Human intervention studies have provided clear evidence that dietary polyphenols (eg, flavonoids--eg, flavonols--and isoflavones) are at least partly absorbed and that they have the potential to exert biological effects. Biological activity of polyphenols is often assessed by using cultured cells as tissue models; in almost all such studies, cells are treated with aglycones or polyphenol-rich extracts (derived from plants and foods), and data are reported at concentrations that elicited a response. There are 2 inherent flaws in such an approach. First, plasma and tissues are not exposed in vivo to polyphenols in these forms. Several human studies have identified the nature of polyphenol conjugates in vivo and have shown that dietary polyphenols undergo extensive modification during first-pass metabolism so that the forms reaching the blood and tissues are, in general, neither aglycones (except for green tea catechins) nor the same as the dietary source. Polyphenols are present as conjugates of glucuronate or sulfate, with or without methylation of the catechol functional group. As a consequence, the polyphenol conjugates are likely to possess different biological properties and distribution patterns within tissues and cells than do polyphenol aglycones. Although deconjugation can potentially occur in vivo to produce aglycone, it occurs only at certain sites. Second, the polyphenol concentrations tested should be of the same order as the maximum plasma concentrations attained after a polyphenol-rich meal, which are in the range of 0.1-10 micromol/L. For correct interpretation of results, future efforts to define biological activities of polyphenols must make use of the available data concerning bioavailability and metabolism in humans.

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The human carboxylesterase 1 (CES1) gene encodes for the enzyme carboxylesterase 1, a serine esterase governing both metabolic deactivation and activation of numerous therapeutic agents. During the course of a study of the pharmacokinetics of the methyl ester racemic psychostimulant methylphenidate, profoundly elevated methylphenidate plasma concentrations, unprecedented distortions in isomer disposition, and increases in hemodynamic measures were observed in a subject of European descent. These observations led to a focused study of the subject's CES1 gene. DNA sequencing detected two coding region single-nucleotide mutations located in exons 4 and 6. The mutation in exon 4 is located in codon 143 and leads to a nonconservative substitution, p.Gly143Glu. A deletion in exon 6 at codon 260 results in a frameshift mutation, p.Asp260fs, altering residues 260-299 before truncating at a premature stop codon. The minor allele frequency of p.Gly143Glu was determined to be 3.7%, 4.3%, 2.0%, and 0% in white, black, Hispanic, and Asian populations, respectively. Of 925 individual DNA samples examined, none carried the p.Asp260fs, indicating it is an extremely rare mutation. In vitro functional studies demonstrated the catalytic functions of both p.Gly143Glu and p.Asp260fs are substantially impaired, resulting in a complete loss of hydrolytic activity toward methylphenidate. When a more sensitive esterase substrate, p-nitrophenyl acetate was utilized, only 21.4% and 0.6% catalytic efficiency (V(max)/K(m)) were determined in p.Gly143Glu and p.Asp260fs, respectively, compared to the wild-type enzyme. These findings indicate that specific CES1 gene variants can lead to clinically significant alterations in pharmacokinetics and drug response of carboxylesterase 1 substrates.

Feasibility studies are increasingly undertaken in preparation for randomised controlled trials in order to explore uncertainties and enable trialists to optimise the intervention or the conduct of the trial. Qualitative research can be used to examine and address key uncertainties prior to a full trial. We present guidance that researchers, research funders and reviewers may wish to consider when assessing or undertaking qualitative research within feasibility studies for randomised controlled trials. The guidance consists of 16 items within five domains: research questions, data collection, analysis, teamwork and reporting. Appropriate and well conducted qualitative research can make an important contribution to feasibility studies for randomised controlled trials. This guidance may help researchers to consider the full range of contributions that qualitative research can make in relation to their particular trial. The guidance may also help researchers and others to reflect on the utility of such qualitative research in practice, so that trial teams can decide when and how best to use these approaches in future studies.

It has been over 10 years since the first mention in a medical journal about cocoa and chocolate as potential sources of antioxidants for health. During this time, cocoa has been found to improve antioxidant status, reduce inflammation and correlate with reduced heart disease risk; with these results, and its popularity, it has received wide coverage in the press. However, after 10 years of research, what is known about the potential health benefits of cocoa and what are the important next steps in understanding this decadent source of antioxidants?

The health effects of dietary polyphenols might be explained by both intact compounds and their metabolites formed either in the tissues or in the colon by the microflora. The quantitative importance and biological activities of the microbial metabolites have seldom been examined in vivo. We measured the microbial metabolites formed in four groups of rats (n = 8) fed for 8 d a diet supplemented with 0.12 g/100 g catechin, 0.25 or 0.50 g/100 g red wine powder containing proanthocyanidins, phenolic acids, flavanols, anthocyanins and flavonols or an unsupplemented diet. Fourteen aromatic acid metabolites were assayed in urine collected for 24 h by an HPLC-electrospray ionization (ESI)-mass spectrometry (MS)-MS method. The three main metabolites formed from the catechin diet were 3-hydroxyphenylpropionic acid, 3-hydroxybenzoic acid and 3-hydroxyhippuric acid. Their total urinary excretion accounted for 4.7 g/100 g of the catechin ingested and that of intact catechins for 45.3 g/100 g. For wine polyphenols, the same microbial metabolites as observed for the catechin diet were identified in urine along with hippuric, p-coumaric, vanillic, 4-hydroxybenzoic and 3-hydroxyphenylacetic acids. All together, these aromatic acids accounted for 9.2 g/100 g of the total wine polyphenols ingested and intact catechins for only 1.2 g/100 g. The higher excretion of aromatic acids by rats fed wine polyphenols is likely due to their poor absorption in the proximal part of the gut. Some of the microbial metabolites still bear a reducing phenolic group and should also prevent oxidative stress in inner tissues. More attention should be given in the future to these microbial metabolites and their biological properties to help explain the health effects of polyphenols that are not easily absorbed through the gut barrier.

Phenolic compounds in foods have been associated with reduced incidences of heart disease by acting as antioxidants for low-density lipoprotein (LDL). Commercial prune and prune juice extracts (Prunus domestica cv. French) were analyzed for phenolics by reversed phase HPLC with diode array detection and tested for the ability to inhibit the Cu2+-catalyzed oxidation of human LDL. The mean concentrations of phenolics were 1840 mg/kg, 1397 mg/kg, and 441 mg/L in pitted prunes, extra large prunes with pits, and prune juice, respectively. Hydroxycinnamates, especially neochlorogenic acid, and chlorogenic acid predominated, and these compounds, as well as the prune and prune juice extracts, inhibited the oxidation of LDL. The pitted prune extract inhibited LDL oxidation by 24, 82, and 98% at 5, 10, and 20 μM gallic acid equivalents (GAE). The prune juice extract inhibited LDL oxidation by 3, 62, and 97% at 5, 10, and 20 μM GAE. These data indicate that prunes and prune juice may provide a source of dietary antioxidants. Keywords: Low-density lipoprotein (LDL); antioxidants; phenolics; neochlorogenic acid; prune; plum; Prunus domestica

Oxidative modification of low-density lipoprotein (LDL) is believed to play a crucial role in atherogenesis. The antioxidant activity of hydroxycinnamic acids typically present in fruits was investigated in vitro using a human LDL oxidation assay. The o-dihydroxy compounds caffeic, caftaric, chlorogenic, and neochlorogenic acids had highest antioxidant activities and inhibited LDL oxidation from 86 to 97% at 5 µM. Ferulic and fertaric acids had lower antioxidant activities, and p-coumaric and p-coutaric acids had the lowest. Differences in antioxidant activity were thus primarily related to the hydroxylation and methylation pattern. The esterification to tartaric acid slightly enhanced the antioxidant activity of p-coumaric and ferulic acids, but esterification of caffeic acid to quinic acid (as in chlorogenic and neochlorogenic acid) had no effect on or slightly decreased antioxidant activity. The observed differences in activities are discussed in terms of structural dissimilarities of the compounds. It is proposed that for the less active hydroxycinnamic acids, p-coumaric and ferulic acids, esterification to tartaric acid may enhance their ability to inhibit LDL oxidation by binding to apolipoprotein B in the LDL particle.