Photo Protection of Haematococcus pluvialis Algae by Astaxanthin: Unique Properties of Astaxanthin Deduced by EPR, Optical and Electrochemical Studies

Effect of Light of Different Spectral Compositions on Pro/Antioxidant Status, Content of Some Pigments and Secondary Metabolites and Expression of Related Genes in Scots Pine

The aim of this study was to investigate the effect of light quality (white fluorescent light, WFL, containing UV components), red light (RL, 660 nm), blue light (BL, 450 nm), and white LED light (WL, 450 + 580 nm) on the components of the cellular antioxidant system in Pinus sylvestris L. in needles, roots, and hypocotyls, focusing on the accumulation of key secondary metabolites and the expression of related genes. The qualitative and quantitative composition of carotenoids; the content of the main photosynthetic pigments, phenolic compounds, flavonoids (catechins, proanthocyanidins, anthocyanins), ascorbate, and glutathione; the activity of the main antioxidant enzymes; the content of hydrogen peroxide; and the intensity of lipid peroxidation (MDA and 4-HNE contents) were determined. RL resulted in an increase in the content of hydrogen peroxide and 4-HNE, as well as the total fraction of flavonoids in the needles. It also enhanced the expression of several PR (pathogen-related) genes compared to BL and WL. WFL increased the content of phenols, including flavonoids, and enhanced the overall activity of low-molecular antioxidants in needles and hypocotyls. BL increased the content of ascorbate and glutathione, including reduced glutathione, in the needles and simultaneously decreased the activity of peroxidases. Thus, by modifying the light quality, it is possible to regulate the accumulation of secondary metabolites in pine roots and needles, thereby influencing their resistance to various biotic and abiotic stressors.

The Endless World of Carotenoids-Structural, Chemical and Biological Aspects of Some Rare Carotenoids

Carotenoids are a large and diverse group of compounds that have been shown to have a wide range of potential health benefits. While some carotenoids have been extensively studied, many others have not received as much attention. Studying the physicochemical properties of carotenoids using electron paramagnetic resonance (EPR) and density functional theory (DFT) helped us understand their chemical structure and how they interact with other molecules in different environments. Ultimately, this can provide insights into their potential biological activity and how they might be used to promote health. In particular, some rare carotenoids, such as sioxanthin, siphonaxanthin and crocin, that are described here contain more functional groups than the conventional carotenoids, or have similar groups but with some situated outside of the rings, such as sapronaxanthin, myxol, deinoxanthin and sarcinaxanthin. By careful design or self-assembly, these rare carotenoids can form multiple H-bonds and coordination bonds in host molecules. The stability, oxidation potentials and antioxidant activity of the carotenoids can be improved in host molecules, and the photo-oxidation efficiency of the carotenoids can also be controlled. The photostability of the carotenoids can be increased if the carotenoids are embedded in a nonpolar environment when no bonds are formed. In addition, the application of nanosized supramolecular systems for carotenoid delivery can improve the stability and biological activity of rare carotenoids.

Carotenoids from Marine Sources as a New Approach in Neuroplasticity Enhancement

An increasing number of people experience disorders related to the central nervous system (CNS). Thus, new forms of therapy, which may be helpful in repairing processes' enhancement and restoring declined brain functions, are constantly being sought. One of the most relevant physiological processes occurring in the brain for its entire life is neuroplasticity. It has tremendous significance concerning CNS disorders since neurological recovery mainly depends on restoring its structural and functional organization. The main factors contributing to nerve tissue damage are oxidative stress and inflammation. Hence, marine carotenoids, abundantly occurring in the aquatic environment, being potent antioxidant compounds, may play a pivotal role in nerve cell protection. Furthermore, recent results revealed another valuable characteristic of these compounds in CNS therapy. By inhibiting oxidative stress and neuroinflammation, carotenoids promote synaptogenesis and neurogenesis, consequently presenting neuroprotective activity. Therefore, this paper focuses on the carotenoids obtained from marine sources and their impact on neuroplasticity enhancement.

Astaxanthin as a Novel Mitochondrial Regulator: A New Aspect of Carotenoids, beyond Antioxidants

Astaxanthin is a member of the carotenoid family that is found abundantly in marine organisms, and has been gaining attention in recent years due to its varied biological/physiological activities. It has been reported that astaxanthin functions both as a pigment, and as an antioxidant with superior free radical quenching capacity. We recently reported that astaxanthin modulated mitochondrial functions by a novel mechanism independent of its antioxidant function. In this paper, we review astaxanthin’s well-known antioxidant activity, and expand on astaxanthin’s lesser-known molecular targets, and its role in mitochondrial energy metabolism.

The neuroprotective potential of carotenoids in vitro and in vivo

BACKGROUND

Despite advances in research on neurodegenerative diseases, the pathogenesis and treatment response of neurodegenerative diseases remain unclear. Recent studies revealed a significant role of carotenoids to treat neurodegenerative diseases. The aim of this study was to systematically review the neuroprotective potential of carotenoids in vivo and in vitro and the molecular mechanisms and pathological factors contributing to major neurodegenerative diseases (Alzheimer's disease, Huntington's disease, Parkinson's disease, amyotrophic lateral sclerosis, and stroke).

HYPOTHESIS

Carotenoids as therapeutic molecules to target neurodegenerative diseases.

RESULTS

Aggregation of toxic proteins, mitochondrial dysfunction, oxidative stress, the excitotoxic pathway, and neuroinflammation were the major pathological factors contributing to the progression of neurodegenerative diseases. Furthermore, in vitro and in vivo studies supported the beneficiary role of carotenoids, namely lycopene, β-carotene, crocin, crocetin, lutein, fucoxanthin and astaxanthin in alleviating disease progression. These carotenoids provide neuroprotection by inhibition of neuro-inflammation, microglial activation, excitotoxic pathway, modulation of autophagy, attenuation of oxidative damage and activation of defensive antioxidant enzymes. Additionally, studies conducted on humans also demonstrated that dietary intake of carotenoids lowers the risk of neurodegenerative diseases.

CONCLUSION

Carotenoids may be used as drugs to prevent and treat neurodegenerative diseases. Although, the in vitro and in vivo results are encouraging, further well conducted clinical studies on humans are required to conclude about the full potential of neurodegenerative diseases.

E/Z isomerization of astaxanthin and its monoesters in vitro under the exposure to light or heat and in overilluminated Haematococcus pluvialis cells

Thermo- and photoisomerization of astaxanthin was investigated in a model system (solutions in methanol and chloroform), and the dynamics of astaxanthin isomers and esters content was analyzed in Haematococcus pluvialis green algal cells exposed to factors inducing astaxanthin accumulation. In both systems, the astaxanthin isomerization process seems to be defined by a) the action of light (or heat), and b) the dielectric constant of the surrounding medium. Upon heating, the accumulation of Z-isomers occurred in a model system during the entire incubation period. For the first 5 h of illumination, both Z-isomers accumulated in the solutions up to 5%, and then their content decreased. The accumulated amount of the Z-isomers in the cells of H. pluvialis was found to reach 42% of the total content of astaxanthin initially, and then it decreased during the experiment. The results lead to a conclusion that both cultivation of H. pluvialis culture in specific conditions and heat treatment of the resulting extracts from it might be efficient for obtaining large amounts of economically useful astaxanthin Z-isomer.

Gamma-aminobutyric acid facilitates the simultaneous production of biomass, astaxanthin and lipids in Haematococcus pluvialis under salinity and high-light stress conditions

The effects of γ-aminobutyric acid (GABA) on the biomass and astaxanthin and lipids production in Haematococcus pluvialis under combined salinity stress and high-light stresses were investigated. The results showed that the highest biomass (1.65 g L^-1), astaxanthin production (3.86 mg L^-1 d^-1) and lipids content (55.11%) in H. pluvialis LUGU were observed under the 0.25 mM GABA treatment. Moreover, compared with salinity and high-light stress, GABA treatment also increased the transcript levels of biosynthesis genes, the contents of endogenous GABA and carbohydrates but decreased reactive oxygen species (ROS) levels. Further evidence revealed that intracellular GABA could regulate cell growth, astaxanthin production and lipids synthesis by mediating carotenogenesis, lipogenesis and ROS signalling. Collectively, this study provides a combined strategy for promoting the coproduction of astaxanthin and lipids and sheds light on the regulatory mechanism through which GABA affects cell growth, astaxanthin production and lipids biosynthesis in H. pluvialis under unfavourable conditions.

Carotenoids: Importance in Daily Life-Insight Gained from EPR and ENDOR

Carotenoids are indispensable molecules for life. They are present everywhere in plants, algae, bacteria whom they protect against free radicals and oxidative stress. Through the consumption of fruits and vegetables and some carotenoid-containing fish, they are introduced into the human body and, similarly, protect it. There are numerous health benefits associated with the consumption of carotenoids. Carotenoids are antioxidants but at the same time they are prone to oxidation themselves. Electron loss from the carotenoid forms a radical cation. Furthermore, proton loss from a radical cation forms a neutral radical. In this mini-review, we discuss carotenoid radicals studied in our groups by various physicochemical methods, namely the radical cations formed by electron transfer and neutral radicals formed by proton loss from the radical cations. They contain many similar hyperfine couplings due to interactions between the electron spin and numerous protons in the carotenoid. Different EPR and ENDOR methods in combination with DFT calculations have been used to distinguish the two independent carotenoid radical species. DFT predicted larger coupling constants for the neutral radical compared to the radical cation. Previously, INDO calculations miss assigned the large couplings to the radical cation. EPR and ENDOR have aided in elucidating the physisorb, electron and proton transfer processes that occur when carotenoids are adsorbed on solid artificial matrices, and predicted similar reactions in aqueous solution or in plants. After years of study of the physicochemical properties of carotenoid radicals, the different published results start to merge together for a better understanding of carotenoid radical species and their implication in biological systems. Up until 2008, the radical chemistry in artificial systems was elucidated but the correlation between quenching ability and neutral radical formation was an inspiration to look for these radical species in vivo. In addition, the EPR spin-trapping technique has been applied to study inclusion complexes of carotenoids with different delivery systems.

Photooxidative stress-inducible orange and pink water-soluble astaxanthin-binding proteins in eukaryotic microalga

Lipid astaxanthin, a potent antioxidant known as a natural sunscreen, accumulates in eukaryotic microalgae and confers photoprotection. We previously identified a photooxidative stress-inducible water-soluble astaxanthin-binding carotenoprotein (AstaP) in a eukaryotic microalga (Coelastrella astaxanthina Ki-4) isolated from an extreme environment. The distribution in eukaryotic microalgae remains unknown. Here we identified three novel AstaP orthologs in a eukaryotic microalga, Scenedesmus sp. Oki-4N. The purified proteins, named AstaP-orange2, AstaP-pink1, and AstaP-pink2, were identified as secreted fasciclin proteins with potent 1O2 quenching activity in aqueous solution, which are characteristics shared with Ki-4 AstaP. Nonetheless, the absence of glycosylation in the AstaP-pinks, the presence of a glycosylphosphatidylinositol (GPI) anchor motif in AstaP-orange2, and highly acidic isoelectric points (pI = 3.6-4.7), differed significantly from that of AstaP-orange1 (pI = 10.5). These results provide unique examples on the use of water-soluble forms of astaxanthin in photosynthetic organisms as novel strategies for protecting single cells against severe photooxidative stresses.

Structures of Astaxanthin and Their Consequences for Therapeutic Application

Reactive oxygen species (ROS) are continuously generated as a by-product of normal aerobic metabolism. Elevated ROS formation leads to potential damage of biological structures and is implicated in various diseases. Astaxanthin, a xanthophyll carotenoid, is a secondary metabolite responsible for the red-orange color of a number of marine animals and microorganisms. There is mounting evidence that astaxanthin has powerful antioxidant, anti-inflammatory, and antiapoptotic activities. Hence, its consumption can result in various health benefits, with potential for therapeutic application. Astaxanthin contains both a hydroxyl and a keto group, and this unique structure plays important roles in neutralizing ROS. The molecule quenches harmful singlet oxygen, scavenges peroxyl and hydroxyl radicals and converts them into more stable compounds, prevents the formation of free radicals, and inhibits the autoxidation chain reaction. It also acts as a metal chelator and converts metal prooxidants into harmless molecules. However, like many other carotenoids, astaxanthin is affected by the environmental conditions, e.g., pH, heat, or exposure to light. It is hence susceptible to structural modification, i.e., via isomerization, aggregation, or esterification, which alters its physiochemical properties. Here, we provide a concise overview of the distribution of astaxanthin in tissues, and astaxanthin structures, and their role in tackling singlet oxygen and free radicals. We highlight the effect of structural modification of astaxanthin molecules on the bioavailability and biological activity. These studies suggested that astaxanthin would be a promising dietary supplement for health applications.

Morphological Change and Cell Disruption of Haematococcus pluvialis Cyst during High-Pressure Homogenization for Astaxanthin Recovery

Haematococcus pluvialis accumulates astaxanthin, which is a high-value antioxidant, during the red cyst stage of its lifecycle. The development of a rigid cell wall in the cysts hinders the recovery of astaxanthin. We investigated morphological changes and cell disruption of mature H. pluvialis cyst cells while using high-pressure homogenization for astaxanthin extraction. When treated with French-press-cell (pressure, 10,000–30,000 psi; passage, 1–3), the intact cyst cells were significantly broken or fully ruptured, releasing cytoplasmic components, thereby facilitating the separation of astaxanthin by ethyl acetate. Fluorescence microscopy observations using three different fluorescent dyes revealed that a greater degree of cell breakage caused greater external dispersion of astaxanthin, chlorophyll, lipids, proteins, and carbohydrates. The mechanical treatment resulted in a high cell disruption rate of up to 91% based on microscopic cell typing and Coulter methods. After the ethyl acetate extraction, the astaxanthin concentration significantly increased by 15.2 mg/L in proportion to the increase in cell disruption rate, which indicates that cell disruption is a critical factor for solvent-based astaxanthin recovery. Furthermore, this study recommends a synergistic combination of the fast instrumental particle-volume-distribution analysis and microscope-based morphologic phenotyping for the development of practical H. pluvialis biorefinery processes that co-produce various biological products, including lipids, proteins, carbohydrates, chlorophyll, and astaxanthin.

In-Vitro Antioxidant Properties of Lipophilic Antioxidant Compounds from 3 Brown Seaweed

Lipophilic compounds of seaweed have been linked to their potential bioactivity. Low polarity solvents such as chloroform, diethyl ether, n-hexane and their various combinations were used to extract the lipophilic antioxidants from brown seaweed namely Himanthalia elongata, Laminaria saccharina and Laminaria digitata. An equal-volume mixture of chloroform, diethyl ether and n-hexane (Mix 4) gave the highest total phenol (52.7 ± 1.93 to 180.2 ± 1.84 mg gallic acid equivalents/g), flavonoid (31.9 ± 2.65 to 131.3 ± 4.51 mg quercetin equivalents/g), carotenoid (2.19 ± 1.37 to 3.15 ± 0.91 μg/g) and chlorophyll content (2.88 ± 1.08 to 3.86 ± 1.22 μg/g) in the tested seaweeds. The extracts were screened for their potential antioxidant capacity and the extracts obtained from the selected solvents system exhibited the highest radical scavenging capacity against 2,2′-diphenly-1-picrylhydrazyl radical (EC₅₀ 98.3 ± 2.78 to 298.8 ± 5.81 mg/L) and metal ions (EC₅₀ 228.6 ± 3.51 to 532.4 ± 6.03 mg/L). Similarly, the same extract showed the highest ferric reducing antioxidant power (8.3 ± 0.23 to 26.3 ± 0.30 mg trolox equivalents/g) in all the seaweeds. Rapid characterization of the active extracts by liquid chromatography coupled with photodiode array detector and electrospray ionization tandem mass spectrometry (LC-PDA–ESI-MS/MS) identified cyanidin-3-O-glucoside, fucoxanthin, violaxanthin, β-carotene, chlorophyll a derivatives and chlorophyll b derivatives in the tested seaweed. The study demonstrated the use of tested brown seaweed as potential species to be considered for future applications in medicine, cosmetics and as nutritional food supplement.

Storage of Carotenoids in Crustaceans as an Adaptation to Modulate Immunopathology and Optimize Immunological and Life-History Strategies

Why do some invertebrates store so much carotenoids in their tissues? Storage of carotenoids may not simply be passive and dependent on their environmental availability, as storage variation exists at various taxonomic scales, including among individuals within species. While the strong antioxidant and sometimes immune-stimulating properties of carotenoids may be beneficial enough to cause the evolution of features improving their assimilation and storage, they may also have fitness downsides explaining why massive carotenoid storage is not universal. Here, the functional and ecological implications of carotenoid storage for the evolution of invertebrate innate immune defenses are examined, especially in crustaceans, which massively store carotenoids for unclear reasons. Three testable hypotheses about the role of carotenoid storage in immunological (resistance and tolerance) and life-history strategies (with a focus on aging) are proposed, which may ultimately explain the storage of large amounts of these pigments in a context of host-pathogen interactions.

The carotenoid Bixin found to exhibit the highest measured carotenoid oxidation potential to date consistent with its practical protective use in cosmetics, drugs and food

The electrochemical oxidation potentials of cis bixin correspond to the production of the carotenoid radical cation, Car⁺ and dication Car⁺⁺. The oxidation is a two-electron process with oxidation potentials at ~0.94 and ~1.14 V vs SCE (reference to ferrocene at 0.528 V) in THF. These potentials are higher than that of symmetrical canthaxanthin at 0.775 V and 0.972 V and for β-carotene at 0.634 V and 0.605 V respectively. The second oxidation potential for canthaxanthin is higher by 0.20 V than the first. Similar difference is observed for bixin. In contrast, the second oxidation potential for β-carotene is lower by 30 mV than that of the first. Reduction potentials were found to occur at ~-0.69 and ~-1.22 V vs SCE. The lifetime of the radical cation of cis bixin, Car⁺, is short and decays rapidly at ambient temperature. The suggested scavenging ability of cis bixin towards reactive oxidative oxygen species is estimated to be 44. On the other hand, that of β-carotene, symmetrical canthaxanthin and the dicyano substituted carotenoid which exhibit oxidation potentials of 0.634 V, 0.775 V and 0.833 V vs SCE were measured to be 0.64, 1.96 and 23.60 respectively. The non-reversible electrochemical measurements suggest the tendency for bixin to react with trace amounts of reactive oxygen species (OH, O₂^-, OOH).

Carotenoids-Antioxidant Properties

The carotenoid group of pigments are ubiquitous in nature and more than 600 different carotenoids have been identified and characterized [1].[...].