Health promotion by flavonoids, tocopherols, tocotrienols, and other phenols: direct or indirect effects? Antioxidant or not? Am J Clin Nutr 81:268S-276S

Department of Biochemistry, Faculty of Medicine, Singapore.
American Journal of Clinical Nutrition (Impact Factor: 6.77). 02/2005; 81(1 Suppl):268S-276S.
Source: PubMed

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.

1 Follower
12 Reads
    • "Later studies include techniques such as gas chromatography (Shindo et al., 1978) or liquid chromatography followed by UV detection (Hartley and Buchan, 1979; Vance et al., 1986). Due to the alleged health beneficiary properties of these compounds (Halliwell et al., 2005; Liu et al., 2000), a growing interest in analyzing phenolic acids and phenolic acid derivates in food and beverages has led to the development of numerous methods using liquid chromatography with UV, fluorometric, amperometric or mass spectrometric detection (Amakura et al., 2000; Chapuis-Lardy et al., 2002; Gruz et al., 2008; Jirovský et al., 2003; Määttä et al., 2003; Rodrı́guez-Delgado et al., 2001; Seeram et al., 2006) or gas chromatography followed by mass spectrometry (Chu et al., 2001). "
    [Show abstract] [Hide abstract]
    ABSTRACT: In this work the distribution of free and weekly adsorbed aromatic acids (phthalic acid and ten phenolic acids; gallic, p-hydroxybenzoic, salicylic, vanillic, protocatechuic, p-coumaric, syringic, sinapic, ferulic and caffeic acid), which could participate in weathering and soil formation processes, were studied for O, E and B horizons in a podzol soil in central Sweden. For the analysis a simple and rapid quantitative and qualitative liquid chromatography–tandem mass spectrometry method (using gradient elution) was developed with LODs ranging from 5 to 25 nM. Different soil solution sampling techniques (tension-lysimeter and soil centrifugation) and soil extraction with either 10 mM phosphate buffer (pH 7.2) or 50:50 (v/v) 10 mM phosphate buffer:MeOH were compared. All eleven acids were found in detectable or trace concentrations. The most abundant aromatic acids were vanillic and phthalic acid with concentrations around 1 μM for O and E horizon respectively. Lysimeter samples resulted in the lowest concentrations followed by centrifugation samples. In general, buffer:MeOH extraction resulted in the highest concentrations for the O horizon, likely due to MeOH's ability to compete for hydrophobic sites on soil organic matter (SOM). Then again, pure buffer with its higher ion strength, interfering with the acids electrostatic interactions with clay particles, leads to higher extracted concentrations for the E and B horizons. Since the efficiency of the extraction solutions, to a large extent, depends on the sample properties, a general approach is hard to appoint. However, the extraction of substituted cinnamic acids is in general facilitated by adding MeOH to the extraction solution. The use of statistical methods for the evaluation of the results showed a large and significant difference in aromatic acid concentrations received using different sampling techniques and sample preparations. In fact, sampling methods resulted in higher variations in aromatic acid concentrations than sampled horizon.
    Geoderma 11/2014; s 232–234:373–380. DOI:10.1016/j.geoderma.2014.06.005 · 2.77 Impact Factor
  • Source
    • "Hindawi Publishing Corporation e Scientific World Journal Volume 2014, Article ID 306217, 10 pages The Scientific World Journal of the body [10] [11] [12] "
    [Show abstract] [Hide abstract]
    ABSTRACT: The aim of this study was to determine the composition and content of phenolic compounds in the ethanol extracts of apple leaves and to evaluate the antioxidant activity of these extracts. The total phenolic content was determined spectrophotometrically, as well as the total flavonoid content in the ethanol extracts of apple leaves and the antioxidant activity of these extracts, by the ABTS, DPPH, and FRAP assays. The highest amount of phenolic compounds and flavonoids as well as the highest antioxidant activity was determined in the ethanol extracts obtained from the apple leaves of the cv. Aldas. The analysis by the HPLC method revealed that phloridzin was a predominant component in the ethanol extracts of the apple leaves of all cultivars investigated. The following quercetin glycosides were identified and quantified in the ethanol extracts of apple leaves: hyperoside, isoquercitrin, avicularin, rutin, and quercitrin. Quercitrin was the major compound among quercetin glycosides.
    The Scientific World Journal 09/2014; 2014. DOI:10.1155/2014/306217 · 1.73 Impact Factor
  • Source
    • "The microflora in the colon has enormous catalytic and hydrolytic potential. They will first cut down the glycogen of rutin to utilize as their carbon source (3) and can further catalyze the breakdown of the C6–C3–C6 flavonoid skeleton to a variety of phenolic acid catabolites (2, 4, 5). Thus, the bioactivity of polyphenol is very much dependent on its catabolism and catabolites that occur before absorption and disposition in target tissues and cells. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Part of quercetin flows into the colon after escaping the absorption of the small intestine and will be degraded by colonic microbiota. The catabolites in the colon partially determine the physiological activity of quercetin. Seven gut bacteria isolated from human feces were utilized to in vitro ferment quercetin. Their catabolites were analyzed with high-performance liquid chromatography and mass spectrometry, and the antioxidant activities of their fermented broths were compared with that of quercetin. One metabolite, 3,4-dihydroxyphenylacetic acid, was produced by both C. perfringens and B. fragilis transforming quercetin. No other metabolites were detected in the other fermented broths. The antioxidant activities of all strains fermenting quercetin reached the highest values at the concentration of 1 mg/mL quercetin in broth; the fermented products of C. perfringens and B. fragilis presented stronger activities than those of other strains at most concentrations of quercetin in broth. Additionally, all of the fermented broths presented a decline of the antioxidant activities compared to quercetin. Therefore, the antioxidant activity of quercetin will be lost when it reaches the human colon because of the gut bacterial fermentation. This is the first study to report that quercetin can be degraded by C. perfringens and B. fragilis and transformed to the same metabolite, 3,4-dihydroxyphenylacetic acid, and that antioxidant activities decline when quercetin is fermented by seven gut bacteria.
    Food & Nutrition Research 04/2014; 58. DOI:10.3402/fnr.v58.23406 · 1.79 Impact Factor
Show more