Biomarkers Of Polyphenol Intake Research Articles

A Molecularly Imprinted Polymer for Selective Extraction of Phenolic Acids from Human Urine

Studies for monitoring the bioavailability of dietary flavonoid compounds generate great interest. Among them, low-molecular-weight phenolic acids, secondary metabolites present in colonic catabolism and urinary excretion, have been proposed as biomarkers of polyphenol intake. Using 4-hydroxyphenylacetic acid as a template, a molecularly imprinted polymer (MIP) was synthesized for selective extraction of these hydroxylated metabolites from human urine samples and posterior analysis in an HPLC-DAD-MS system. Polymers were characterized by Scanning electron microscopy (SEM), Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), Brunauer-Emmett-Teller (BET) method, and binding experiments. MIP presents specific recognition ability for template and analogues molecules. This capacity of recognition and the pH dependence of the binding strength was also studied. The method was validated over a concentration range of 0.25–40 mg/L, r2 > 0.995. In the optimized conditions, the recovery value was 94% with RSD 1.2%. The Limit of Detection (LOD) and Limit of Quantification (LOQ) were 1.22 and 3.69 mg/L, respectively. In our knowledge, it is the first time that this methodology is applied to analyze urinary catabolites of the polyphenol compound and to provide a specific method and simple analysis alternative. The selective extraction of these metabolites improves the application and results obtained by other less sensitive analysis methods than the validation method. It also facilitates the development of new screening methods.

Phenolic sulfates as new and highly abundant metabolites in human plasma after ingestion of a mixed berry fruit purée.

Bioavailability studies are vital to assess the potential impact of bioactive compounds on human health. Although conjugated phenolic metabolites derived from colonic metabolism have been identified in the urine, the quantification and appearance of these compounds in plasma is less well studied. In this regard, it is important to further assess their potential biological activity in vivo. To address this gap, a cross-over intervention study with a mixed fruit purée (blueberry, blackberry, raspberry, strawberry tree fruit and Portuguese crowberry) and a standard polyphenol-free meal was conducted in thirteen volunteers (ten females and three males), who received each test meal once, and plasma metabolites were identified by HPLC-MS/MS. Sulfated compounds were chemically synthesised and used as standards to facilitate quantification. Gallic and caffeic acid conjugates were absorbed rapidly, reaching a maximum concentration between 1 and 2h. The concentrations of sulfated metabolites resulting from the colonic degradation of more complex polyphenols increased in plasma from 4h, and pyrogallol sulfate and catechol sulfate reached concentrations ranging from 5 to 20μm at 6h. In conclusion, phenolic sulfates reached high concentrations in plasma, as opposed to their undetected parent compounds. These compounds have potential use as biomarkers of polyphenol intake, and their biological activities need to be considered.

Urinary metabolites as biomarkers of polyphenol intake in humans: a systematic review

To identify associations between polyphenol intake and health and disease outcomes in cohort studies, it is important to identify biomarkers of intake for the various compounds commonly consumed as part of the diet. The objective of this systematic review was to assess the usefulness of polyphenol metabolites excreted in urine as biomarkers of polyphenol intake in humans. The method included a structured search strategy for polyphenol intervention studies on Ovid MEDLINE, EMBASE (Ovid), and Cochrane databases; formal inclusion and exclusion criteria; data extraction into an Access database; validity assessment; and meta-analysis. One hundred sixty-two controlled intervention studies with polyphenols were included, and mean recovery yield and correlations with the dose ingested were determined for 40 polyphenols. Polyphenols such as daidzein, genistein, glycitein, enterolactone, and hydroxytyrosol showed both a high recovery yield (12-37%) and a high correlation with the dose (Pearson's correlation coefficients: 0.67-0.87), which showed good sensitivity and robustness as biomarkers of intake throughout the different studies. Weaker recovery for anthocyanins (0.06-0.2%) and weaker correlations with dose [Pearson's correlation coefficients: 0.21-0.52 for hesperidin, naringenin, (-)-epicatechin, (-)-epigallocatechin, quercetin, and 3 microbial metabolites of isoflavones (dihydrodaidzein, equol, and O-desmethylangolensin)] suggest that they are currently less suitable as biomarkers of intake. These data confirm the value of certain urinary polyphenols as biomarkers of intake. A validation in populations is now needed to evaluate their specificity, sensitivity, and responsiveness to dose under free-living conditions.

Urinary excretion of 13 dietary flavonoids and phenolic acids in free-living healthy subjects – variability and possible use as biomarkers of polyphenol intake

Estimation of dietary intake of polyphenols is difficult, due to limited availability of food composition data and bias inherent to dietary assessment methods. The aim of the present study was to evaluate whether we could detect polyphenols and their metabolites in a spot urine sample in a free-living human population and whether it was related to those observed in 24-h urine samples, for potential use as a biomarkers of polyphenol intake. Four 24-h urine samples and two spot urine samples were collected from 154 participants of the SU.VI.MAX cohort (a randomized primary-prevention trial evaluating the effect of daily antioxidant supplementation on chronic diseases) in two separate studies over, respectively, a 7- and 2-day periods. Thirteen polyphenols and metabolites (chlorogenic acid (CGA), caffeic acid (CA), m-coumaric acid (mCOU), gallic acid (GA), 4-O-methylgallic acid (MeGA), quercetin (Q), isorhamnetin (MeQ), kaempferol (K), hesperetin (HESP), naringenin (NAR), phloretin (PHLOR), enterolactone (ENL) and enterodiol (END) were measured using HPLC-ESI-MS-MS. Correlations between the urinary excretion levels were observed. The most significant were explained by metabolic filiations (CGA/CA, CA/mCOU, GA/MeGA, Q/MeQ, NAR/PHLOR, ENL/END) or co-occurrence in a same food source (NAR/HESP). Concentrations in spot samples correlated with those in 24-h urine sample (P<0.02, except for CA and for MeQ). Intra-individual variations were smaller than inter-individual variations for all polyphenols (P<0.01) except for MeGA and for PHLOR. These results show that these polyphenols and metabolites are useful biomarkers for polyphenol intake.