Cyclic endoperoxides of β-carotene, potential pro-oxidants, as products of chemical quenching of singlet oxygen

Research on carbon black and cerium co-doped Ti4O7-CB-Ce electrocatalytic oxidation of tetracycline-based antibiotics

Elemental doping is a promising way for enhancing the electrocatalytic activity of metal oxides. Herein, we fabricate Ti/ Ti4O7-CB-Ce anode materials by the modification means of carbon black and cerium co-doped Ti4O7, and this shift effectively improves the interfacial charge transfer rate of Ti4O7 and •OH yield in the electrocatalytic process. Remarkably, the Ti4O7-CB-Ce anode exhibits excellent efficiency of minocycline (MNC) wastewater treatment (100% removal within 20 min), and the removal rate reduces from 100 to 98.5% after five cycles, which is comparable to BDD electrode. •OH and 1O2 are identified as the active species in the reaction. Meanwhile, it is discovered that Ti/ Ti4O7-CB-Ce anodes can effectively improve the biochemical properties of the non-biodegradable pharmaceutical wastewater (B/C values from 0.25 to 0.44) and significantly reduce the toxicity of the wastewater (luminescent bacteria inhibition rate from 100 to 26.6%). This work paves an effective strategy for designing superior metal oxides electrocatalysts.

Gardenia yellow pigment: Extraction methods, biological activities, current trends, and future prospects

Food coloring plays a vital role in influencing consumers' food choices, imparting vibrant and appealing colors to various food and beverage products. Synthetic food colorants have been the most commonly used coloring agents in the food industry. However, concerns about potential health issues related to synthetic colorants, coupled with increasing consumer demands for food safety and health, have led food manufacturers to explore natural alternatives. Natural pigments not only offer a wide range of colors to food products but also exhibit beneficial bioactive properties. Gardenia yellow pigment is a water-soluble natural pigment with various biological activities, widely present in gardenia fruits. Therefore, this paper aims to delve into Gardenia Yellow Pigment, highlighting its significance as a food colorant. Firstly, a thorough understanding and exploration of various methods for obtaining gardenia yellow pigment. Subsequently, the potential functionality of gardenia yellow pigment was elaborated, especially its excellent antioxidant and neuroprotective properties. Finally, the widespread application trend of gardenia yellow pigment in the food industry was explored, as well as the challenges faced by the future development of gardenia yellow pigment in the field of food and health. Some feasible solutions were proposed, providing valuable references and insights for researchers, food industry professionals, and policy makers.

The Association between Malaria and β-Carotene Levels: A Systematic Review and Meta-Analysis

BACKGROUND

β-Carotene, which is a prominent carotenoid with notable antioxidant properties, may play a role in countering the oxidative stresses induced by malaria. The association between β-carotene levels and malaria is not yet fully understood, prompting this systematic review and meta-analysis.

METHODS

A rigorous search of databases, including Nursing and Allied Health Premium, EMBASE, MEDLINE, Ovid, PubMed, Scopus, and Google Scholar, was undertaken to collate studies that focused on β-carotene levels in malaria patients. The selected studies underwent critical appraisal, followed by data extraction for a meta-analysis.

RESULTS

Of the 2498 records initially identified, 10 were deemed suitable for synthesis. A considerable number of these studies indicated a pronounced reduction in β-carotene levels among malaria patients in contrast with uninfected individuals. The meta-analysis, encompassing 421 malaria patients and 240 uninfected controls, revealed a significant correlation between reduced β-carotene levels and malaria (p < 0.01, Hedges's g: -1.26, 95% CI: -2.00-(-0.53), I2: 93.86%, seven studies).

CONCLUSIONS

The conducted systematic review and meta-analysis corroborated the correlation between lower β-carotene levels and malaria. The intricate relationship between malaria and β-carotene merits deeper exploration. A comprehensive understanding of this association might pave the way for innovative therapeutic approaches leveraging the antioxidant attributes of β-carotene to combat malaria-induced oxidative stress.

β-carotene-loaded nanoparticles protect against neuromotor damage, oxidative stress, and dopamine deficits in a model of Parkinson's disease in Drosophila melanogaster

β-carotene-loaded nanoparticles improves absorption by increasing bioavailability. The Drosophila melanogaster model of Parkinson's disease must be helpful in investigating potential neuroprotective effects. Four groups of four-day-old flies were exposed to: (1) control; (2) diet containing rotenone (500 μM); (3) β-carotene-loaded nanoparticles (20 μM); (4) β-carotene-loaded nanoparticles and rotenone for 7 days. Then, the percentage of survival, geotaxis tests, open field, aversive phototaxis and food consumption were evaluated. At the end of the behaviors, the analyses of the levels of reactive species (ROS), thiobarbituric acid reactive substances (TBARS), catalase (CAT) and superoxide dismutase (SOD) activity was carried out, as well as an evaluation of the levels of dopamine and acetylcholinesterase (AChE) activity, in the head of flies. Nanoparticles loaded with β-carotene were able to improve motor function, memory, survival and also restored the oxidative stress indicators (CAT, SOD, ROS and TBARS), dopamine levels, AChE activity after exposure to rotenone. Overall, nanoparticles loaded with β-carotene showed significant neuroprotective effect against damage induced by the Parkinson-like disease model, emerging as a possible treatment. Overall, β-carotene-loaded nanoparticles presented significant neuroprotective effect against damage induced by model of Parkinson-like disease, emerging as a possible treatment.

Antioxidants encapsulated milk-derived exosomes for functional food development

Reactive oxygen species are known to be involved in various diseases, and antioxidant ingredients are expected to essentially prevent diseases and contribute to improving health. However, antioxidants are easily degraded by enzymes before being absorbed in the intestine, so a means of transport that prevents their degradation in the body is necessary. Exosomes, which play an important role in communication between individual cells, have attracted attention as a new transport carrier of miRNA and DNA, but not yet fully exploited in food research. More recently, exosomes extracted from bovine milk began to be widely used as a cost-effective transport carrier not in clinical medicine but also in functional food materials. To develop practical applications as carriers for functional foods, systematic studies are necessary to clarify the introduction efficiency and the properties of encapsulated substances. In this study, we applied electroporation and incubation to encapsulate antioxidants into the exosomes and studied the encapsulation efficiency into the exosomes and the anticancer activity.

Phytochemical Analysis and Demonstration of Antioxidant, Antibacterial, and Antibiofilm Activities of Ethnomedicinal Plants of North East India

Ethnomedicinal plants are a rich reservoir of active compounds with potent pharmacological properties. Therefore, plants could serve as a source for the discovery of active antimicrobial and antioxidant agents and are focused because of their low toxicity, economic viability, easy availability, etc. In this regard, phytochemical analyses, viz. β-carotene, total sugar, reducing sugar, vitamin C, total carotenoids, protein, total phenolic content (TPC), and total flavonoid content (TFC) of 20 ethnomedicinal plants of North East India (NEI) were evaluated in this study. The antibacterial activity against human pathogens and antioxidant potential of plant extracts was also demonstrated. The minimum inhibitory concentration (MIC₈₀), minimum bactericidal concentration (MBC), and total antibacterial activity (TAA) of the active extracts were evaluated against Pseudomonas aeruginosa and Chromobacterium violaceum. The active extracts were also examined for antibiofilm as well as anti-pyocyanin activities against P. aeruginosa and anti-QS activity against C. violaceum at sub-MICs. The study demonstrated variable concentration of phytochemicals of the extracts, viz. β-carotene (0.29-8.91 mg g^-1), total sugar (2.92-30.6 mM), reducing sugar (0.44-14.5 mM), vitamin C (8.41-31.3 mg g^-1), total carotenoids (14.9-267.0 mg g^-1), protein (5.65-283 mg g^-1), TPC (5.32-31.0 mg GAE/g DW), and TFC (1.74-68.2 mg QE/g DW). The plant extracts also exhibited potent antioxidant and antibacterial activities against both Gram-positive and Gram-negative bacteria. Some of the extracts also demonstrated significant biofilm inhibition and eradication, anti-pyocyanin, and anti-QS activities at sub-MICs. The selected ethnomedicinal plants are rich in phytochemicals and demonstrated potent antioxidant, antibacterial, and antibiofilm activities, thus could serve as the important source of novel antioxidant and antimicrobial agents.

Theoretical study on the mechanism and kinetics of the formation β-carotene epoxides from the oxidative degradation of β-carotene

Some factors such as oxidation can significantly affect the level of β-carotene after processing and during the storage of foods. Oxidative degradation of β-carotene with the active forms of oxygen produces β-carotene 5,6 and 5,8-epoxides. Two mechanisms involving a direct attack on the double bonds of the β-carotene by ¹O₂ (a neutral mechanism) and ³O₂ (a radical mechanism) oxygen have been proposed and considered kinetically and thermodynamically by the density functional theory method. It concluded that due to the smaller energy barrier in the first step, the neutral mechanism with ¹O₂ is a more desirable path than the diradical mechanism with ³O₂ and this was in complete agreement with the experimental reality of more reactivity of ¹O₂. The energy barriers of the stepwise manner in the intersystem crossing pathway showed a more favorable pathway in the neutral mechanism. The deviation of spin contamination values was ignorable in the diradical mechanism.

The Effect of β-Carotene, Tocopherols and Ascorbic Acid as Anti-Oxidant Molecules on Human and Animal In Vitro/In Vivo Studies: A Review of Research Design and Analytical Techniques Used

Prolonged elevated oxidative stress (OS) possesses negative effect on cell structure and functioning, and is associated with the development of numerous disorders. Naturally occurred anti-oxidant compounds reduce the oxidative stress in living organisms. In this review, antioxidant properties of β-carotene, tocopherols and ascorbic acid are presented based on in vitro, in vivo and populational studies. Firstly, environmental factors contributing to the OS occurrence and intracellular sources of Reactive Oxygen Species (ROS) generation, as well as ROS-mediated cellular structure degradation, are introduced. Secondly, enzymatic and non-enzymatic mechanism of anti-oxidant defence against OS development, is presented. Furthermore, ROS-preventing mechanisms and effectiveness of β-carotene, tocopherols and ascorbic acid as anti-oxidants are summarized, based on studies where different ROS-generating (oxidizing) agents are used. Oxidative stress biomarkers, as indicators on OS level and prevention by anti-oxidant supplementation, are presented with a focus on the methods (spectrophotometric, fluorometric, chromatographic, immuno-enzymatic) of their detection. Finally, the application of Raman spectroscopy and imaging as a tool for monitoring the effect of anti-oxidant (β-carotene, ascorbic acid) on cell structure and metabolism, is proposed. Literature data gathered suggest that β-carotene, tocopherols and ascorbic acid possess potential to mitigate oxidative stress in various biological systems. Moreover, Raman spectroscopy and imaging can be a valuable technique to study the effect of oxidative stress and anti-oxidant molecules in cell studies.

Is There an Optimal Combination of AREDS2 Antioxidants Zeaxanthin, Vitamin E and Vitamin C on Light-Induced Toxicity of Vitamin A Aldehyde to the Retina?

Vitamins C and E and zeaxanthin are components of a supplement tested in a large clinical trial-Age-Related Eye Disease Study 2 (AREDS2)-and it has been demonstrated that they can inhibit the progression of age-related macular degeneration. The aim of this study was to determine the optimal combinations of these antioxidants to prevent the phototoxicity mediated by vitamin A aldehyde (ATR), which can accumulate in photoreceptor outer segments (POS) upon exposure to light. We used cultured retinal pigment epithelial cells ARPE-19 and liposomes containing unsaturated lipids and ATR as a model of POS. Cells and/or liposomes were enriched with lipophilic antioxidants, whereas ascorbate was added just before the exposure to light. Supplementing the cells and/or liposomes with single lipophilic antioxidants had only a minor effect on phototoxicity, but the protection substantially increased in the presence of both ways of supplementation. Combinations of zeaxanthin with α-tocopherol in liposomes and cells provided substantial protection, enhancing cell viability from ~26% in the absence of antioxidants to ~63% in the presence of 4 µM zeaxanthin and 80 µM α-tocopherol, and this protective effect was further increased to ~69% in the presence of 0.5 mM ascorbate. The protective effect of ascorbate disappeared at a concentration of 1 mM, whereas 2 mM of ascorbate exacerbated the phototoxicity. Zeaxanthin or α-tocopherol partly ameliorated the cytotoxic effects. Altogether, our results suggest that the optimal combination includes upper levels of zeaxanthin and α-tocopherol achievable by diet and/or supplementations, whereas ascorbate needs to be at a four-fold smaller concentration than that in the vitreous. The physiological relevance of the results is discussed.

Triplet-driven chemical reactivity of β-carotene and its biological implications

The endoperoxides of β-carotene (βCar-EPOs) are regarded as main products of the chemical deactivation of ¹O₂ by β-carotene, one of the most important antioxidants, following a concerted singlet-singlet reaction. Here we challenge this view by showing that βCar-EPOs are formed in the absence of ¹O₂ in a non-concerted triplet-triplet reaction: ³O₂ + ³β-carotene → βCar-EPOs, in which ³β-carotene manifests a strong biradical character. Thus, the reactivity of β-carotene towards oxygen is governed by its excited triplet state. βCar-EPOs, while being stable in the dark, are photochemically labile, and are a rare example of nonaromatic endoperoxides that release ¹O₂, again not in a concerted reaction. Their light-induced breakdown triggers an avalanche of free radicals, which accounts for the pro-oxidant activity of β-carotene and the puzzling swap from its anti- to pro-oxidant features. Furthermore, we show that βCar-EPOs, and carotenoids in general, weakly sensitize ¹O₂. These findings underlie the key role of the triplet state in determining the chemical and photophysical features of β-carotene. They shake up the prevailing models of carotenoid photophysics, the anti-oxidant functioning of β-carotene, and the role of ¹O₂ in chemical signaling in biological photosynthetic systems. βCar-EPOs and their degradation products are not markers of ¹O₂ and oxidative stress but of the overproduction of extremely hazardous chlorophyll triplets in photosystems. Hence, the chemical signaling of overexcitation of the photosynthetic apparatus is based on a ³chlorophyll-³β-carotene relay, rather than on extremely short-lived ¹O₂.

Use of Gas Chromatography-Mass Spectrometry Techniques (GC-MS, GC-MS/MS and GC-QTOF) for the Characterization of Photooxidation and Autoxidation Products of Lipids of Autotrophic Organisms in Environmental Samples

This paper reviews applications of gas chromatography-mass spectrometry techniques for the characterization of photooxidation and autoxidation products of lipids of senescent phototrophic organisms. Particular attention is given to: (i) the selection of oxidation products that are sufficiently stable under environmental conditions and specific to each lipid class and degradation route; (ii) the description of electron ionization mass fragmentation of trimethylsilyl derivatives of these compounds; and (iii) the use of specific fragment ions for monitoring the oxidation of the main unsaturated lipid components of phototrophs. The techniques best geared for this task were gas chromatography-quadrupole-time of flight to monitor fragment ions with very high resolution and accuracy, and gas chromatography-tandem mass spectrometry to monitor very selective transitions in multiple reaction monitoring mode. The extent of the degradation processes can only be estimated if the oxidation products are unaffected by fast secondary oxidation reactions, as it is notably the case of ∆5-sterols, monounsaturated fatty acids, chlorophyll phytyl side-chain, and di- and triterpenoids. In contrast, the primary degradation products of highly branched isoprenoid alkenes possessing more than one trisubstituted double bond, alkenones, carotenoids and polyunsaturated fatty acids, appear to be too unstable with respect to secondary oxidation or other reactions to serve for quantification in environmental samples.

Naturally Occurring Antioxidant Therapy in Alzheimer's Disease

It is estimated that the prevalence rate of Alzheimer's disease (AD) will double by the year 2040. Although currently available treatments help with symptom management, they do not prevent, delay the progression of, or cure the disease. Interestingly, a shared characteristic of AD and other neurodegenerative diseases and disorders is oxidative stress. Despite profound evidence supporting the role of oxidative stress in the pathogenesis and progression of AD, none of the currently available treatment options address oxidative stress. Recently, attention has been placed on the use of antioxidants to mitigate the effects of oxidative stress in the central nervous system. In preclinical studies utilizing cellular and animal models, natural antioxidants showed therapeutic promise when administered alone or in combination with other compounds. More recently, the concept of combination antioxidant therapy has been explored as a novel approach to preventing and treating neurodegenerative conditions that present with oxidative stress as a contributing factor. In this review, the relationship between oxidative stress and AD pathology and the neuroprotective role of natural antioxidants from natural sources are discussed. Additionally, the therapeutic potential of natural antioxidants as preventatives and/or treatment for AD is examined, with special attention paid to natural antioxidant combinations and conjugates that are currently being investigated in human clinical trials.

Exploring the Diversity and Regulation of Apocarotenoid Metabolic Pathways in Plants

In plants, carotenoids are subjected to enzyme-catalyzed oxidative cleavage reactions as well as to non-enzymatic degradation processes, which produce various carbonyl products called apocarotenoids. These conversions control carotenoid content in different tissues and give rise to apocarotenoid hormones and signaling molecules, which play important roles in plant growth and development, response to environmental stimuli, and in interactions with surrounding organisms. In addition, carotenoid cleavage gives rise to apocarotenoid pigments and volatiles that contribute to the color and flavor of many flowers and several fruits. Some apocarotenoid pigments, such as crocins and bixin, are widely utilized as colorants and additives in food and cosmetic industry and also have health-promoting properties. Considering the importance of this class of metabolites, investigation of apocarotenoid diversity and regulation has increasingly attracted the attention of plant biologists. Here, we provide an update on the plant apocarotenoid biosynthetic pathway, especially highlighting the diversity of the enzyme carotenoid cleavage dioxygenase 4 (CCD4) from different plant species with respect to substrate specificity and regioselectivity, which contribute to the formation of diverse apocarotenoid volatiles and pigments. In addition, we summarize the regulation of apocarotenoid metabolic pathway at transcriptional, post-translational, and epigenetic levels. Finally, we describe inter- and intraspecies variation in apocarotenoid production observed in many important horticulture crops and depict recent progress in elucidating the genetic basis of the natural variation in the composition and amount of apocarotenoids. We propose that the illustration of biochemical, genetic, and evolutionary background of apocarotenoid diversity would not only accelerate the discovery of unknown biosynthetic and regulatory genes of bioactive apocarotenoids but also enable the identification of genetic variation of causal genes for marker-assisted improvement of aroma and color of fruits and vegetables and CRISPR-based next-generation metabolic engineering of high-value apocarotenoids.

Influence of the Bioactive Diet Components on the Gene Expression Regulation

Diet bioactive components, in the concept of nutrigenetics and nutrigenomics, consist of food constituents, which can transfer information from the external environment and influence gene expression in the cell and thus the function of the whole organism. It is crucial to regard food not only as the source of energy and basic nutriments, crucial for living and organism development, but also as the factor influencing health/disease, biochemical mechanisms, and activation of biochemical pathways. Bioactive components of the diet regulate gene expression through changes in the chromatin structure (including DNA methylation and histone modification), non-coding RNA, activation of transcription factors by signalling cascades, or direct ligand binding to the nuclear receptors. Analysis of interactions between diet components and human genome structure and gene activity is a modern approach that will help to better understand these relations and will allow designing dietary guidances, which can help maintain good health.

Quenching effects of (-)-Epigallocatechin gallate for singlet oxygen production and its protection against oxidative damage induced by Ce6-mediated photodynamic therapy in vitro

BACKGROUND

Singlet oxygen (¹O₂) is highly reactive to biological components such as lipids, proteins and DNA, which induces oxidative damage to cells and tissues. Natural antioxidants may function as ¹O₂ quencher to prevent ¹O₂ involved photosensitized oxidation in biological system.

METHODS

Time-resolved measurement of ¹O₂ luminescence was employed to evaluate the ¹O₂ quenching abilities of natural antioxidants in air-statured phosphate buffered saline (PBS), including (-)-Epigallocatechin gallate (EGCG), Proanthocyanidins, L-carnosine and Vitamin C. The ¹O₂ quenching effects and rate constant of EGCG were investigated by detecting the absorption, fluorescence and ¹H-NMR spectroscopy and ¹O₂ luminescence decay curves, respectively. In addition, the protective activity of EGCG against ¹O₂ oxidative damage caused by Ce6-mediated photodynamic therapy (PDT) was verified in cells.

RESULTS

EGCG, proanthocyanidins, L-carnosine and Vitamin C efficiently quenched ¹O₂ luminescence at 1270 nm. The triplet-state quenching rate constants of EGCG for Rose Bengal (RB), Chlorin e6, AlPcS and HiPorfin are 2.21 × 10⁹, 4.90 × 10⁸, 3.30 × 10⁸, 1.78 × 10⁹ M^-1s^-1, while the ¹O₂ quenching rate constants are 2.80 × 10⁸, 1.50 × 10⁸, 1.30 × 10⁸, 1.70 × 10⁸ M^-1s^-1, respectively. Furthermore, EGCG could effectively quench ¹O₂ production to prevent NIH/3T3 cells oxidative damage induced by Ce6-mediated PDT.

CONCLUSIONS

EGCG is an efficient quencher for both triplet-state photosensitizers and ¹O₂. The quenching ability of EGCG during photosensitization for selected photosensitizers is: RB > HiPorfin > Ce6 > AlPcS. EGCG could be used to protect normal cells and tissue against oxidative damage.

Molecular insights into the endoperoxide formation by Fe(II)/α-KG-dependent oxygenase NvfI

Endoperoxide-containing natural products are a group of compounds with structurally unique cyclized peroxide moieties. Although numerous endoperoxide-containing compounds have been isolated, the biosynthesis of the endoperoxides remains unclear. NvfI from Aspergillus novofumigatus IBT 16806 is an endoperoxidase that catalyzes the formation of fumigatonoid A in the biosynthesis of novofumigatonin. Here, we describe our structural and functional analyses of NvfI. The structural elucidation and mutagenesis studies indicate that NvfI does not utilize a tyrosyl radical in the reaction, in contrast to other characterized endoperoxidases. Further, the crystallographic analysis reveals significant conformational changes of two loops upon substrate binding, which suggests a dynamic movement of active site during the catalytic cycle. As a result, NvfI installs three oxygen atoms onto a substrate in a single enzyme turnover. Based on these results, we propose a mechanism for the NvfI-catalyzed, unique endoperoxide formation reaction to produce fumigatonoid A.

Development of a free radical scavenging bacterial consortium to mitigate oxidative stress in cnidarians

Corals are colonized by symbiotic microorganisms that profoundly influence the animal’s health. One noted symbiont is a single‐celled alga (in the dinoflagellate family Symbiodiniaceae), which provides the coral with most of its fixed carbon. Thermal stress increases the production of reactive oxygen species (ROS) by Symbiodiniaceae during photosynthesis. ROS can both damage the algal symbiont’s photosynthetic machinery and inhibit its repair, causing a positive feedback loop for the toxic accumulation of ROS. If not scavenged by the antioxidant network, excess ROS may trigger a signaling cascade ending with the coral host and algal symbiont disassociating in a process known as bleaching. We use Exaiptasia diaphana as a model for corals and constructed a consortium comprised of E. diaphana–associated bacteria capable of neutralizing ROS. We identified six strains with high free radical scavenging (FRS) ability belonging to the families Alteromonadaceae, Rhodobacteraceae, Flavobacteriaceae and Micrococcaceae. In parallel, we established a consortium of low FRS isolates consisting of genetically related strains. Bacterial whole genome sequences were used to identify key pathways that are known to influence ROS.

β-Carotene-Induced Alterations in Haemoglobin Affinity to O2

β-Carotene (β-Crt) can be dispersed in hydrophobic regions of the membrane of red blood cells (RBC). Its location, orientation and distribution strongly depend on carotenoid concentration. In the present pilot trial (six human subjects involved), it is demonstrated that incubation of RBCs with β-Crt (1.8 × 107 β-Crt molecules per RBC, 50 μmol/L) results in expansion of the membrane of RBCs and slight elongation of the cell. The changes are of statistical significance, as verified by the Wilcoxon test at p < 0.05. They indicate (i) a highly random orientation and location of β-Crt inside the membrane and (ii) a tendency for its interaction with membrane skeleton proteins. The accompanying effect of decreased RBC resistance to lysis is possibly a result of the incorrect functioning of ion channels due to their modification/disruption. At higher β-Crt concentrations, its clustering inside membranes may occur, leading to further alterations in the shape and size of RBCs, with the most pronounced changes observed at 1.8 × 108 β-Crt molecules per RBC (500 μmol/L). Due to the reduced permeability of ions, such membranes exhibit increased resistance to haemolysis. Finally, we show that interactions of β-Crt with the membrane of RBCs lead to an alteration in haemoglobin-oxygen affinity, shifting the oxyhaemoglobin dissociation curve toward higher oxygen partial pressures. If the impact of β-Crt on a curve course is confirmed in vivo, one may consider its role in the fine tuning of O2 transportation to tissues. Hence, at low concentrations, providing unchanged elastic and functional properties of RBCs, it could serve as a beneficial agent in optimising heart performance and cardiovascular load.

Singlet oxygen oxidation products of carotenoids, fatty acids and phenolic prenyllipids

Singlet oxygen (¹O₂) is the major reactive oxygen species ROS causing photooxidative stress in plants which is formed predominantly in the reaction center of photosystem II during photosynthesis. To avoid deleterious effects of ¹O₂ oxygen on photosynthetic membrane components, plant synthesize a variety of ¹O₂ quenchers of lipophilic character, such as carotenoids or phenolic prenyllipids (tocopherols, plastochromanol-8, plastoquinol). In the process of chemical quenching of ¹O₂ by the antioxidants, both short-lived products, such as oxidized carotenoids, or relative long-lived compounds, such as oxidized phenolic prenyllipids are formed. The other target of ¹O₂ are unsaturated fatty acids of membrane lipids that undergo peroxidation as a result of the reaction. Some of the ¹O₂ oxidation products, like β-cyclocitral can be components of ¹O₂-signallingsignaling pathway leading to acclimatory responses of plants, while some others further fulfill antioxidant functions, like hydroxy-plastochromanol or hydroxy-plastoquinol. As most of the ¹O₂ oxidation products are specific compounds formed only as a results of ¹O₂ action, they can be very useful, specific molecular markers of ¹O₂-dependent oxidative stress in vivo.

Plant apocarotenoids: from retrograde signaling to interspecific communication

Carotenoids are isoprenoid compounds synthesized by all photosynthetic and some non-photosynthetic organisms. They are essential for photosynthesis and contribute to many other aspects of a plant's life. The oxidative breakdown of carotenoids gives rise to the formation of a diverse family of essential metabolites called apocarotenoids. This metabolic process either takes place spontaneously through reactive oxygen species or is catalyzed by enzymes generally belonging to the CAROTENOID CLEAVAGE DIOXYGENASE family. Apocarotenoids include the phytohormones abscisic acid and strigolactones (SLs), signaling molecules and growth regulators. Abscisic acid and SLs are vital in regulating plant growth, development and stress response. SLs are also an essential component in plants' rhizospheric communication with symbionts and parasites. Other apocarotenoid small molecules, such as blumenols, mycorradicins, zaxinone, anchorene, β-cyclocitral, β-cyclogeranic acid, β-ionone and loliolide, are involved in plant growth and development, and/or contribute to different processes, including arbuscular mycorrhiza symbiosis, abiotic stress response, plant-plant and plant-herbivore interactions and plastid retrograde signaling. There are also indications for the presence of structurally unidentified linear cis-carotene-derived apocarotenoids, which are presumed to modulate plastid biogenesis and leaf morphology, among other developmental processes. Here, we provide an overview on the biology of old, recently discovered and supposed plant apocarotenoid signaling molecules, describing their biosynthesis, developmental and physiological functions, and role as a messenger in plant communication.

Pretreatment Dietary Patterns, Serum Carotenoids and Tocopherols Influence Tumor Immune Response in Head and Neck Squamous Cell Carcinoma

BACKGROUND

Tumor infiltrating lymphocytes (TILs) aid in informing treatment for head and neck squamous cell carcinoma (HNSCC). Nevertheless, little is known about the role of diet on TILs.

METHODS

Immunohistologic expression of CD4, CD8, CD68, CD103, CD104 and FOXP3 were assessed in tissue microarrays from 233 previously untreated HNSCC patients. Associations between these markers and pretreatment dietary patterns were evaluated using linear regression. Associations between baseline serum carotenoids, tocopherols and TILs were assessed using logistic regression. Cox models evaluated the association between diet and TILs on overall and recurrence-free survival.

RESULTS

Consumption of a Western dietary pattern was associated with lower CD8+ and FOXP3+ infiltrates (p-value:0.03 and 0.02, respectively). Multivariable logistic regression models demonstrated significantly higher CD8+ (OR:2.21;p-value:0.001) and FOXP3+ (OR:4.26;p-value:<0.0001) among patients with high gamma tocopherol. Conversely, high levels of xanthophylls (OR:0.12;p-value:<0.0001), lycopene (OR:0.36;p-value:0.0001) and total carotenoids(OR:0.31;p-value: <0.0001) were associated with significantly lower CD68+. Among those with high CD4+ (HR:1.77;p-value:0.03), CD68+ (HR:2.42;p-value:0.004), CD103+ (HR:3.64;p-value:0.03) and FOXP3+ (HR:3.09;p-value:0.05), having a high Western dietary pattern increased the risk of overall mortality when compared to a low Western dietary pattern.

CONCLUSION

Dietary patterns and serum carotenoids may play an important role in modifying TILs, and ultimately, outcome after diagnosis with HNSCC.

Fluorescence-enhanced second harmonic normal Raman scattering in β-carotene

β-carotene, an important biomolecule from the carotenoid family, plays a vital role in biosystem, the characteristic features of electronic and vibrational spectra will shed light on its photophysical properties. Here, in-situ high pressure Raman spectra of β-carotene are measured up to 26 GPa. Two possible phase transitions are identified at about 7 GPa and 14 GPa, respectively, through analysis of the frequency-pressure relationships. In order to clarify the intensity changes of Raman bands, high pressure UV-Vis absorption measurements of β-carotene are conducted. Besides resonance Raman enhancement effect, a new mechanism, fluorescence enhancement of normal Raman scattering, is proposed, which provides new methods and approaches for Raman spectroscopy.

Ameliorating Effects of Natural Antioxidant Compounds on Female Infertility: a Review

The prevalence of female infertility cases has been increasing at a frightening rate, affecting approximately 48 million women across the world. However, oxidative stress has been recognized as one of the main mediators of female infertility by causing various reproductive pathologies in females such as endometriosis, PCOS, preeclampsia, spontaneous abortion, and unexplained infertility. Nowadays, concerned women prefer dietary supplements with antioxidant properties over synthetic drugs as a natural way to lessen the oxidative stress and enhance their fertility. Therefore, the current review is an attempt to explore the efficacy of various natural antioxidant compounds including vitamins, carotenoids, and plant polyphenols and also of some medicinal plants in improving the fertility status of females. Our summarization of recent findings in the current article would pave the way toward the development of new possible antioxidant therapy to treat infertility in females. Natural antioxidant compounds found in fruits, vegetables, and other dietary sources, alone or in combination with other antioxidants, were found to be effective in ameliorating the oxidative stress-mediated infertility problems in both natural and assisted reproductive settings. Numerous medicinal plants showed promising results in averting the various reproductive disorders associated with female infertility, suggesting a plant-based herbal medicine to treat infertility. Although optimum levels of natural antioxidants have shown favorable results, however, their excessive intake may have adverse health impacts. Therefore, larger well-designed, dose-response studies in humans are further warranted to incorporate natural antioxidant compounds into the clinical management of female infertility.

A multifocal approach towards understanding the complexities of carotenoid biosynthesis and accumulation in rice grains

Carotenoids are mostly C40 terpenoids that participate in several important functions in plants including photosynthesis, responses to various forms of stress, signal transduction and photoprotection. While the antioxidant potential of carotenoids is of particular importance for human health, equally important is the role of β-carotene as the precursor for vitamin A in the human diet. Rice, which contributes upto 40% of dietary energy for mankind, contains very low level of β-carotene, thereby making it an important crop for enhancing β-carotene accumulation in its grains and consequently targeting vitamin A deficiency. Biosynthesis of carotenoids in the endosperm of white rice is blocked at the first enzymatic step wherein geranylgeranyl diphosphate is converted to phytoene by the action of phytoene synthase (PSY). Strategies aimed at enhancing β-carotene levels in the endosperm of white rice identified Narcissus pseudonarcissus (npPSY) and bacterial CRT1 as the regulators of the carotenoid biosynthetic pathway in rice. Besides transcriptional regulation of PSY, posttranscriptional regulation of PSY expression by OR gene, molecular synergism between ε-LCY and β-LCY and epigenetic control of CRITSO through SET DOMAIN containing protein appear to be the other regulatory nodes which regulate carotenoid biosynthesis and accumulation in rice grains. In this review, we elucidate a comprehensive and deeper understanding of the regulatory mechanisms of carotenoid metabolism in crops that will enable us to identify an effective tool to alleviate carotenoid content in rice grains.

Why is Zeaxanthin the Most Concentrated Xanthophyll in the Central Fovea?

Diet-based xanthophylls (zeaxanthin and lutein) are conditionally essential polar carotenoids preferentially accreted in high concentrations (1 mM) to the central retina, where they have the capacity to impart unique physiologically significant biophysical biochemical properties implicated in cell function, rescue, and survival. Macular xanthophylls interact with membrane-bound proteins and lipids to absorb/attenuate light energy, modulate oxidative stress and redox balance, and influence signal transduction cascades implicated in the pathophysiology of age-related macular degeneration. There is exclusive transport, sequestration, and appreciable bioamplification of macular xanthophylls from the circulating carotenoid pool to the retina and within the retina to regions required for high-resolution sensory processing. The distribution of diet-based macular xanthophylls and the lutein metabolite meso-zeaxanthin varies considerably by retinal eccentricity. Zeaxanthin concentrations are 2.5-fold higher than lutein in the cone-dense central fovea. This is an ~20-fold increase in the molar ratio relative to eccentric retinal regions with biochemically detectable macular xanthophylls. In this review, we discuss how the differences in the specific properties of lutein and zeaxanthin could help explain the preferential accumulation of zeaxanthin in the most vulnerable region of the macula.

The origin of the dark S1 state in carotenoids: a comprehensive model

In carotenoids, by analogy to polyenes, the symmetry of the π-electron system is often invoked to explain their peculiar electronic features, in particular the inactivity of the S₀ → S₁ transition in one-photon excitation. In this review, we verify whether the molecular symmetry of carotenoids and symmetry of their π-electron system are supported in experimental and computational studies. We focus on spectroscopic techniques which are sensitive to the electron density distribution, including the X-ray crystallography, electronic absorption, two-photon techniques, circular dichroism, nuclear magnetic resonance, Stark and vibrational spectroscopies, and on this basis we seek for the origin of inactivity of the S₁ state. We come across no experimental and computational evidence for the symmetry effects and the existence of symmetry restrictions on the electronic states of carotenoids. They do not possess an inversion centre and the C_2h symmetry approximation of carotenoid structure is by no means justified. In effect, the application of symmetry rules (and notification) to the electronic states of carotenoids in this symmetry group may lead to a wrong interpretation of experimental data. This conclusion together with the results summarized in the review allows us to advance a consistent model that explains the inactivity of the S₀ → S₁ transition. Within this model, S₁ is never accessible from S₀ due to the negative synergy of (i) the contributions of double excitations of very low probability, which elevate S₁ energy, and (ii) a non-verticality of the S₀ → S₁ transition, due to the breaking of Born-Oppenheimer approximation. Certainly, our simple model requires a further experimental and theoretical verification.

Liquid Biopsies in Lung Cancer: Four Emerging Technologies and Potential Clinical Applications

Background: Liquid biopsies offer a promising alternative to tissue samples, providing non-invasive diagnostic approaches or serial monitoring of disease evolution. However, certain challenges remain, and the full potential of liquid biopsies has yet to be reached. Here we report several methodological approaches to interrogate liquid biopsies using circulating tumour cell (CTC) enumeration and characterisation, transcriptomics, Raman spectroscopy, and copy number instability (CNI) scores using blood samples of lung cancer (LC) patients. Methods: We choose LC; since it still is the most common cause of cancer-related mortality worldwide, and therefore there is a need for development of new non-invasive diagnostic/prognostic technologies. Changes in gene expression were assessed using RNA-seq, and in CTCs using ImageStream, an imaging flow-cytometer. CNI scores, from paired tissue/ctDNA were also explored. Raman spectroscopy was used to provide chemical fingerprints of plasma samples. Results: CTCs were detected in all LC patients (n = 10). We observed a significant increase in CTC levels in LC patients (n = 10) compared to controls (n = 21). A similar CNI was noted in the tissue and plasma of 2 patients, where higher CNI scores corresponded with poorer outcome. Significant changes in Raman spectra (carotenoid concentrations) were noted in LC patients (n = 20) compared to controls (n = 10). RNA-seq revealed differential expression of 21 genes between LC cases and controls in both LC tissue and blood samples. Conclusions: Liquid biopsies can potentially provide a more comprehensive picture of the disease compared to a single tissue biopsy. CTC enumeration is feasible and sensitive for LC patients. Molecular profiling of CTCs is also possible from total blood. CNI scores and Raman spectra require further investigation. Further work is being undertaken to explore these methods of detection in a larger LC cohort.

Anti-inflammatory Activity of β-Carotene, Lycopene and Tri-n-butylborane, a Scavenger of Reactive Oxygen Species

BACKGROUND/AIM

The polyene carotenoids β-carotene and lycopene are antioxidants that not only quench singlet oxygen but also inhibit lipid peroxidation. Tri-n-butyl borane (TBB) is used as an initiator for dental resin materials and is extremely reactive with oxygen and reactive oxygen species (ROS). This reactionability of TBB may be analogous to that of carotenoids with ROS. To clarify the biological activity of such ROS scavengers, we investigated the anti-inflammatory activity of β-carotene, lycopene and TBB in terms of the expression of RNA for lipopolysaccharide (LPS)-induced cyclooxygenase-2 (Cox2), nitric oxide synthase 2 (Nos2) and tumor necrosis factor-alpha (Tnfa), and mRNA expression and up-regulation of heme oxygenase 1 (Hmox1) mRNA in RAW264.7 cells.

MATERIALS AND METHODS

mRNA expression was investigated using real-time reverse transcriptase-polymerase chain reaction (PCR). The antioxidant activity of carotenoids was evaluated using the induction period method in the azobisisobutyronitrile or benzoyl peroxide-methyl methacrylate system.

RESULTS

Hmox1 mRNA, but not Cox2 and Nos2 mRNA, was up-regulated by 100 μM β-carotene and lycopene, and by 0.125% TBB. LPS-stimulated Cox2, Nos2 and Tnfa gene expression was inhibited by 50 μM β-carotene and lycopene, and by 0.5-1% TBB. Both β-carotene and lycopene had weak antioxidant activity, but β-carotene showed pro-oxidant activity at higher concentrations.

CONCLUSION

The anti-inflammatory activity of β-carotene, lycopene and TBB may be related to their ROS-scavenging activity. Additionally, the activity of carotenoids and TBB may be attributed to the electrophilicity of ROS-induced carotenoid intermediates and boranes, respectively. Their anti-inflammatory activity may be attributable to enhancement of the potency of the electrophile/antioxidant response element transcription system in view of their up-regulation of Hmox1 mRNA expression.

Physicochemical Properties of Lutein-Loaded Microcapsules and Their Uptake via Caco-2 Monolayers

Lutein is one of the most important carotenoids that can be utilized in foods as a natural pigment and nutraceutical ingredient to improve eye health. However, its utilization is limited due to its poor solubility. Chemically, the highly unsaturated structure of lutein makes it extremely susceptible to light, oxygen, heat, and pro-oxidants and therefore easily oxidized, decomposed or dissociated. In this study, we aimed to imbed natural lutein to improve its storage stability and enhance its water dispersibility. As two commonly studied water-soluble and water-insoluble food-grade surfactants, lecithin and sodium caseinate (NaCas) were chosen as the wall materials, and lutein-loaded lecithin microcapsules and NaCas microcapsules were prepared, the results revealed the lutein-loaded NaCas microcapsules not only exhibited better solubility and stability than those of lutein-loaded lecithin microcapsules, but also were more stable when stored at 4 °C, 25 °C, 37 °C. Moreover, the lutein-loaded NaCas microcapsules were more easily absorbed by the intestinal Caco-2 cells than natural lutein. Considering the dispersibility, stability and cell absorption effect, the NaCas-based microparticle is a potential carrier for lutein.

Side Methyl Groups Control the Conformation and Contribute to Symmetry Breaking of Isoprenoid Chromophores

Ab initio DFT computations reveal that the essential structural and photophysical features of the conjugated π-electron system of retinal and carotenoids are dictated by "innocent" methyl substituents. These methyl groups shape the conformation and symmetry of the isoprenoid chromophores by causing a sigmoidal distortion of the polyene skeleton and increasing its flexibility, which facilitates fitting to their binding pockets in proteins. Comparison of in vacuo conformations of the chromophores with their native (protein-bound) conformations showed, surprisingly, that the peripheral groups and interactions with the protein environment are much less significant than the methyl side groups in tuning their structural features. The methyl side groups also contribute to a loss of symmetry elements specific to linear polyenes. In effect, the symmetry-imposed restrictions on the chromophore electronic properties are disabled, which is of tremendous relevance to their photophysics. This is evidenced by their non-negligible permanent dipole moments and by the simulated and experimentally measured circular dichroism spectra, which necessarily reflect the chirality of the conjugated π-electron system.

In silico genotoxicity and carcinogenicity prediction for food-relevant secondary plant metabolites

Humans are exposed to thousands of different secondary plant metabolites which may have beneficial health effects, but numerous compounds may also have toxic potential. In the present study we have examined the genotoxic and carcinogenic potential of 609 food-relevant phytochemicals by using computer models for toxicity prediction. We developed a scoring method and combined the results of different models to increase the predictive power. A combination of the VEGA models SARpy, KNN, ISS, and CAESAR, and of the LAZAR model "Salmonella typhimurium" for genotoxicity prediction performed better than the single models regarding specificity and accuracy. Statistical evaluation of the combined model for carcinogenicity prediction was not possible due to the low number of substances suitable for model validation. The in silico results of the present exercise will be useful for priority setting purposes regarding future risk assessment of secondary plant metabolites. Based on our analysis, (-)-asimilobine, aloin, annoretine, chrysothrone, coptisine, elymoclavine, and thalicminine were predicted to be genotoxic with high probability and may therefore be selected for subsequent experimental genotoxicity testing. Moreover, the class of pyrrolizidine alkaloids is suggested to be a high priority subject for further studies as these substances have been predicted to be carcinogenic with high probability.

Carotenoid intake from natural sources and colorectal cancer: a systematic review and meta-analysis of epidemiological studies

Carotenoid intake from natural sources has been hypothesized to reduce the risk of colorectal cancer (CRC). The aim of this study was to systematically review the epidemiological evidence for the association between carotenoid intake from natural sources and CRC development. We carried out a systematic review and meta-analysis of epidemiological studies to investigate whether the intake of specific carotenoids from natural sources, as well as combined carotenoids, is associated with the risk of CRC overall and by anatomic subsite. A comprehensive literature search of MEDLINE and Scopus databases was performed. Twenty-two articles were identified from the literature search, of which 16 were case-control studies and 6 were cohort studies. In the random-effects meta-analysis of case-control and cohort studies, we found no association between the intake of individual and total carotenoids and the risk of CRC overall and by anatomic subsite. Overall, our findings do not support a significant association between intake of specific carotenoids from dietary sources, as well as combined carotenoids, and the risk of CRC overall and by anatomic subsite.

Singlet Oxygen and Free Radical Reactions of Retinoids and Carotenoids-A Review

We report on studies of reactions of singlet oxygen with carotenoids and retinoids and a range of free radical studies on carotenoids and retinoids with emphasis on recent work, dietary carotenoids and the role of oxygen in biological processes. Many previous reviews are cited and updated together with new data not previously reviewed. The review does not deal with computational studies but the emphasis is on laboratory-based results. We contrast the ease of study of both singlet oxygen and polyene radical cations compared to neutral radicals. Of particular interest is the switch from anti- to pro-oxidant behavior of a carotenoid with change of oxygen concentration: results for lycopene in a cellular model system show total protection of the human cells studied at zero oxygen concentration, but zero protection at 100% oxygen concentration.

Nonenzymatic β-Carotene Degradation in Provitamin A-Biofortified Crop Plants

Provitamin A biofortification, the provision of provitamin A carotenoids through agriculture, is regarded as an effective and sustainable intervention to defeat vitamin A deficiency, representing a global health problem. This food-based intervention has been questioned in conjunction with negative outcomes for smokers and asbestos-exposed populations of the CARET and ATBC trials in which very high doses of β-carotene were supplemented. The current notion that β-carotene cleavage products (apocarotenoids) represented the harmful agents is the basis of the here-presented research. We quantitatively analyzed numerous plant food items and concluded that neither the amounts of apocarotenoids nor β-carotene provided by plant tissues, be they conventional or provitamin A-biofortified, pose an increased risk. We also investigated β-carotene degradation pathways over time. This reveals a substantial nonenzymatic proportion of carotene decay and corroborates the quantitative relevance of highly oxidized β-carotene polymers that form in all plant tissues investigated.

Extraction, Identification and Photo-Physical Characterization of Persimmon (Diospyros kaki L.) Carotenoids

Carotenoid pigments were extracted and purified from persimmon fruits using accelerated solvent extraction (ASE). Eleven pigments were isolated and five of them were clearly identified as all-trans-violaxanthine, all-trans-lutein, all-trans-zeaxanthin all-trans-cryptoxanthin and all-trans-β-carotene. Absorption and fluorescence spectra were recorded. To evaluate the potential of ¹O₂ quenching of the purified carotenoids, we used a monocarboxylic porphyrin (P1COOH) as the photosensitizer to produce ¹O₂. The rate constants of singlet oxygen quenching (Kq) were determined by monitoring the near-infrared (1270 nm) luminescence of ¹O₂ produced by photosensitizer excitation. The lifetime of singlet oxygen was measured in the presence of increasing concentrations of carotenoids in hexane. Recorded Kq values show that all-trans-β-cryptoxanthin, all-trans-β-carotene, all-trans-lycopene and all-trans-zeaxanthin quench singlet oxygen in hexane efficiently (associated Kq values of 1.6 × 10⁸, 1.3 × 10⁸, 1.1 × 10⁸ and 1.1 × 10⁸ M^-1·s^-1, respectively). The efficiency of singlet oxygen quenching of β-cryptoxanthin can thus change the consideration that β-carotene and lycopene are the most efficient singlet oxygen quenchers acting as catalysts for deactivation of the harmful ¹O₂.

Carotenoids buffer the acute phase response on fever, sickness behavior, and rapid bill color change in zebra finches

Carotenoids are finite resources that animals can allocate to self-maintenance, attractiveness, or reproduction. Here we test how carotenoids affect the acute phase response (APR), an intense rapid systemic response characterized by fever, sickness behavior, and production of acute phase proteins, which serves to reduce pathogen persistence. We conducted a 2x2 factorial design experiment in captive adult male and female zebra finches (Taeniopygia guttata) to determine the effects of carotenoid supplementation on the intensity of the APR. We measured changes in feeding rate, activity level, and body temperature of the birds. We found that, relative to unsupplemented controls, carotenoid-supplemented birds exhibited less severe reductions in feeding and activity, smaller increases in body temperature, and lower circulating levels of haptoglobin (an acute phase protein) 24 h after inducing an APR. Among supplemented individuals, those with higher blood carotenoid levels exhibited a lower reduction in activity rate after 24 h. Forty-eight hours after APR induction, birds exhibited a significant decrease in plasma carotenoid levels and a decrease in bill hue, with less reduction in hue in carotenoid-supplemented individuals. These results demonstrate that carotenoids can alleviate several important behavioral and physiological effects of an APR and that bill color can change rapidly following induction of the costly APR immune defense. In particular, immune activation may have caused birds to preferentially draw down carotenoids from the bloodstream, ostensibly for use in health. Rapid bill color changes over a 48-hr period support growing evidence that bills may serve as short-term signals of health and condition.

Reaction and Scavenging Mechanism of β-Carotene and Zeaxanthin with Reactive Oxygen Species

In order to investigate chemical scavenging mechanism of singlet oxygen, superoxide anion radical, and hydroxyl radical by carotenoids, reaction products obtained by reacting β-carotene or zeaxanthin with singlet oxygen, superoxide anion radical, and hydroxyl radical were analyzed by LC/PDA ESI-MS, and ESR spectrometry. β-Carotene endoperoxides were identified as the major reaction products of β-carotene and singlet oxygen, while β-carotene epoxides were the major reaction products of β-carotene and superoxide anion or hydroxyl radical. Similar results to those for β-carotene were obtained with zeaxanthin.

ABA accumulation in water-stressed Citrus roots does not rely on carotenoid content in this organ

Sustained abscisic acid (ABA) accumulation in dehydrated citrus roots depends on the transport from aerial organs. Under this condition, the role of the β,β-carotenoids (ABA precursors) to the de novo synthesis of ABA in roots needs to be clarified since their low availability in this organ restricts its accumulation. To accomplish that, detached citrus roots were exposed to light (to increase their carotenoid content) and subsequently dehydrated (to trigger ABA accumulation). Stress imposition sharply decreased the pool of β,β-carotenoids but, unexpectedly, no concomitant rise in ABA content was observed. Contrastingly, roots of intact plants (with low levels of carotenoids) showed a similar decrease of ABA precursor together with a significant ABA accumulation. Furthermore, upon dehydration both types of roots showed similar upregulation of the key genes involved in biosynthesis of carotenoids and ABA (CsPSY3a; CsβCHX1; CsβCHX2; CsNCED1; CsNCED2), demonstrating a conserved transcriptional response triggered by water stress. Thus, the sharp decrease in root carotenoid levels in response to dehydration should be related to other stress-related signals instead of contributing to ABA biosynthesis. In summary, ABA accumulation in dehydrated-citrus roots largely relies on the presence of the aerial organs and it is independent of the amount of available root β,β-carotenoids.

Light Absorption and Energy Transfer in the Antenna Complexes of Photosynthetic Organisms

The process of photosynthesis is initiated by the capture of sunlight by a network of light-absorbing molecules (chromophores), which are also responsible for the subsequent funneling of the excitation energy to the reaction centers. Through evolution, genetic drift, and speciation, photosynthetic organisms have discovered many solutions for light harvesting. In this review, we describe the underlying photophysical principles by which this energy is absorbed, as well as the mechanisms of electronic excitation energy transfer (EET). First, optical properties of the individual pigment chromophores present in light-harvesting antenna complexes are introduced, and then we examine the collective behavior of pigment-pigment and pigment-protein interactions. The description of energy transfer, in particular multichromophoric antenna structures, is shown to vary depending on the spatial and energetic landscape, which dictates the relative coupling strength between constituent pigment molecules. In the latter half of the article, we focus on the light-harvesting complexes of purple bacteria as a model to illustrate the present understanding of the synergetic effects leading to EET optimization of light-harvesting antenna systems while exploring the structure and function of the integral chromophores. We end this review with a brief overview of the energy-transfer dynamics and pathways in the light-harvesting antennas of various photosynthetic organisms.

Reaction of Paprika Carotenoids, Capsanthin and Capsorubin, with Reactive Oxygen Species

The reaction of paprika carotenoids, capsanthin and capsorubin, with reactive oxygen species (ROS), such as superoxide anion radical (·O2(-)), hydroxyl radical (·OH), and singlet oxygen ((1)O2), was analyzed by LC/PDA ESI-MS and ESR spectrometry. Capsanthin formed both the 5,6-epoxide and 5,8-epoxide by reaction with ·O2(-) and ·OH. Furthermore, capsanthin also formed 5,6- and 5,8-endoperoxide on reaction with (1)O2. The same results were obtained in the case of capsanthin diacetate. On the other hand, capsorubin showed higher stability against these ROS. Capsorubin formed 7,8-epoxide on reaction with ·O2(-) and ·OH and 7,8-endoperoxide on reaction with (1)O2.

Effects of Molecular Symmetry on the Electronic Transitions in Carotenoids

The aim of this work is the verification of symmetry effects on the electronic absorption spectra of carotenoids. The symmetry breaking in cis-β-carotenes and in carotenoids with nonlinear π-electron system is of virtually no effect on the dark transitions in these pigments, in spite of the loss of the inversion center and evident changes in their electronic structure. In the cis isomers, the S2 state couples with the higher excited states and the extent of this coupling depends on the position of the cis bend. A confrontation of symmetry properties of carotenoids with their electronic absorption and IR and Raman spectra shows that they belong to the C1 or C2 but not the C2h symmetry group, as commonly assumed. In these realistic symmetries all the electronic transitions are symmetry-allowed and the absence of some transitions, such as the dark S0 → S1 transition, must have another physical origin. Most likely it is a severe deformation of the carotenoid molecule in the S1 state, unachievable directly from the ground state, which means that the Franck-Condon factors for a vertical S0 → S1 transition are negligible because the final state is massively displaced along the vibrational coordinates. The implications of our findings have an impact on the understanding of the photophysics and functioning of carotenoids.