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

Abstract

Polyphenols are abundant micronutrients in our diet, and evidence for their role in the prevention of degenerative diseases is emerging. Bioavailability differs greatly from one polyphenol to another, so that the most abundant polyphenols in our diet are not necessarily those leading to the highest concentrations of active metabolites in target tissues. Mean values for the maximal plasma concentration, the time to reach the maximal plasma concentration, the area under the plasma concentration-time curve, the elimination half-life, and the relative urinary excretion were calculated for 18 major polyphenols. We used data from 97 studies that investigated the kinetics and extent of polyphenol absorption among adults, after ingestion of a single dose of polyphenol provided as pure compound, plant extract, or whole food/beverage. The metabolites present in blood, resulting from digestive and hepatic activity, usually differ from the native compounds. The nature of the known metabolites is described when data are available. The plasma concentrations of total metabolites ranged from 0 to 4 mumol/L with an intake of 50 mg aglycone equivalents, and the relative urinary excretion ranged from 0.3% to 43% of the ingested dose, depending on the polyphenol. Gallic acid and isoflavones are the most well-absorbed polyphenols, followed by catechins, flavanones, and quercetin glucosides, but with different kinetics. The least well-absorbed polyphenols are the proanthocyanidins, the galloylated tea catechins, and the anthocyanins. Data are still too limited for assessment of hydroxycinnamic acids and other polyphenols. These data may be useful for the design and interpretation of intervention studies investigating the health effects of polyphenols.

Free Radical Scavenging Properties of Skin and Pulp Extracts of Different Grape Cultivars In Vitro and Attenuation of H2O2-Induced Oxidative Stress in Liver Tissue Ex Vivo

“…Among the dietary antioxidants, the phenolic compounds, secondary metabolites occurring in plants, are the most abundant natural antioxidants [30]. They protect plants against harmful environmental conditions and are divided in two main categories, namely, flavonoids and nonflavonoids [31]. The significant correlation between the total polyphenol content and flavonoids content, as observed in this study, was also reported in other studies, in grape pomace extracts [32] and buckwheat extracts [33].…”

Antioxidant effects of ryegrass phenolics in lamb liver and plasma

“…It is also known that absorbed, low molecular weight phenolics, such as orcinol and quinol, can contribute to the digestible energy content of the diet without necessarily contributing to its nutritional value (Iason and Murray, 1996). Although it has been reported that dietary flavonoids (quercetin, genistein, catechin) are absorbed by humans (Paganga and Rice-Evans, 1997;Day et al, 2001;Manach et al, 2005), no phenolic compounds or any of the above metabolites could be detected, in our study, in the liver or plasma from lambs fed the grass diet. Three possible explanations may be offered to explain these findings.…”

Polymeric proanthocyanidins from Sicilian pistachio (Pistacia vera L.) nut extract inhibit lipopolysaccharide-induced inflammatory response in RAW 264.7 cells

“…Since only flavonol monomers and dimeric proanthocyanidins are absorbed [58][59][60][61], systemic effects of proanthocyanidins would be limited to these compounds or eventually to not yet characterized metabolites and/or colonic degradation products from the polymeric molecules [58]. In this context, our findings cannot help to rationalize the cardiovascular protection nor provide a molecular interpretation for the anti-inflammatory effects of pistachio nut diets [20].…”