Non-extractable polyphenols, a major dietary antioxidant: occurrence, metabolic fate and health effects

Abstract

Current research on dietary antioxidants misses the so-called non-extractable polyphenols (NEPP), which are not significantly released from the food matrix either by mastication, acid pH in the stomach or action of digestive enzymes, reaching the colon nearly intact. NEPP, not detected by the usual analytical procedures, are made up of macromolecules and single phenolic compounds associated with macromolecules. Therefore, NEPP are not included in food and dietary intake data nor in bioavailability, intervention or observational studies. The present paper aims to provide an overview of dietary NEPP -nature, occurrence in diet, metabolic fate and possible health effects. NEPP are a relevant fraction of dietary polyphenols exerting their main biological action in the colon, where they are extensively fermented by the action of microbiota, giving place to absorbable metabolites. NEPP exhibit different potential health-related properties, in particular in relation to gastrointestinal health, such as increases in antioxidant and antiproliferative capacities, reduction of intestinal tumorigenesis and modification of gene expression, as observed in different animal models. Further research into NEPP may provide a better understanding of the health effects of dietary antioxidants.

Macromolecular antioxidants or non-extractable polyphenols in fruit and vegetables: Intake in four European countries

“…After their colonic fermentation, they release metabolites that may either have a local beneficial effect or be absorbed, reaching paslma at longer times than soluble antioxidants and giving place to potential systemic effects, including imporvemnts in CVD risk factors. All these aspects wre recently reviewed (Pérez-Jiménez et al, 2013). Further studies should explore whether the differences in MACAN intake described here for different countries are associated with reduced risk for different chronic diseases.…”

“…Although studies of the health effects of NEPP are scarce, they have shown promising results in relation to gastrointestinal health (including colorectal cancer) and CVD (Pérez-Jiménez et al, 2013).…”

Juice by-products as a source of dietary fibre and antioxidants and their effect on hepatic steatosis

“…Hydrolysable tannins content (NEPP) was higher in mango, whereas peach and guava by-products presented the greatest values of condensed tannins. The NEPP from the juice byproducts could exert an important beneficial effect in the colon, promoting the intestinal health through the increase in antioxidant and antiproliferative capacities (Pérez-Jiménez et al, 2013).…”

“…The polyphenols can be absorbed in the small intestine (extractable polyphenols) (EPP), or reach colon along with other indigestible compounds like dietary fibre, resistant protein, starch, among others (nonextractable polyphenols) (NEPP). ADF can be fermented by bacterial microflora, and their metabolites have been reported to exert greater beneficial effects than their precursors (Pérez-Jiménez, Díaz-Rubio, & Saura-Calixto, 2013;Saura-Calixto, 2010). Therefore, sources of these nutraceutical compounds, such as juice by-products, are of great interest.…”

Regular Consumption of an Antioxidant-rich Juice Improves Oxidative Status and Causes Metabolome Changes in Healthy Adults

“…The particular antioxidant vehicle for the study (a commercial pomegranate and grape juice), as well as the dose, were chosen based on: a) dietary AC in Spain having decreased approximately 2000 μmol Trolox units per day since the 1960s [7], so this dose would be equivalent to a return to the traditional Mediterranean dietary pattern in terms of AC; b) a commercial processed product providing a standardized antioxidant content; and c) antioxidants from a beverage being more accessible in the small intestine than those from solid food, where a fraction of the polyphenols is associated with other components of the food matrix [19]. It is notable that for the ARJ chosen, this AC corresponds to a glass a day.…”