Electron- and Energy-Transfer Properties of Hydrophilic Carotenoids (original) (raw)
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Antioxidant and Prooxidant Properties of Carotenoids
Archives of Biochemistry and Biophysics, 2001
The ability of dietary carotenoids such as -carotene and lycopene to act as antioxidants in biological systems is dependent upon a number of factors. While the structure of carotenoids, especially the conjugated double bond system, gives rise to many of the fundamental properties of these molecules, it also affects how these molecules are incorporated into biological membranes. This, in turn, alters the way these molecules interact with reactive oxygen species, so that the in vivo behavior may be quite different from that seen in solution. The effectiveness of carotenoids as antioxidants is also dependent upon their interaction with other coantioxidants, especially vitamins E and C. Carotenoids may, however, lose their effectiveness as antioxidants at high concentrations or at high partial pressures of oxygen. It is unlikely that carotenoids actually act as prooxidants in biological systems; rather they exhibit a tendency to lose their effectiveness as antioxidants.
The carotenoids as anti-oxidants — a review
Journal of Photochemistry and Photobiology B: Biology, 1997
Carotenoids are abundant in many fruit.,, and vegetables and they play diver~e roles in photobiology, photochemi~,try and medic;he. Thi~ review concerns the reactivity of carotenoidx with singlet oxygen and the interaction of carotenoids with a range of tree radical~. Mcchani~m.~ associated with the anti-and pro-oxidant behaviour of carotencids are discussed including carotenoid interactions v, ith other anti-oxidants. © 1997 Elsevier Science S.A.
Antioxidant and pro-oxidant activities of carotenoids and their oxidation products
Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association, 2018
Carotenoids are lipid soluble plant pigments that make part of human daily diet. These compounds are able to react with diverse reactive species and originate a myriad of oxidation products that have similar or even more reactivity than their parent compounds. These products may be short-chain carbonyl compounds and, the commonly designated, apo-carotenoids. The effects fo these products in the human body are not yet fully understood, but it is believed that they are intimately related with their oxidative potential. As so, carotenoids and their oxidation products have undeniable potential as bioactive compounds. However, the multifactorial elements that influence their activity/reactivity make really hard, or probably impossible, the task to classify them as anti- or pro-oxidant compounds. This manuscript provides a thorough review on the reactions of carotenoids with the most physiologically relevant reactive oxygen and nitrogen species, and scrutinizes the resulting oxidation pro...
Carotenoid radical chemistry and antioxidant/pro-oxidant properties
Archives of biochemistry …, 2004
The purpose of this review is to summarise the current state of knowledge of (i) the kinetics and mechanisms of radical reactions with carotenoids,(ii) the properties of carotenoid radicals, and (iii) the antioxidant/pro-oxidant properties of carotenoids.
Journal of the Science of Food and Agriculture, 2001
Reactive oxygen species are potentially damaging molecules. An important function of antioxidants is to intercept harmful triplet states, in order to prevent the formation of singlet oxygen, or to quench singlet oxygen directly. However, antioxidants are also reactive towards other active oxygen species such as the hydroxyl radical, the superoxide anion and the non-excited oxygen ground state in the presence of radical initiators. It is well known that¯avonoids and carotenoids show strong antioxidant properties. Polyenes and carotenoids are the best known among the compounds that quench singlet oxygen by ef®cient energy transfer. A large number of modi®ed, synthetic analogues and derivatives have been synthesised to prepare even better quenchers than the natural carotenoids. Phenols are also excellent chain-breaking antioxidants. Recently, many indigoid dyes (including bacterial indigoids) were studied, with the remarkable result that most, but not all, members of this class of chromophores quench singlet oxygen at the diffusion limit and some of them are excellent radical traps. It has been shown in this study that a quantitative assessment of antioxidant properties of avonoids, carotenoids, phenols and natural indigoids can be achieved using the following three assays: (1) oxygen pressure dependence; (2) peroxide formation; (3) singlet oxygen quenching. Reactivities towards both excited states and ground state radicals can be properly described by these assays. The remarkable role of b-carotene as an`unusual antioxidant' (Burton GW and Ingold KU, Science 224: 569±573 (1984)) in reactions using various oxygen pressures becomes clearer. The socalled`pro-oxidant effects' concern primarily the antioxidant itself and its degradation, since no or very little damage to the substrate occurs in this type of experiment. Three main categories of antioxidants may be classi®ed: (1) excellent antioxidants that perfectly quench excited states as well as ground state radicals (eg actinioerythrol, astaxanthin); (2) good antioxidants that strongly inhibit peroxide formation but are less ef®cient in quenching excited states (eg¯avonols, tocopherols) or lead to considerable degradation of the antioxidant itself (eg b-carotene, lycopene); (3) moderate antioxidants that fail to excel in both reactivities (eg z-carotene,¯avone).
Are dietary carotenoids beneficial? Reactions of carotenoids with oxy-radicals and singlet oxygen
Photochemical & Photobiological Sciences, 2004
Carotenoids play diverse roles in biology and medicine. Both the quenching of singlet oxygen (energy transfer) and interaction with oxy-radicals (electron transfer, H-atom transfer and addition reactions) are key processes in understanding many of these roles. Much previous work in 'simple' solvents is reviewed and new results in cell membrane models are presented. The possible consequences of using carotenoids as dietary supplements are discussed.
The effect of polarity of environment on the antioxidant activity of carotenoids
Chemical Physics Letters, 2020
Four density functionals and the C-PCM solvation model were used in the DFT calculations of the oxidation potentials of four carotenoids in cyclohexane, dichloromethane and water. The values obtained using M06-2X + D3 density functional fit the experimental data the best. The calculated oxidation potentials of the carotenoids decrease with increasing the polarities of the solvents, the difference being as large as 0.6 V. These behaviors are independent of the symmetries and chain lengths of the carotenoids. The results of this study are very important in the design of supramolecular carotenoid complexes because the antioxidant activities of carotenoids are oxidation potential dependent.
Potential Role of Carotenoids as Antioxidants in Human Health and Disease
Nutrients, 2014
Carotenoids constitute a ubiquitous group of isoprenoid pigments. They are very efficient physical quenchers of singlet oxygen and scavengers of other reactive oxygen species. Carotenoids can also act as chemical quenchers undergoing irreversible oxygenation. The molecular mechanisms underlying these reactions are still not fully understood, especially in the context of the anti-and pro-oxidant activity of carotenoids, which, although not synthesized by humans and animals, are also present in their blood and tissues, contributing to a number of biochemical processes. The antioxidant potential of carotenoids is of particular significance to human health, due to the fact that losing antioxidant-reactive oxygen species balance results in "oxidative stress", a critical factor of the pathogenic processes of various chronic disorders. Data coming from epidemiological studies and clinical trials strongly support the observation that adequate carotenoid supplementation may significantly reduce the risk of several disorders mediated by reactive oxygen species. Here, we would like to highlight the beneficial (protective) effects of dietary carotenoid intake in exemplary widespread modern civilization diseases, i.e., cancer, cardiovascular or photosensitivity disorders, in the context of carotenoids' unique antioxidative properties.
Carotenoids: Importance in Daily Life—Insight Gained from EPR and ENDOR
2021
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. Differe...
Antioxidant properties of carotenoids: QSAR prediction of their redox potentials
General Physiology and Biophysics
There is a great need to predict the antioxidant properties of molecules such as carotenoids. These compounds are of great interest due to their contribution to various important biological and industrial processes, including toxicity and fate. In our study, redox potentials were compiled from several literature sources. Redox potential values ranged from 537.2 mV for zeaxanthin up to 691.5 mV for β-carotene; they correspond to the formation of cation radicals, using the standard calomel electrode (SCE). The redox potential values were measured using conventional electrochemical techniques, cyclic voltammetry and Osteryoung square-wave voltammetry. A quantitative structureactivity relationship (QSAR) was developed to model and consequently to predict the values of redox potential. The predicted values of redox potential for four external carotenoids, namely β-carotene, zeaxanthin, cantaxanthin and astaxanthin, are presented and discussed. They indicate the dependence of redox potential on structure, donor and acceptor groups and polarisability.