Health promotion by flavonoids, tocopherols, tocotrienols, and other phenols: direct or indirect effects? Antioxidant or not?
Top Cited Papers
Open Access
- 1 January 2005
- journal article
- review article
- Published by Elsevier in The American Journal of Clinical Nutrition
- Vol. 81 (1), 268S-276S
- https://doi.org/10.1093/ajcn/81.1.268s
Abstract
Foods and beverages rich in phenolic compounds, especially flavonoids, have often been associated with decreased risk of developing several diseases. However, it remains unclear whether this protective effect is attributable to the phenols or to other agents in the diet. Alleged health-promoting effects of flavonoids are usually attributed to their powerful antioxidant activities, but evidence for in vivo antioxidant effects of flavonoids is confusing and equivocal. This may be because maximal plasma concentrations, even after extensive flavonoid intake, may be low (insufficient to exert significant systemic antioxidant effects) and because flavonoid metabolites tend to have decreased antioxidant activity. Reports of substantial increases in plasma total antioxidant activity after flavonoid intake must be interpreted with caution; findings may be attributable to changes in urate concentrations. However, phenols might exert direct effects within the gastrointestinal tract, because of the high concentrations present. These effects could include binding of prooxidant iron, scavenging of reactive nitrogen, chlorine, and oxygen species, and perhaps inhibition of cyclooxygenases and lipoxygenases. Our measurements of flavonoids and other phenols in human fecal water are consistent with this concept. We argue that tocopherols and tocotrienols may also exert direct beneficial effects in the gastrointestinal tract and that their return to the gastrointestinal tract by the liver through the bile may be physiologically advantageous.Keywords
This publication has 138 references indexed in Scilit:
- Small molecule activators of sirtuins extend Saccharomyces cerevisiae lifespanNature, 2003
- Oxidative stress in cell culture: an under‐appreciated problem?FEBS Letters, 2003
- A Reevaluation of the Peroxynitrite Scavenging Activity of Some Dietary PhenolicsBiochemical and Biophysical Research Communications, 2000
- Bioavailability and efficiency of rutin as an antioxidant: a human supplementation studyEuropean Journal of Clinical Nutrition, 2000
- Lipid peroxidation, antioxidants and cardiovascular disease: how should we move forward?Cardiovascular Research, 2000
- Artifacts in Cell Culture: Rapid Generation of Hydrogen Peroxide on Addition of (−)-Epigallocatechin, (−)-Epigallocatechin Gallate, (+)-Catechin, and Quercetin to Commonly Used Cell Culture MediaBiochemical and Biophysical Research Communications, 2000
- The gastrointestinal tract: A major site of antioxidant action?Free Radical Research, 2000
- The generation and actions of isoprostanesBiochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism, 1997
- Inhibition of Peroxynitrite-Mediated Tyrosine Nitration by Catechin PolyphenolsBiochemical and Biophysical Research Communications, 1997
- Antioxidant and pro-oxidant actions of the plant phenolics quercetin, gossypol and myricetinBiochemical Pharmacology, 1989