants
Molecules 2012, 17(2), 2140-2160; doi:10.3390/molecules17022140
Received: 4 January 2012 / Revised: 30 January 2012 / Accepted: 3 February 2012 / Published: 21 February 2012
Cited by 29 | PDF Full-text (410 KB)
Abstract
Flavonoids and carotenoids with rich structural diversity are ubiquitously present in the plant kingdom. Flavonoids, and especially their glycosides, are more hydrophilic than most carotenoids. The interaction of flavonoids with carotenoids occurs accordingly at water/lipid interfaces and has been found important for [...] Read more.
Flavonoids and carotenoids with rich structural diversity are ubiquitously present in the plant kingdom. Flavonoids, and especially their glycosides, are more hydrophilic than most carotenoids. The interaction of flavonoids with carotenoids occurs accordingly at water/lipid interfaces and has been found important for the functions of flavonoids as antioxidants in the water phase and especially for the function of carotenoids as antioxidants in the lipid phase. Based on real-time kinetic methods for the fast reactions between (iso)flavonoids and radicals of carotenoids, antioxidant synergism during protection of unsaturated lipids has been found to depend on: (i) the appropriate distribution of (iso)flavonoids at water/lipid interface, (ii) the difference between the oxidation potentials of (iso)flavonoid and carotenoid and, (iii) the presence of electron-withdrawing groups in the carotenoid for facile electron transfer. For some (unfavorable) combinations of (iso)flavonoids and carotenoids, antioxidant synergism is replaced by antagonism, despite large potential differences. For contact with the lipid phase, the lipid/water partition coefficient is of importance as a macroscopic property for the flavonoids, while intramolecular rotation towards coplanarity upon oxidation by the carotenoid radical cation has been identified by quantum mechanical calculations to be an important microscopic property. For carotenoids, anchoring in water/lipid interface by hydrophilic groups allow the carotenoids to serve as molecular wiring across membranes for electron transport. Full article
(This article belongs to the Special Issue Carotenoids)
Open AccessReview Astaxanthin in Cardiovascular Health and Disease
Molecules 2012, 17(2), 2030-2048; doi:10.3390/molecules17022030
Received: 18 January 2012 / Revised: 13 February 2012 / Accepted: 13 February 2012 / Published: 20 February 2012
Cited by 29 | PDF Full-text (289 KB)
Abstract
Oxidative stress and inflammation are established processes contributing to cardiovascular disease caused by atherosclerosis. However, antioxidant therapies tested in cardiovascular disease such as vitamin E, C and β-carotene have proved unsuccessful at reducing cardiovascular events and mortality. Although these outcomes may reflect [...] Read more.
Oxidative stress and inflammation are established processes contributing to cardiovascular disease caused by atherosclerosis. However, antioxidant therapies tested in cardiovascular disease such as vitamin E, C and β-carotene have proved unsuccessful at reducing cardiovascular events and mortality. Although these outcomes may reflect limitations in trial design, new, more potent antioxidant therapies are being pursued. Astaxanthin, a carotenoid found in microalgae, fungi, complex plants, seafood, flamingos and quail is one such agent. It has antioxidant and anti-inflammatory effects. Limited, short duration and small sample size studies have assessed the effects of astaxanthin on oxidative stress and inflammation biomarkers and have investigated bioavailability and safety. So far no significant adverse events have been observed and biomarkers of oxidative stress and inflammation are attenuated with astaxanthin supplementation. Experimental investigations in a range of species using a cardiac ischaemia-reperfusion model demonstrated cardiac muscle preservation when astaxanthin is administered either orally or intravenously prior to the induction of ischaemia. Human clinical cardiovascular studies using astaxanthin therapy have not yet been reported. On the basis of the promising results of experimental cardiovascular studies and the physicochemical and antioxidant properties and safety profile of astaxanthin, clinical trials should be undertaken. Full article
(This article belongs to the Special Issue Carotenoids)
Open AccessReview The Role of Carotenoids in Human Skin
Molecules 2011, 16(12), 10491-10506; doi:10.3390/molecules161210491
Received: 17 November 2011 / Revised: 3 December 2011 / Accepted: 8 December 2011 / Published: 16 December 2011
Cited by 25 | PDF Full-text (213 KB)
Abstract
The human skin, as the boundary organ between the human body and the environment, is under the constant influence of free radicals (FR), both from the outside in and from the inside out. Carotenoids are known to be powerful antioxidant substances playing [...] Read more.
The human skin, as the boundary organ between the human body and the environment, is under the constant influence of free radicals (FR), both from the outside in and from the inside out. Carotenoids are known to be powerful antioxidant substances playing an essential role in the reactions of neutralization of FR (mainly reactive oxygen species ROS). Carotenoid molecules present in the tissue are capable of neutralizing several attacks of FR, especially ROS, and are then destroyed. Human skin contains carotenoids, such as α-, γ-, β-carotene, lutein, zeaxanthin, lycopene and their isomers, which serve the living cells as a protection against oxidation. Recent studies have reported the possibility to investigate carotenoids in human skin quickly and non-invasively by spectroscopic means. Results obtained from in-vivo studies on human skin have shown that carotenoids are vital components of the antioxidative protective system of the human skin and could serve as marker substances for the overall antioxidative status. Reflecting the nutritional and stress situation of volunteers, carotenoids must be administered by means of antioxidant-rich products, e.g., in the form of fruit and vegetables. Carotenoids are degraded by stress factors of any type, inter alia, sun radiation, contact with environmental hazards, illness, etc. The kinetics of the accumulation and degradation of carotenoids in the skin have been investigated. Full article
(This article belongs to the Special Issue Carotenoids)

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