http://www.dietcan.net/docs/Polifenoles%20en%20alimentos%20y%20biodisponibilidad.pdf

Polyphenols: food sources and bioavailability

Bioavailability and bioefficacy of polyphenols in humans. I. Review of 97 bioavailability studies

Brazilian plant extracts belonging to 16 species of 5 different families (71 extracts) were tested against the stable DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate) free-radical. The ability to scavenge DPPH radical was measured in these experiments by the discoloration of the solution. Ginkgo biloba and rutin, commonly used as antioxidants for medical purposes, were used as standards. Based on our results, we can say that as a general rule the ethanol extracts of plants belonging to the Verbenaceae family showed lower EC50 values than the other plant extracts. Among the partitions, the more polar ones (ethyl acetate and n-butanol) are those that generally have higher antioxidant activity (AA). Copyright © 2001 John Wiley & Sons, Ltd.

Screening of Brazilian plant extracts for antioxidant activity by the use of DPPH free radical method

Human intervention trials have provided evidence for protective effects of various (poly)phenol-rich foods against chronic disease, including cardiovascular disease, neurodegeneration, and cancer. While there are considerable data suggesting benefits of (poly)phenol intake, conclusions regarding their preventive potential remain unresolved due to several limitations in existing studies. Bioactivity investigations using cell lines have made an extensive use of both (poly)phenolic aglycones and sugar conjugates, these being the typical forms that exist in planta, at concentrations in the low-μM-to-mM range. However, after ingestion, dietary (poly)phenolics appear in the circulatory system not as the parent compounds, but as phase II metabolites, and their presence in plasma after dietary intake rarely exceeds nM concentrations. Substantial quantities of both the parent compounds and their metabolites pass to the colon where they are degraded by the action of the local microbiota, giving rise principally to small phenolic acid and aromatic catabolites that are absorbed into the circulatory system. This comprehensive review describes the different groups of compounds that have been reported to be involved in human nutrition, their fate in the body as they pass through the gastrointestinal tract and are absorbed into the circulatory system, the evidence of their impact on human chronic diseases, and the possible mechanisms of action through which (poly)phenol metabolites and catabolites may exert these protective actions. It is concluded that better performed in vivo intervention and in vitro mechanistic studies are needed to fully understand how these molecules interact with human physiological and pathological processes.

Dietary (Poly)phenolics in Human Health: Structures, Bioavailability, and Evidence of Protective Effects Against Chronic Diseases

Dietary phenolics: chemistry, bioavailability and effects on health.

Scavenging effects of tea catechins and their derivatives on 1,1-diphenyl-2-picrylhydrazyl radical

Products from tea catechins ((+)-catechin, (−)-epicatechin, (−)-epigallocatechin, (−)-epicatechin gallate, and (−)-epigallocatechin gallate) after heat treatment were individually isolated by preparative HPLC and subsequent crystallization. FAB-MS, elemental, 1H- and 13C-NMR, and optical rotation analyses indicated these products to be the C-2 epimers of the original catechins. The effects of temperature, time, pH, and concentration on this conversion of tea catechins to their epimers were examined. It was determined that the epimerization reaction should be conducted with 1% each of the tea catechin solution (pH5) at l20°C for 30 min.

Preparation of Epimers of Tea Catechins by Heat Treatment

Because a great deal of attention has been focused on the metabolism of (-)-epigallocatechin gallate (EGCg), quantitative analysis of this compound is required. For this purpose we developed a method of chemical synthesis of [4-(3)H]EGCg. Synthesized [4-(3)H]EGCg showed 99.5% radiochemical purity and a specific activity of 13 Ci/mmol. To clarify the excretion route of EGCg, the radioactivity levels of bile and urine were quantified after intravenous administration of [4-(3)H]EGCg to bile-duct-cannulated rats. Results showed that the radioactivity of the bile sample excreted within 48 h accounted for 77.0% of the dose, whereas only 2.0% of the dose was recovered in the urine. The excretion ratio of bile to urine was calculated to be about 97:3. These results clearly showed that bile was the major excretion route of EGCg. Time-course analysis of the radioactivity in blood was also performed to estimate the pharmacokinetic parameters following intravenous administration of [4-(3)H]EGCg. In addition, EGCg metabolites excreted in the bile within 4 h after the intravenous dose of [4-(3)H]EGCg were analyzed by HPLC. The results showed that 4',4"-di-O-methyl-EGCg was present in the conjugated form and made up about 14.7% of the administered radioactivity.

Synthesis of (-)-[4-3H]epigallocatechin gallate and its metabolic fate in rats after intravenous administration.

In the course of an exploratory investigation of antitumor-promoting catechins, 3-O-acyl-(+)-catechins of varying carbon lengths from C4 to C18 were assessed for inhibitory effects on the activation of the Epstein-Barr virus early antigen. Like 3-O-acyl-(−)-epigallocatechins, the (+)-catechin derivatives showed promising effects with the C-3 acyl chain of C8–C11 carbon atoms.

Inhibitory effects of 3-O-acyl-(+)-catechins on Epstein-Barr virus activation.

It is intended to provide a tea polyphenol composition which contains highly pure catechins and yet has relieved bitterness and astringency. Namely, a tea polyphenol composition: (A) containing from 85 to 95% by weight of catechins; (B) containing from 65 to 80% by weight of epigallocatechin gallate and gallocatechin gallate in the catechins; and (C) having a ratio (epigallocatechin gallate + gallocatechin gallate)/(epicatechin + catechin + epigallocatechin + gallocatechin + epicatechin gallate + catechin gallate) of from 2 to 4.

Ryota Seto

Papers

Scavenging effects of tea catechins and their derivatives on 1,1-diphenyl-2-picrylhydrazyl radical

Preparation of Epimers of Tea Catechins by Heat Treatment

Synthesis of (-)-[4-3H]epigallocatechin gallate and its metabolic fate in rats after intravenous administration.

Inhibitory effects of 3-O-acyl-(+)-catechins on Epstein-Barr virus activation.

Tea polyphenol composition and process for producing the same