Antioxidants paradoxical effects

Increase in TAC is not always a good prognostic it may simply indicate an initial response to oxidative stress, as with concentrations of individual antioxidants and activities of antioxidant enzymes, or when it is due to disturbances in uric acid metabolism. Because uric acid is the main determinant of TAC of blood plasma, TAC increases in situations when the concentration of urate is increased, for example, in metabolic disorders and kidney failure. TAC is increased in urine from renal transplant recipients with delayed graft function (SI6). Ischemia of small intestine leads to an increase in TAC of rat blood serum, which is maximal (almost twofold) immediately after termination of 45-min ischemia (S22). TAC of blood plasma of rats poisoned with a high dose of carbon tetrachloride (1200 mg/kg, intraperitoneal injection, measurement 16 hr after injection) was significantly (over twofold) increased (Kl). These apparently paradoxical effects can be explained, however, by release of antioxidants from cells undergoing necrosis. Increase in TAC after intensive physical exercise also may be a marker of tissue... 

Patel, R. P., Boersma, B. J., Crawford, J. H., Hogg, N., Kirk, M., Kalyanaraman, B., Parks, D.A., Barnes, S., Darley-Usmar, V. (2001). Antioxidant mechanisms of isoflavones in lipid systems paradoxical effects of peroxyl radical scavenging. Free Radio. Biol Met/., 31(12), 1570-1581. 

People in France eat a lot of fatty foods but suffer less from fatal heart strokes than people in the northern regions of Europe or in North America, where wine is not consumed on a regular basis ( French paradox ). There is an increased favorable effect from red wine. The unique cardioprotective properties of red wine are due to the action of flavonoids, which are minimal in white wine. The best-researched flavonoids are resveratrol and quercetin, which confer antioxidant properties more potent than a-tocopherol. 

In a prospective study of 3454 men and women (age 55 years and older), a significant inverse association between the intake of catechin-rich tea and radiographically quantified aortic atherosclerosis was found [200], Similarly, inverse association between the consumption of red wine and CHD mortality (French paradox) have been suggested [201]. This beneficial effect of red wine may be due to the antioxidant ability of the wine phenolics to inhibit the oxidation of LDL to an atherogenic form [202],... 

Furthermore, polyphenolics present in wine, of which flavonoids are important components, have been suggested to be responsible of the so called French paradox, that is, the unexpectedly low rate of mortality from coronary heart disease in French population despite an unfavourable exposure to known cardiovascular risk factors such as high saturated fat consumption [19-21]. Epidemiological studies in USA [22] and Denmark [23] reported that moderate red wine drinkers had a lower risk of coronary artery disease than participants with no alcoholic beverage preference. However, controversial results about the antioxidant capacity of human serum after red wine consumption have been reported [24-27]. It is therefore uncertain whether wine constituents other than alcohol add to the cardioprotective effects of red wine. 

Paradoxically, chlorophyll was found to synergize the antioxidant effect of a-tocopherol in the dark (121), but chlorophyll degradation was found to contribute... 

Kirkwood s description is not wrong, but it is one-sided. His memorable simplicity conceals a can of worms. The molecular action of vitamin C is as simple and repetitive as flipping a coin, yet the effects are varied, unpredictable and utterly dependent on the milieu in which it operates. Just as flipping a coin leads to diametrically opposed outcomes, so too, vitamin C may on the one hand protect against illness and on the other kill tumours, or even people. The food chemist William Porter summed up the conundrum nicely, rising to an anguished eloquence rarely matched in scientific journals "Of all the paradoxical compounds, vitamin C probably tops the list. It is truly a two-headed Janus, a Dr Jekyll-Mr Hyde, an oxymoron of antioxidants."... 

DSM produces the antioxidant Resveratrol, the component in red wine that is responsible for a number of positive health effects also known as The French paradox . They have published a total synthesis of Resveratrol that is based on a Heck approach using acetylated intermediates (Scheme 13) [48, 49]. The best yield (94%) and highest substrate/catalyst ratio (2,000) were achieved using the palladacycle catalyst developed by Najera and co-workers [49, 50]. Hydrolysis of the tris-acetate provided Resveratrol in good yield. 

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