Browsing by Author "Kispert, Lowell D."

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    Antioxidant Activity in Supramolecular Carotenoid Complexes Favored by Nonpolar Environment and Disfavored by Hydrogen Bonding
    (MDPI, 2020) Gao, Yunlong; Focsan, A. Ligia; Kispert, Lowell D.; Nanjing Agricultural University; University System of Georgia; Valdosta State University; University of Alabama Tuscaloosa
    Carotenoids are well-known antioxidants. They have the ability to quench singlet oxygen and scavenge toxic free radicals preventing or reducing damage to living cells. We have found that carotenoids exhibit scavenging ability towards free radicals that increases nearly exponentially with increasing the carotenoid oxidation potential. With the oxidation potential being an important parameter in predicting antioxidant activity, we focus here on the different factors affecting it. This paper examines how the chain length and donor/acceptor substituents of carotenoids affect their oxidation potentials but, most importantly, presents the recent progress on the effect of polarity of the environment and orientation of the carotenoids on the oxidation potential in supramolecular complexes. The oxidation potential of a carotenoid in a nonpolar environment was found to be higher than in a polar environment. Moreover, in order to increase the photostability of the carotenoids in supramolecular complexes, a nonpolar environment is desired and the formation of hydrogen bonds should be avoided.
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    Carotenoids: Importance in Daily Life-Insight Gained from EPR and ENDOR
    (Springer, 2021) Focsan, A. Ligia; Polyakov, Nikolay E.; Kispert, Lowell D.; Valdosta State University; Voevodsky Institute of Chemical Kinetics & Combustion SB RAS; Institute of Solid State Chemistry & Mechanochemistry, Siberian Branch of the Russian Academy of Sciences; University of Alabama Tuscaloosa
    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.
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    The Endless World of Carotenoids-Structural, Chemical and Biological Aspects of Some Rare Carotenoids
    (MDPI, 2023) Polyakov, Nikolay E.; Focsan, A. Ligia; Gao, Yunlong; Kispert, Lowell D.; Voevodsky Institute of Chemical Kinetics & Combustion SB RAS; Valdosta State University; Nanjing Agricultural University; University of Alabama Tuscaloosa
    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.
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    ESI-MS and EPR spin trapping study of xanthophylls: structural and environmental impacts on reactivity
    (University of Alabama Libraries, 2015) Magyar, Adam S.; Kispert, Lowell D.; Bowman, Michael K.; University of Alabama Tuscaloosa
    Carotenoids are lipophilic pigments that provide many of the colors found in nature, including the colors found in plants, flowers, and animals. The main interest in carotenoids concerns their participation in light harvesting in biological systems and prevention of light-induced oxidative damage. Another reason for the interest in the redox properties of carotenoids is related to their use as antioxidants in medicinal formulations as a result of radical-mediated processes that occur frequently in living systems. A specific group of carotenoids, known as xanthophylls, are active in photoprotection and radical scavenging. What makes xanthophylls differ from other carotenoids is that they contain oxygen. This dissertation focuses on the interaction of three xanthophylls, Zeaxanthin, Lutein, and Astaxanthin, with damaging energetic species. Chapter 3 is focused on the deprotonation of naturally-occurring zeaxanthin (Zea) radical cations (Zea*+) to form neutral radicals (#Zea*) and their involvement in the qE portion of non-photochemical quenching (NPQ) in the model organism Arabidopsis thaliana. An H/D exchange method was developed to test for the presence of #Zea* and was detected via liquid chromatography/mass spectrometry (LC/MS) methods and analyzed using analysis of variance (ANOVA) techniques. Chapter 4 examined the characteristics of xanthophyll carotenoids which self-assemble in aqueous solution to form J- and H-type aggregates. This aggregation significantly changes the photo-physical and optical properties of these xanthophylls, and has an impact on solar energy conversion and light induced oxidative damage. This study applied electron paramagnetic resonance (EPR) and optical absorption spectroscopy to investigate how complexation can affect the aggregation ability of the three xanthophylls mentioned above, their photostability, and antioxidant activity. Chapter 5 demonstrates the different chemistries of geometrical isomers of zeaxanthin isolated from various sources in mass spectrometry using electrospray ionization sources. Zeaxanthin exhibits antioxidant activity and also plays a role in photo-protection in the retina. These properties have led to it being marketed as a dietary supplement as it is not formed by the body and must be consumed as part of the diet. Understanding the different chemical properties of zeaxanthin isomers is important with regards to the nutraceutical and pharmaceutical industries.
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    Photo Protection of Haematococcus pluvialis Algae by Astaxanthin: Unique Properties of Astaxanthin Deduced by EPR, Optical and Electrochemical Studies
    (MDPI, 2017) Focsan, A. Ligia; Polyakov, Nikolay E.; Kispert, Lowell D.; Valdosta State University; Voevodsky Institute of Chemical Kinetics & Combustion SB RAS; University of Alabama Tuscaloosa
    The antioxidant astaxanthin is known to accumulate in Haematococcus pluvialis algae under unfavorable environmental conditions for normal cell growth. The accumulated astaxanthin functions as a protective agent against oxidative stress damage, and tolerance to excessive reactive oxygen species (ROS) is greater in astaxanthin-rich cells. The detailed mechanisms of protection have remained elusive, however, our Electron Paramagnetic Resonance (EPR), optical and electrochemical studies on carotenoids suggest that astaxanthin's efficiency as a protective agent could be related to its ability to form chelate complexes with metals and to be esterified, its inability to aggregate in the ester form, its high oxidation potential and the ability to form proton loss neutral radicals under high illumination in the presence of metal ions. The neutral radical species formed by deprotonation of the radical cations can be very effective quenchers of the excited states of chlorophyll under high irradiation.
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    Reliable predictions of the properties of actinide complexes
    (University of Alabama Libraries, 2013) Jackson, Virgil Edward; Dixon, David A.; University of Alabama Tuscaloosa
    A study of reactions of laser-ablated thorium atoms and O2 using matrix isolation infrared spectroscopy has been conducted using electronic structure calculations to interpret the infrared spectra of three new thorium oxide species, ThO2-, Th2O2, and Th2O4 obtained in argon and neon matrixes. The potential energy surface for the reaction of matrix isolated ThO with CH4 to give the CH3Th(O)H intermediate has been calculated at the CCSD(T) level, it reveals that the CH3Th(O)H molecule possesses a pyramidal structure with a closed shell singlet ground state. Formation of the CH3Th-(O)H molecule from the reaction of ThO and methane has an energy barrier of 30 kcal/mol, which is consistent with the appearance of the 1CH3Th(O)H absorptions under broad band mercury arc UV irradiation. The 3Th + 1CH3OH asymptote is predicted to be 119 kcal/mol above the reactant asymptote, 1ThO + CH4, utilizing the spin orbit correction to the 3Th atom which is in excellent agreement with the value of 118.7 ± 3.8 kcal/mol. The first reliable predictions of the frequencies of the isolated uranyl ion have been made to develop new techniques to determine how this important form of uranium is being complexed in the environment. A comprehensive computational study of UO22+ complexed with the phosphate anions H2PO4-, HPO42-, and PO43- and water ligands has been performed at the density functional theory (DFT) and correlated molecular orbital theory levels in the gas phase and in aqueous solution. This study was done to aid the effort in developing solutions to the in situ remediation challenge posed by the nuclear waste stored in the tanks at the Hanford and Savannah River nuclear weapons production sites. This information can be used to provide a better understanding of the speciation of such species and to better our understanding of mobility issues of tank waste as well as stability concerns for waste matrices.
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    Supramolecular Carotenoid Complexes of Enhanced Solubility and Stability-The Way of Bioavailability Improvement
    (MDPI, 2019) Focsan, A. Ligia; Polyakov, Nikolay E.; Kispert, Lowell D.; Valdosta State University; Voevodsky Institute of Chemical Kinetics & Combustion SB RAS; Institute of Solid State Chemistry & Mechanochemistry, Siberian Branch of the Russian Academy of Sciences; University of Alabama Tuscaloosa
    Carotenoids are natural dyes and antioxidants widely used in food processing and in therapeutic formulations. However, their practical application is restricted by their high sensitivity to external factors such as heat, light, oxygen, metal ions and processing conditions, as well as by extremely low water solubility. Various approaches have been developed to overcome these problems. In particular, it was demonstrated that application of supramolecular complexes of "host-guest" type with water-soluble nanoparticles allows minimizing the abovementioned disadvantages. From this point of view, nanoencapsulation of carotenoids is an effective strategy to improve their stability during storage and food processing. Also, nanoencapsulation enhances bioavailability of carotenoids via modulating their release kinetics from the delivery system, influencing the solubility and absorption. In the present paper, we present the state of the art of carotenoid nanoencapsulation and summarize the data obtained during last five years on preparation, analysis and reactivity of carotenoids encapsulated into various nanoparticles. The possible mechanisms of carotenoids bioavailability enhancement by multifunctional delivery systems are also discussed.