Antioxidant preventive

Ascorbic acid—vitamin C—is an essential nutrient that the human body cannot manufacture from other compounds. It is needed for the formation of collagen, the protein that makes up connective tissue, and is essential to muscles, bones, cartilage, and blood vessels. It is a strong antioxidant, preventing damage from oxygen free radicals. 

However, this will also prevent the formation of other cytotoxic species such as the hydroxyl radical. Further evidence that antioxidants prevent against the development of I/R injury comes from studies that show that previous ischaemic injury in the small intestine of rats results in prevention of further damage on subsequent ischaemic challenge in association with measured increases in mucosal glutathione peroxidase and catalase (Osborne et al., 1992). 

Radiation is one of the most important known environmental stimuli of cancer development. This environmental factor becomes especially dangerous for humans living in the areas affected by irradiation from nuclear accidents. Earlier we found that the administration of a mixture of vitamin E and a-lipoic acid to children living in the area of Chernobyl nuclear accident significantly and synergistically suppressed leukocyte oxygen radical overproduction [211]. Thus a-lipoic acid and a-lipoic acid + vitamin E supplements may be of interest as antioxidant preventive agents for the treatment of radiation-induced cancer development. 

The obliteration of these iron-dependent oxidative processes by phytate suggests that this ubiquitous and abundant plant component functions as a natural antioxidant, preventing oxidative damage during storage of seeds. Surface treatment with phytic acid of various fruits and vegetables preserved their color, texture and flavor (7). Thus, dietary phytate may be a superior substitute for presently employed food preservatives, many of which pose significant health hazards. Additional applications of phytic acid are summarized in a recent review (34). 

Coskun O, Kanter M, Korkmaz A, Oter S. (2005) Quercetin, a flavonoid antioxidant, prevents and protects streptozotocin-induced oxidative stress and beta-cell damage in rat pancreas. Pharmacol Res 51 117-123. 

Various aromatic secondary amines, substituted phenols, and pyrazoli-dones (3) that function as traps for the propagating peroxy radicals gave dead-stop induction periods when used at a concentration of 50 p.p.m. An indication of the ease of oxidation of chloroprene is that 50 p.p.m. of 2,6-di-ferf-butyl-4-methylphenol gave an induction period of only 15 minutes, while the same concentration of antioxidant prevented n-hexadecane from oxidizing for 2 hours at 160°C. 

Antioxidants - prevent gum formation in fuel. The approved additives are generally phenolic based. Use is mandatory in aviation gasoline. Antioxidants are permitted in civil and military jet fuels. Antioxidants are mandatory in hydroprocessed British and U.S. military jet fuels as well as in international civil Jet A-l. 

Vitamin C [ascorbic acid) Men 90 mg/d Women 75 mg/d Cofactor for reactions requiring reduced copper or iron met-alloenzyme and as a protective antioxidant prevents scurvy Gastrointestinal disturbances, kidney stones, excess iron absorption... 

In rats, hepatic ischaemia is associated with reduced ATP levels but normal lipid peroxide formation. Reperfusion gives a slow recovery of ATP levels, a reduction in endogenous vitamin E and glutathione, but an increase in lipid peroxidation. Vitamin-E-treated animals showed accelerated ATP synthesis with a suppression of the increased lipid peroxidation [ 170, l7l]. Ischaemia of liver tissue reduced the metabolism of xenobiotics. Vitamin E was protectant against this effect [172]. The protective effect is related to an increase in catalytic activity of cytochrome P-450, to antioxidant and membrane-stabilizing properties [173]. In kidney tissue, prophylactic injection of vitamin E and synthetic antioxidants prevented the development of lesions during acute renal ischaemia and subsequent reperfusion. These effects were related therefore to the vitamin s antioxidant ability. 

A number of enzymes (antioxidants) prevent oxidative damage from the reactive products of oxygen that are formed during normal metabolic events. These are... 

Two principal classes of antioxidant are effective in thermal oxidation. Chainbreaking or primary antioxidants limit the rate of the chain propagation steps (Eqs. 3-2 and 3-3) by trapping carbon- or oxygen-centered free radicals. Hydroperoxide decomposing or secondary antioxidants prevent chain initiation by interfering with ROOH. Photoantioxidants protect plastics exposed to photo-oxidation. 

Crosslinked polyethylene. For additional investigations, LDPE samples were crosslinked by e-beam radiation with a dose of 250 kGy. In order to remove residual soluble components from the cross-linked LDPE samples, a suitable extraction process was developed [16], After being clamped in a frame, the polyethylene foils were extracted in m-xylene for 24 hours at a temperature of 80 °C. The addition of a small amount of BHT (2,6-di-tert-butyl-4-methylphenol), an antioxidant, prevented unwanted oxidation of the LDPE foils. Afterwards the samples were dried carefully at room temperature for 20 hours, and then dried in vacuo (20 mbar, 48 hours at 40 °C) to constant weight. 

Antioxidants Prevent oxidative Hindered phenolics (BHT), aromatic... 

E lipid-soluble antioxidant, prevents lipid oxidation of membranes, needed for healthy blood cells and tissues, blocks nitrosamine formation, protects PUFAs from autoxidation, important for normal immune fimction neuromuscular disorders, red blood ceU mpture (both uncommon) reduces risk of chronic disease (cardio-vascular, precancerous lesions, cancer), immunoenhancement, protec-tion from exercise-induced muscle injury, improves metaboHc control, re-duces risk of compHcations in diabetes... 

Carvedilol, a potent antioxidant, prevents the lipoperoxidation of mitochondrial membranes, which suggests a strong contribution to the known cardioprotective activity of this compound through protection of mitochondrial function. ... 

Antioxidants Prevent thermal and/or oxidative degradation Irganox 1010, Irgafos 168, BHT... 

Al-Malaika, S. Antioxidants preventive mechanisms. In Atmospheric Oxidation and Antioxidants, Scott, G., Ed. Elsevier Applied Science London, 1993 Vol. 1, 161-224. 

Linear-Low Density Polyethylene (LLDPE) and Ethylene -Propylene Diene (EPDM) Stabilization. Prevention of discoloration of LLDPE and EPDM are prime objectives in addition to thermal stabilization. While thermal stabilization is readily achieved by the use of phenolic antioxidants, prevention of discoloration requires a co-additive such as a phosphite. 

Antioxidants prevent the oxidation of the ftiel. Antioxidants work by interrupting the chain in free radical chain reaction by blocking the free radicals. Phen-ylenediamines are the most commonly used antioxidants. 

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