Intestinal epithelial cell accumulation of the cancer preventive polyphenol ellagic acid--extensive binding to protein and DNA.
ABSTRACT Ellagic acid (EA), a polyphenol present in many berries, has been demonstrated to be preventive of esophageal cancer in animals both at the initiation and promotion stages. To be able to extrapolate these findings to humans we have studied the transcellular absorption and epithelial cell accumulation of [14C]EA in the human intestinal Caco-2 cells. The apical (mucosal) to basolateral (serosal) transcellular transport of 10 microM [14C]EA was minimal with a P(app) of only 0.13 x 10(-6)cm/s, which is less than for the paracellular transport marker mannitol. In spite of observations of basolateral to apical efflux, Caco-2 cell uptake studies showed high accumulation of EA in the cells (1054+/-136 pmol/mg protein), indicating facile absorptive transport across the apical membrane. Surprisingly, as much as 93% of the cellular EA was irreversibly bound to macromolecules (982+/-151 pmol/mg protein). To confirm the irreversible nature of the binding to protein, Caco-2 cells treated with 10 microM [14C]EA were subjected to SDS-PAGE analysis. This resulted in radiolabeled protein bands trapped in the stacking gel, consistent with [14C]EA-crosslinked proteins. Treatment of Caco-2 cells with 10 microM [14C]EA also revealed irreversible binding of EA to cellular DNA as much as five times higher than for protein (5020+/-773 pmol/mg DNA). Whereas the irreversible binding to protein required oxidation of EA by reactive oxygen species, this did not seem to be the case with the DNA binding. The avid irreversible binding to cellular DNA and protein may be the reason for its highly limited transcellular absorption. Thus, EA appears to accumulate selectively in the epithelial cells of the aerodigestive tract, where its cancer preventive actions may be displayed.
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ABSTRACT: Several aspects related to the antioxidant activity of ellagic acid were investigated using the Density Functional Theory. It was found that this compound is unusually versatile for protecting against the toxic effects caused by oxidative stress. Ellagic acid, in aqueous solution at physiological pH, is able of deactivating a wide variety of free radicals, which is a desirable capability since in biological systems these species are diverse. Under such conditions the ellagic acid anion is proposed as the key species for its protective effects. It is predicted to be efficiently, and continuously, regenerated after scavenging two free radicals per cycle. This is an advantageous and unusual behavior that contributes to increase its antioxidant activity at low concentrations. In addition, the ellagic acid metabolites are also capable of efficiently scavenging a wide variety of free radicals. Accordingly, it is proposed that the ellagic acid efficiency for that purpose is not reduced after being metabolized. On the contrary, it provides continuous protection against oxidative stress through a free radical scavenging cascade. This is an uncommon and beneficial behavior, which makes ellagic acid particularly valuable to that purpose. After deprotonation, ellagic acid is also able of chelating copper, in a concentration dependent way, decreasing the free radical production. In summary, ellagic acid is proposed to be an efficient multiple-function protector against oxidative stress.Chemical Research in Toxicology 04/2014; · 4.19 Impact Factor
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ABSTRACT: Psidium cattleianum, an unexploited Brazilian native fruit, is considered a potential source of bioactive compounds. In the present study, the in vitro scavenging capacity of skin and pulp extracts from P. cattleianum fruits against reactive oxygen species (ROS) and reactive nitrogen species (RNS) was evaluated by in vitro screening assays. Additionally, the composition of phenolic compounds and carotenoids in both extracts was determined by LC–MS/MS. The major phenolic compounds identified and quantified (dry matter) in the skin and pulp extracts of P. cattleianum were ellagic acid (2213–3818 μg/g extracts), ellagic acid deoxyhexoside (1475–2070 μg/g extracts) and epicatechin gallate (885–1603 μg/g extracts); while all-trans-lutein (2–10 μg/g extracts), all-trans-antheraxanthin (1.6–9 μg/g extracts) and all-trans-β-carotene (4–6 μg/g extracts) were the major carotenoids identified in both extracts. P. cattleianum pulp extract showed higher scavenging capacity than skin extract for all tested ROS and RNS. Considering the potential beneficial effects to human health, P. cattleianum may be considered as a good source of natural antioxidants and may be useful for the food and phytopharmaceutical industry.Food Chemistry 12/2014; 165:140–148. · 3.26 Impact Factor
- Acta Scientiarum Polonorum, Technologia Alimentaria 07/2014; 13(3):289-299.