1,721,087 research outputs found
Lipid Peroxidation and Antioxidant Protection
Full text linkLipid peroxidation (LP) is the most important type of oxidative-radical damage in biological systems, owing to its interplay with ferroptosis and to its role in secondary damage to other biomolecules, such as proteins. The chemistry of LP and its biological consequences are reviewed with focus on the kinetics of the various processes, which helps understand the mechanisms and efficacy of antioxidant strategies. The main types of antioxidants are discussed in terms of structure–activity rationalization, with focus on mechanism and kinetics, as well as on their potential role in modulating ferroptosis. Phenols, pyri(mi)dinols, antioxidants based on heavy chalcogens (Se and Te), diarylamines, ascorbate and others are addressed, along with the latest unconventional antioxidant strategies based on the double-sided role of the superoxide/hydroperoxyl radical system
CHAPTER 11: Vitamin E. Inspired Synthetic Antioxidants
No full textThe search for novel antioxidants inspired by the structure of vitamin E was made possible by rationalization of the physical-chemical properties at the basis of vitamin E bioactivity and has contributed significantly to such rationalization. Hundreds of novel compounds have been synthesized and tested, a representative selection of which (51 molecules) is illustrated and discussed in this chapter, highlighting the structure-activity relationships behind their antioxidant activity. Among them, BO-653, thiatocopherol and related compounds, selenotocopherol and related compounds, tellurophenols, N-tocopherol and related compounds, and Mito-Vitamin E are given special attention. The discussion focuses on the absolute rate constant for trapping peroxyl radicals in solution. When available, the performance in biomimetic models, like the protection of low density lipoproteins, along with the results of in vivo testing for pharmaceutical applications is also addressed. Some of the synthetic analogues largely outperformed the most active natural α-tocopherol, both in model systems and in vivo. However, none of these compounds has yet reached medical practice or is currently approved as a pharmaceutical, which calls for further research
Antioxidant activities of vitamin E analogues in water and a Kamlet - Taft β-value for water
No full textRate constants for hydrogen atom abstraction from two water-soluble α-tocopherol (α-TOH, vitamin E) analogues by tert-butoxyl radicals have been measured at room temperature in four solvents, including water. The results imply that H-atom abstraction from α-TOH is 3.9 times slower in water than in benzene and yield a 'reliable' Kamlet-Taft β solvent parameter for water of 0.31. Literature rate constants for H-atom abstraction by peroxyl radicals from α-TOH in SDS micelles and in phospholipid micelles are, respectively, about 100 and 1000 times lower than in styrene. Since only a small fraction of the observed rate diminution can be attributed to hydrogen bonding of α-TOH to water it is concluded that in these heterogeneous systems much of the α-TOH is physically inaccessible to the attacking radicals. Whether this is also true for α-TOH in the biological membranes in living animals remains to be determined
Do Peroxyl Radicals Obey the Principle That Kinetic Solvent Effects on H-Atom Abstraction Are Independent of the Nature of the Abstracting Radical?
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Measurement of oxidative stress by EPR radical-probe technique
No full textAn EPR method for the measurement of the oxidative stress status in biological systems is described. The method is based on the X-band EPR detection of a persistent nitroxide generated under physiological or pseudo-physiological conditions by oxidation of a highly lipophylic hydroxylamine probe. The probe employed is bis(1-hydroxy-2,2,6,6-tetramethyl-4-piperidinyl)-decandioate which is administrated as hydrochloride salt. This probe is able to give a fast reaction with the majority of radical species involved in the oxidative stress. Furthermore, it crosses cell membranes and distributes in a biological environment without the need to alter or destroy compartmentation. The method is therefore suitable for quantitative measurements of ROS and can be applied to human tissues in real clinical settings. It has been successfully employed in systems of growing complexity and interest, ranging from subcellular fractions to whole animals and human liver. © 2001 Elsevier Science Inc
Plant Essential Oils as Healthy Functional Ingredients of Nutraceuticals and Diet Supplements: A Review
Full text linkEssential oils (EOs) are mixtures of volatile molecules endowed with health-promoting biological activities that go beyond their role as aromas and natural preservatives and can be exploited to develop functional foods and diet supplements. Their composition is briefly addressed along with regulatory aspects. The potential health benefit of human diet supplementation with EOs is outlined through a review of the recent literature on available clinical trials and preclinical research concerning EOs activity towards: (1) irritable bowel syndrome; (2) inflammatory bowel disease; (3) regulation of microbiota; (4) gastroprotection; (5) hepatoprotection; (6) protection of the urinary tract and diuresis; (7) management of metabolic disorders including hyperglycemia and hyperlipidemia; (8) anti-inflammatory and pain control; (9) immunomodulation and protection from influenza; and (10) neuroprotection and modulation of mood and cognitive performance. The emerging potential in such activities of selected EOs is given focus, particularly green and black cumin, bergamot, orange, myrtle, peppermint, sage, eucalyptus, lavender, thyme, lemon balm, ginger, and garlic
The role of sulfur and heavier chalcogens in the chemistry of antioxidants
No full textSulfur chemistry plays a central role in cellular redox homeostasis and cysteine-derived antioxidants like glutathione are the most abundant in biological systems. Inspired by Nature, the insertion of divalent sulfur as a substituent in phenolic antioxidants, e.g in thiatocopherol, seeking for improved antioxidant performance, has been an important strategy for long time. Replacement of sulfur with heavier chalcogens like Selenium and Tellurium has brought to even more performing antioxidants, able to quench peroxyl radical in a catalytic fashion and to express unusually high reactivity. On the other hand, natural bioactive compounds like plant-derived thiosulfinates (R-S(O)S-R) own their exceptional antioxidant properties to the ability of releasing sulfenic acids, whose antioxidant behavior has only recently been clarified. The chemistry and redox properties of unstable sulfenic acids (R-SOH), and analogous selenenic acids (R-SeOH) have also recently been elucidated, to better understand the properties of chalcogen-based natural antioxidants, and to develop novel bio-inspired compounds. This fascinating chemistry will be reviewed and the most significant achievement will be presented.[GRAPHICS]
Measuring Antioxidant Activity in Bioorganic Samples by the Differential Oxygen Uptake Apparatus: Recent Advances
No full textThe measure of O-2 consumption during the inhibited autoxidation of an easily oxidizable substrate is one of the most reliableand predictive methods to assess antioxidant activity, especially for structure-activity relationship studies, for food and industrial applications. The differential oxygen uptake apparatus described herein represents a powerful and cost-effective way to obtain antioxidant activity from inhibited autoxidation studies. These experiments provide the rate constant and the stoichiometry of the reaction between antioxidants and peroxyl radicals (ROO center dot), which are involved in the propagation of radical damage. We show the operation principles and the utility of this instrumentation in the bioorganic laboratory, with regard to the recent advances in this field, ranging from the study of natural antioxidants in biomimetic system, to the use of substrates generating hydroperoxyl radicals, and to the evaluation of novel nanoantioxidants
Solvent effects on the reactivity and free spin distribution of 2,2-diphenyl-1-picrylhydrazyl radicals
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