Antioxidants small-molecule

Brain antioxidant defenses modify ischemia-reperfusion injury. The high metabolic rate ofbrain cells implies a high baseline ROS production, and brain cells possess high concentrations of both enzymatic and small-molecule antioxidant defenses. SOD1 may represent as much as 1% of total protein in brain it converts 02 to H202, which is then further metabolized to water and oxygen by... 

Small-molecule antioxidants include glutathione, ascorbic acid (vitamin C), vitamin E and a number of dietary flavonoids. Because humans, in contrast to most other animals, are unable to synthesize vitamin C, this important antioxidant must be supplied entirely from dietary intake. Other proteins, such as thioredoxin and metallothionein, may also contribute to some extent to the cellular antioxidant pool. 

Superoxide radical anion, hydroxyl radical, and hydrogen peroxide are known as prooxidants, whereas substances that neutralize their effects are called antioxidants. Oxidative stress occurs when the prooxidant-antioxidant balance becomes too favorable to the prooxidants. The effects of prooxidants can be neutralized by their direct reaction with small-molecule antioxidants, including glutathione, ascorbate, and tocopherols. In addition, oxidizing radicals are scavenged from a living system by several enzymes, including peroxidase, superoxide dismutase, and catalase. Oxidative lesions on DNA may be repaired by DNA repair enzymes. 

Plant foods contain a variety of PPs that are regarded as active agents and particularly as antioxidants. The chemical structures are quite complex and there are relatively small molecules such as hydrocinnamic acids (caffeic acid and ferulic acid) and also extremely large molecules like the proantho-... 

Dunlap, W. C. and Yamamoto, Y., Small-molecule antioxidants in marine organisms antioxidant activity of mycosporine-glycine, Comp. Biochem. Physiol., 112B, 105, 1995. 

Shick, J. M., Dunlap, W. C., and Carroll, A. K., Mycosporine-like amino acids and small-molecule antioxidants in Anthopleura spp. taxonomic and environmental patterns, Am. Zool., 36, 72A, 1996. 

C. A rule of thumb in small-molecule GPC is that it is possible to analyze two compounds whose molecular weight differs by 10% or more by the judicious selection of the mobile phase. For instance, the separation of tolnaftate (the active ingredient of an antifungal preparation) (MW = 302) and BHT (which is present as an antioxidant) (MW = 220) can be accomplished using methylene chloride, a nonhydrogen bonding solvent as shown in Figure 11-4. For this assay, sample prep-... 

Figure 5 Structures of small-molecule inhibitors of nonapoptotic cell death. Inhibitors of (a-e) PARP-1, (f) HSP90, (i, j) mitochondrial respiratory complexes I and (k) complexes 2, (I) phosphatidylcholine-specific phospholipase C, (m) acid sphingomyelinase, (n) NADPH oxidase, (o) JNK kinase, (p-s) necroptosis, (t-w) MPTP, and (g, h) antioxidants, (a) 3-aminobenzamide, (b) benadrostin, (c) Nu1025, 8-hydroxy-2-methylquinazolin-4(3H)-one,...

Some examples of small-molecule antioxidants are a-tocopherol (vitamin E 5.24), which is found dissolved in cell membranes and protects them against lipid peroxidation, and ascorbate (vitamin C 5.25) and glutathione (5.26), which are found in the cytosol of many cells. Several others are known as well. ... 

Details about structure, biosynthesis, and classification of phenolics are described in the other chapters in this handbook. Plant phenolics have a distinctive ability to form non-covalent, intermolecular complexes with each other and with both large and small molecules. Recognition of the antioxidant activities of many polyphenols has established correlation with the health benefits by such compounds [34]. This leads to the development of commercial products containing free-radical-scavenging phytochemical mixtures, for example, Pycnogenol (procyanidin extracted from Pinus maritima). Table 82.2 represents a list of polyphenolic compounds used in nutraceuticals and their biologic effects on human health. 

If LDL oxidation plays a central role in atherogenesis, antioxidants that can prevent LDL oxidation should prevent or slow the atherosclerotic process. Hence, many basic research studies have investigated how effectively and by what mechanisms the endogenous antioxidants in human plasma and LDL inhibit lipid peroxidation and oxidative modification of LDL. Human plasma, the transport medium for LDL, contains a vast array of defense mechanisms, including small molecule antioxidants and metal-binding proteins (reviewed in Stocker and Frei, 1991 Frei,... 

Frei, B., Stocker, R., and Ames, B. N., 1992, Small molecule antioxidant defenses in human extracellular fluids, in The Molecular Biology of Free Radical Scavenging Systems (J. Scandalios, ed.), pp. 23-45, Cold Spring Harbor Laboratory Press, Cold Spring Harbor. 

Vitamin E has a long alkyl chain and is therefore hydrophobic, making it capable of reaching the hydrophobic regions of cell membranes. Vitamin C is a small molecule with multiple OH groups, rendering it water soluble. It functions as an antioxidant in hydrophihc regions, such as in blood. 

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